Over the past ten years, both abroad and in our country, the number of purulent-inflammatory diseases due to infections that have acquired the name “nosocomial infections” (HAI) has increased, as defined by the World Health Organization (WHO). Based on the analysis of diseases caused by nosocomial infections, we can say that their duration and frequency directly depend on the state of the air environment hospital premises. In order to ensure the required microclimate parameters in operating rooms (and industrial clean rooms), unidirectional flow air distributors are used. As the control results showed environment and analysis of the movement of air flows, the operation of such distributors can provide the required microclimate parameters, but negatively affects the bacteriological composition of the air. To achieve the required degree of protection of the critical zone, it is necessary that the air flow that leaves the device does not lose the shape of its boundaries and maintains straightness of movement, in other words, the air flow should not narrow or expand over the zone selected for protection in which the surgical table is located.
In the structure of a hospital building, operating rooms require the greatest responsibility due to the importance of the surgical process and ensuring necessary conditions microclimate so that this process is successfully carried out and completed. The main source of release of various bacterial particles is directly medical staff, which generates particles and releases microorganisms as it moves around the room. The intensity of the appearance of new particles in the air space of a room depends on the temperature, the degree of mobility of people, and the speed of air movement. The nosocomial infection, as a rule, moves around the operating room with air currents, and the probability of its penetration into the vulnerable wound cavity of the patient being operated on never decreases. As observations have shown, improper organization of ventilation systems usually leads to such a rapid accumulation of infection in the room that its level can exceed permissible norm.
For several decades now, foreign experts have been trying to develop system solutions to ensure the necessary air conditions in operating rooms. The air flow that enters the room must not only maintain microclimate parameters, but also assimilate harmful factors(heat, smell, humidity, harmful substances), but also to maintain the protection of selected areas from the possibility of infection entering them, and therefore to ensure the required cleanliness of operating room air. The area in which invasive operations are performed (penetration into the human body) is called the "critical" or operating zone. The standard defines such a zone as an “operating sanitary protection zone”; this concept means the space in which the operating table, equipment, tables for instruments, and medical personnel are located. There is such a thing as a “technological core”. It refers to the area in which production processes under sterile conditions, this area can be meaningfully correlated with the operating room.
In order to prevent the penetration of bacterial contamination into the most critical areas, screening methods based on the use of air flow displacement have become widespread. For this purpose, laminar air flow air distributors have been developed with different design. Later, "laminar" became known as "unidirectional" flow. Today you can meet the most different variants names of air distribution devices for clean rooms, for example, “laminar ceiling”, “laminar”, “operating system” clean air", "operational ceiling" and others, but this does not change their essence. The air distributor is built into the ceiling structure above the protected area of the room. He can be various sizes, it depends on the air flow. Optimal area such a ceiling should not be less than 9 m2 so that it can completely cover the area with tables, staff and equipment. The displacing air flow in small portions slowly flows from top to bottom, thus separating the aseptic field of the surgical exposure zone, the zone where sterile material is transferred from the environmental zone. Air is removed from the lower and upper zones of the protected room simultaneously. HEPA filters (class H according to) are built into the ceiling, which allow air flow through them. Filters only trap living particles without disinfecting them.
Recently, at the global level, attention has increased to the issues of disinfecting the air environment of hospital premises and other institutions in which sources of bacterial contaminants are present. The documents set out the requirements that it is necessary to disinfect the air in operating rooms with a particle deactivation efficiency of 95% or higher. Climate system equipment and air ducts are also subject to disinfection. Bacteria and particles released by surgical personnel continuously enter the room air and accumulate there. In order to prevent the concentration of harmful substances in the room from reaching the maximum permissible level, it is necessary to constantly monitor the air environment. This control is mandatory after installation. climate system, repair or Maintenance, that is, while the cleanroom is in use.
It has already become commonplace for designers to use ultra-fine unidirectional flow air distributors with built-in ceiling-type filters in operating rooms.
Air flows with large volumes slowly move down the room, thus separating the protected area from the surrounding air. However, many specialists do not worry that these solutions alone will not be enough to maintain the required level of air disinfection during surgical operations.
A large number of design options for air distribution devices have been proposed, each of them has its own application in a specific area. Special operating rooms within their class are divided into subclasses depending on their purpose according to the degree of cleanliness. For example, cardiac surgery, general, orthopedic operating rooms, etc. Each class has its own requirements for ensuring cleanliness.
For the first time, air distributors for clean rooms were used in the mid-50s of the last century. Since then, the distribution of air in industrial premises has become traditional in cases where it is necessary to ensure reduced concentrations of microorganisms or particles, all this is done through a perforated ceiling. The air flow moves in one direction through the entire volume of the room, while the speed remains uniform - approximately 0.3 - 0.5 m/s. The air is supplied through a group of high efficiency air filters located on the ceiling of the clean room. The air flow is supplied according to the principle of an air piston, which rapidly moves down through the entire room, removing harmful substances and contaminants. Air is removed through the floor. This air movement can remove aerosol contaminants originating from processes and personnel. The organization of such ventilation is aimed at ensuring required cleanliness operating room air. Its disadvantage is that it requires a large air flow, which is not economical. For cleanrooms of class ISO 6 (according to ISO classification) or class 1000, an air exchange rate of 70-160 times per hour is allowed. Later they were replaced by more efficient devices modular type, having smaller dimensions and low costs, which allows you to choose an air supply device based on the size of the protection zone and the required air exchange rates in the room, depending on its purpose.
Operation of laminar air diffusers
Laminar flow devices are designed for use in clean production rooms for distributing large volumes of air. Implementation requires specially designed ceilings, room pressure regulation and floor hoods. If these conditions are met, laminar flow distributors will certainly create the necessary unidirectional flow with parallel flow lines. Due to the high air exchange rate, conditions close to isothermal are maintained in the supply air flow. Designed for air distribution with extensive air exchanges, ceilings provide low starting flow rates due to their large area. Control of changes in air pressure in the room and the result of the operation of exhaust devices provide minimum dimensions air recirculation zones, the “one pass and one exit” principle works here. Suspended particles fall to the floor and are removed, making recycling virtually impossible.
However, in an operating room, such air heaters work somewhat differently. In order not to exceed the permissible levels of bacteriological purity of the air in operating rooms, according to calculations, air exchange values are about 25 times per hour, and sometimes even less. In other words, these values are not comparable to the values calculated for production premises. To maintain stable air flow between the operating room and adjacent rooms, the operating room maintains overpressure. Air is removed through exhaust devices, which are installed symmetrically in the walls of the lower zone. To distribute smaller volumes of air, laminar flow devices of a smaller area are used; they are installed directly above the critical area of the room as an island in the middle of the room, rather than occupying the entire ceiling.
Based on observations, such laminar air distributors will not always be able to provide unidirectional flow. Since a difference of 5-7 °C between the temperature in the supply air stream and the ambient air temperature is inevitable, the air leaving the air supply device, will descend much faster than a unidirectional isothermal flow. This is a common occurrence for ceiling diffusers installed in public spaces. The opinion that laminar floors provide a unidirectional, stable air flow in any case, regardless of where and how they are used, is erroneous. Indeed, in real conditions, the speed of a vertical low-temperature laminar flow will increase as it descends towards the floor.
With increasing volume supply air and by reducing its temperature relative to the room air, the acceleration of its flow increases. As shown in the table, thanks to the use of a laminar system with an area of 3 m 2 and a temperature difference of 9 ° C, the air speed at a distance of 1.8 m from the outlet increases three times. At the exit from the laminar device, the air speed is 0.15 m/s, and in the area of the operating table - 0.46 m/s, which exceeds permissible level. Many studies have long proven that with an increased speed of the inflow flow, its “unidirectionality” is not maintained.
| Air consumption, m 3 / (h m 2) | Pressure, Pa | Air speed at a distance of 2 m from the panel, m/s | |||||
| 3 °С T | 6 °С T | 8 °С T | 11 °С T | NC | |||
| Single panel | 183 | 2 | 0,10 | 0,13 | 0,15 | 0,18 | <20 |
| 366 | 8 | 0,18 | 0,20 | 0,23 | 0,28 | <20 | |
| 549 | 18 | 0,25 | 0,31 | 0,36 | 0,41 | 21 | |
| 732 | 32 | 0,33 | 0,41 | 0,48 | 0,53 | 25 | |
| 1.5 – 3.0 m2 | 183 | 2 | 0,10 | 0,15 | 0,15 | 0,18 | <20 |
| 366 | 8 | 0,18 | 0,23 | 0,25 | 0,31 | 22 | |
| 549 | 18 | 0,25 | 0,33 | 0,41 | 0,46 | 26 | |
| 732 | 32 | 0,36 | 0,46 | 0,53 | – | 30 | |
| More than 3 m2 | 183 | 2 | 0,13 | 0,15 | 0,18 | 0,20 | 21 |
| 366 | 8 | 0,20 | 0,25 | 0,31 | 0,33 | 25 | |
| 549 | 18 | 0,31 | 0,38 | 0,46 | 0,51 | 29 | |
| 732 | 32 | 0,41 | 0,51 | – | – | 33 | |
An analysis of air control in operating rooms by Lewis (1993) and Salvati (1982) found that in some cases the use of laminar flow units with high air velocities increases the level of airborne contamination in the area of the surgical incision, which can lead to to its infection.
The dependence of the change in air flow speed on the supply air temperature and the size of the laminar panel area is shown in the table. When air moves from the starting point, the flow lines will run parallel, then the boundaries of the flow will change, narrowing towards the floor will occur, and, therefore, it will no longer be able to protect the area determined by the dimensions of the laminar flow unit. Having a speed of 0.46 m/s, the air flow will capture the low-moving air of the room. And since bacteria are continuously entering the room, contaminated particles will enter the air flow coming out of the supply unit. This is facilitated by air recirculation, which occurs due to air pressure in the room.
To maintain the cleanliness of operating rooms, according to the standards, it is necessary to ensure air imbalance by increasing the inflow by 10% more than the exhaust. Excess air enters adjacent, untreated rooms. In modern operating rooms, sealed sliding doors are often used, then excess air cannot escape and circulates throughout the room, after which it is taken back into the supply unit using built-in fans, then it is cleaned in filters and re-supplied into the room. The circulating air flow collects all contaminated substances from the air in the room (if it moves near the supply flow, it can pollute it). Since the boundaries of the flow are violated, it is inevitable that air from the room will be mixed into it, and, consequently, the penetration of harmful particles into the protected sterile zone.
Increased air mobility entails intensive exfoliation of dead skin particles from open areas of the skin of medical personnel, after which they enter the surgical incision. However, on the other hand, the development of infectious diseases during the rehabilitation period after surgery is a consequence of the patient’s hypothermic state, which is aggravated when exposed to moving currents of cold air. So, a well-functioning traditional laminar flow air diffuser in a cleanroom can be as beneficial as it can be detrimental during an operation performed in a conventional operating room.
This feature is typical for laminar flow devices with an average area of about 3 m2 - optimal for protecting the operating area. According to American requirements, the air flow rate at the outlet of a laminar flow device should not be higher than 0.15 m/s, that is, 14 l/s of air should enter the room from an area of 0.09 m2. In this case, 466 l/s (1677.6 m 3 / h) or about 17 times per hour will flow. Since, according to the standard air exchange rate in operating rooms, it should be 20 times per hour, according to - 25 times per hour, then 17 times per hour fully corresponds to the required standards. It turns out that the value of 20 times per hour is suitable for a room with a volume of 64 m 3.
According to current standards, the area of general surgery (standard operating room) should be at least 36 m 2. However, higher demands are placed on operating rooms intended for more complex operations (orthopedic, cardiological, etc.), often the volume of such operating rooms is about 135 - 150 m 3 . For such cases, an air distribution system with a larger area and air capacity will be required.
If air flow is provided for larger operating rooms, this creates the problem of maintaining laminar flow from the outlet level to the operating table. Air flow studies were conducted in several operating rooms. In each of them, laminar panels were installed, which can be divided into two groups based on the occupied area: 1.5 - 3 m 2 and more than 3 m 2, and experimental air conditioning installations were built that allow you to change the value of the supply air temperature. During the study, measurements were taken of the speed of the incoming air flow at various air flow rates and temperature changes; these measurements can be seen in the table.
Criteria for the cleanliness of operating rooms
To properly organize the circulation and distribution of air in the room, it is necessary to select a rational size of the supply panels, ensure the standard flow rate and temperature of the supply air. However, these factors do not guarantee absolute air disinfection. For more than 30 years, scientists have been solving the issue of disinfecting operating rooms and proposing various anti-epidemiological measures. Today, the requirements of modern regulatory documents for the operation and design of hospital premises face the goal of air disinfection, where the main way to prevent the accumulation and spread of infections is HVAC systems.
For example, according to the standard, the main purpose of its requirements is disinfection, and it states that “a properly designed HVAC system minimizes the airborne spread of viruses, fungal spores, bacteria and other biological contaminants”, a major role in the control of infections and other harmful factors HVAC system plays. It defines requirements for indoor air conditioning systems, which state that the design of the air supply system should minimize the penetration of bacteria along with the air into clean areas, and maintain the highest possible level of cleanliness in the remainder of the operating room.
However, regulatory documents do not contain direct requirements reflecting the determination and control of the effectiveness of disinfection of premises with various ventilation methods. Therefore, when designing, you have to engage in searches, which take a lot of time and do not allow you to do your main work.
A large amount of regulatory literature has been produced on the design of HVAC systems for operating rooms; it describes requirements for air disinfection that are quite difficult for the designer to meet for a variety of reasons. To do this, it is not enough just to know modern disinfecting equipment and the rules for working with it; you also need to maintain further timely epidemiological monitoring of indoor air, which creates an impression of the quality of operation of HVAC systems. This, unfortunately, is not always observed. If the assessment of the cleanliness of industrial premises is based on the presence of particles (suspended substances), then the indicator of cleanliness in clean hospital premises is represented by live bacterial or colony-forming particles, their permissible levels are given in. In order not to exceed these levels, regular monitoring of indoor air is necessary for microbiological indicators; this requires counting microorganisms. The collection and calculation methodology for assessing the level of air cleanliness was not given in any regulatory document. It is very important that the counting of microorganisms should be carried out in the work area during the operation. But this requires a ready-made design and installation of an air distribution system. The degree of disinfection or the effectiveness of the system cannot be determined before starting work in the operating room; this is established only during at least several operations. Here a number of difficulties arise for engineers, because the necessary research contradicts the observance of anti-epidemic discipline in hospital premises.
Air curtain method
Properly organized joint work of air supply and removal ensures the required air conditions in the operating room. To improve the nature of air flow in the operating room, it is necessary to ensure a rational relative position of exhaust and supply devices.
Rice. 1. Analysis of the air curtain operation
Using both the entire ceiling area for air distribution and the entire floor for exhaust is not possible. Exhaust units on the floor are unhygienic as they quickly become dirty and difficult to clean. Complex, bulky and expensive systems are not widely used in small operating rooms. Therefore, the most rational is considered to be the “island” placement of laminar panels above the protected area and the installation of exhaust openings in the lower part of the room. This makes it possible to organize air flows similar to clean industrial premises. This method is cheaper and more compact. Air curtains are successfully used to act as a protective barrier. The air curtain is connected to the flow of supply air, forming a narrow “shell” of air at a higher speed, which is specially created along the perimeter of the ceiling. Such a curtain constantly works for exhaust and prevents polluted ambient air from entering the laminar flow.
To better understand how an air curtain works, you can imagine an operating room with a hood installed on all four sides of the room. The air flow, which comes from the “laminar island” located in the center of the ceiling, can only go down, while expanding towards the sides of the walls as it approaches the floor. This solution will reduce recirculation zones and the size of stagnation areas where harmful microorganisms accumulate, prevent room air from mixing with laminar flow, reduce its acceleration, stabilize speed and block the entire sterile zone with downward flow. This helps to isolate the protected area from the surrounding air and allows biological contaminants to be removed from it.
Rice. Figure 2 shows a standard air curtain design with slits around the perimeter of the room. If you organize an exhaust along the perimeter of the laminar flow, it will stretch, the air flow will expand and fill the entire area under the curtain, and as a result, the “narrowing” effect will be prevented and the required speed of the laminar flow will be stabilized.
Rice. 2. Air curtain diagram
In Fig. Figure 3 shows the actual air speed values for a properly designed air curtain. They clearly show the interaction of the air curtain with a laminar flow that moves uniformly. An air curtain allows you to avoid installing a bulky exhaust system along the entire perimeter of the room. Instead, as is customary in operating rooms, a traditional hood is installed in the walls. The air curtain serves to protect the area surrounding the surgical personnel and the table, preventing contaminated particles from returning to the initial air flow.
Rice. 3. Actual velocity profile in the air curtain cross section
What level of disinfection can be achieved using an air curtain? If it is poorly designed, it will not provide any greater effect than a laminar system. You can make a mistake at high air speed, then such a curtain can “pull” the air flow faster than necessary, and it will not have time to reach the operating table. Uncontrolled flow behavior can threaten the penetration of contaminated particles into the protected area from floor level. Also, a curtain with insufficient suction speed will not be able to completely block the air flow and may be drawn into it. In this case, the air mode of the operating room will be the same as when using only a laminar device. During design, the speed range must be correctly identified and the appropriate system selected. The calculation of disinfection characteristics depends on this.
Air curtains have a number of obvious advantages, but they should not be used everywhere, because it is not always necessary to create a sterile flow during surgery. The decision on the level of air disinfection required is made jointly with the surgeons involved in these operations.
Conclusion
Vertical laminar flow does not always behave predictably, which depends on the conditions of its use. Laminar flow panels, which are used in clean production rooms, often do not provide the required level of disinfection in operating rooms. The installation of air curtain systems helps control the movement patterns of vertical laminar air flows. Air curtains help to carry out bacteriological control of air in operating rooms, especially during long-term surgical interventions and the constant presence of patients with weak immune systems, for whom airborne infections are a huge risk.
The article was prepared by A. P. Borisoglebskaya using materials from the ASHRAE journal.
Literature
- SNiP 2.08.02–89*. Public buildings and structures.
- SanPiN 2.1.3.1375–03. Hygienic requirements for the placement, design, equipment and operation of hospitals, maternity hospitals and other medical hospitals.
- Instructional and methodological guidelines for organizing air exchange in ward departments and operating rooms of hospitals.
- Instructional and methodological guidelines on hygienic issues in the design and operation of infectious diseases hospitals and departments.
- Manual for SNiP 2.08.02–89* for the design of healthcare facilities. GiproNIIZdrav of the USSR Ministry of Health. M., 1990.
- GOST ISO 14644-1–2002. Cleanrooms and associated controlled environments. Part 1. Classification of air purity.
- GOST R ISO 14644-4–2002. Cleanrooms and associated controlled environments. Part 4. Design, construction and commissioning.
- GOST R ISO 14644-5–2005. Cleanrooms and associated controlled environments. Part 5. Operation.
- GOST 30494–96. Residential and public buildings. Indoor microclimate parameters.
- GOST R 51251–99. Air purification filters. Classification. Marking.
- GOST R 52539–2006. Air purity in medical institutions. General requirements.
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- Methodical instructions. MU 2.6.1.1892-04. Hygienic requirements for ensuring radiation safety when conducting radionuclide diagnostics using radiopharmaceuticals. Classification of health care facilities premises.
Operating room microclimate. When ventilating operating rooms, the relative humidity in the room must be maintained within 50 - 60%, air mobility 0.15 - 0.2 m/s and temperature 19 - 21 ° C in the warm period and 18 - 20 ° C in the cold period. The most effective and modern way of ventilating operating rooms, from the point of view of combating dust and bacterial air pollution, is to equip operating rooms with laminar air flow, which can be supplied in a horizontal or vertical direction. Vertical flow supply is preferable, as it allows, at normal air speeds, to achieve 500 - 600-fold exchange per hour.
Heating operating room It is better to organize water, radiation with panels on the ceiling, walls or built into the floor.
Ensuring air purity in the operating room. In the spread of hospital infections, airborne droplets are of greatest importance, and therefore great attention should be paid to constantly ensuring the cleanliness of the air in the premises of a surgical hospital and operating unit.
The main component that pollutes the air in a surgical hospital and operating unit is finely dispersed dust on which microorganisms are sorbed. Sources of dust are mainly ordinary and special clothing of patients and staff, bedding, the entry of soil dust with air currents, etc. Therefore, measures aimed at reducing the contamination of the air in the operating room primarily involve reducing the influence of sources of contamination on the air.
Persons with septic wounds or any purulent skin contamination are not allowed to work in the operating room.
Staff must shower before surgery. Although studies have shown that in many cases the shower is ineffective. Therefore, many clinics began to practice
taking a bath with an antiseptic solution.
At the exit from the sanitary checkpoint, the staff puts on a sterile shirt, pants and shoe covers. After hand treatment, a sterile gown, gauze bandage and sterile gloves are put on in the preoperative room.
The surgeon’s sterile clothing loses its properties after 3-4 hours and is sterilized. Therefore, during complex aseptic operations (such as transplantation), it is advisable to change clothes every 4 hours.
A gauze bandage is an insufficient barrier to pathogenic microflora, and, as studies have shown, about 25% of postoperative purulent complications are caused by a strain of microflora sown both from the festering wound and from the oral cavity of the operating surgeon. The barrier functions of a gauze bandage are improved after treating it with petroleum jelly before sterilization.
Patients themselves may be a potential source of contamination and should be prepared accordingly before surgery.
To reduce the possibility of the spread of microflora throughout the premises of the operating unit, it is advisable to use light bactericidal curtains created in the form of radiation from lamps above doors, in open passages, etc. In this case, the lamps are mounted in metal tube-spots with a narrow slot (0.3 0. 5cm).
Air neutralization with chemicals is carried out in the absence of people. For this purpose, propylene glycol or lactic acid can be used. Propylene glycol is sprayed with a spray bottle at the rate of 1.0 g per 5 m³ of air. Lactic acid used for food purposes is used at the rate of 10 mg per 1 m³ of air. Aseptic air quality in the premises of a surgical hospital and operating unit can also be achieved by using materials that have a bactericidal effect. These substances include phenol and trichlorophenol derivatives, oxydiphenyl, chloramine, formaldehyde and many others. They impregnate bed and underwear, dressing gowns, and dressings. In all cases, the bactericidal properties of the materials last from several weeks to a year. Soft tissues with bactericidal additives retain their bactericidal effect for more than 20 days. It is very effective to apply films or various varnishes and paints to which bactericidal substances are added to the surface of walls and other objects. For example, oxydiphenyl mixed with surfactants is successfully used to impart a residual bactericidal effect to the surface. It should be borne in mind that bactericidal materials do not have a harmful effect on the human body.
In addition to bacterial pollution, air pollution of operating units with narcotic gases: ether, fluorotane is also of great importance. Research shows that during the operation the air in operating rooms contains 400 - 1200 mg/m³ of ether, up to 200 mg/m³ or more of fluorotane, and up to 0.2% carbon dioxide. Very intense air pollution with chemicals is an active factor contributing to the premature onset and development of fatigue in surgeons, as well as the occurrence of unfavorable changes in their health. In order to improve the air environment of operating rooms, in addition to organizing the necessary air exchange, it is necessary to capture and neutralize drug gases entering the air space of the operating room from the anesthesia machine and with exhaled sick air. Activated carbon is used for this. The latter is placed in a glass vessel connected to the valve of the anesthesia machine. The air exhaled by the patient, passing through a layer of coal, is deprived of narcotic residues and comes out purified.
Permissible noise level in surgical hospital premises should not exceed 35 dBA for daytime and 25 dBA for night time, for operating rooms 25 dBA.
Ensuring silence in the premises of the hospital and operating unit should be provided for at the design stages of the hospital: during site allocation, development of a master plan, design of buildings and their construction, as well as during the reconstruction of buildings and structures, and be ensured during operation. Particular attention is paid to protecting the operating unit from various noise influences. In this regard, it should be placed in an isolated extension to the main building with the implementation of noise measures or located on the upper floors of the hospital in a dead-end area. Ventilation devices generate significant noise.
All air supply units should be placed in the basement or ground floor, always under secondary rooms, or in extensions to the main building or in the attic floors. It is advisable to place exhaust chambers and devices in the attic (technical floor), placing them above the auxiliary rooms. The noise from transit air ducts passing through a room can be reduced by lining the inner surface of the air ducts with sound-absorbing material or by increasing the thickness of the walls of the air ducts (if other conditions allow) and applying sound-insulating materials to them.
In order to reduce noise in wards, corridors, halls, pantries and other rooms, sound-absorbing cladding should be used, which must also meet sanitary and hygienic requirements for wet cleaning.
The sanitary-technological equipment of hospitals is also a noise generator. The wheels of gurneys and wheelchairs for patients must have rubber or pneumatic tires, and rubber mats must be placed on carts for tableware. Refrigerators should be installed on special rubber shock absorbers, elevator winches on spring or rubber shock absorbers, elevator doors should be sliding, shaft walls should be double (air gap 56 cm).
Question No. 9. Organization of the work of the purulent dressing room, postoperative ward and surgical department as a whole during planned and unscheduled surgical interventions.
Purulent dressing should be placed in the purulent department next to the purulent operating room. If the block consists of only two operating rooms, then they are divided into clean and purulent. In this case, the purulent operating room should be strictly isolated from the clean one. The following set of “purulent” rooms can be recommended: operating room, preoperative room, sterilization room, anesthesia room, hardware room, room for artificial circulation, auxiliary rooms, staff rooms, airlocks with the necessary equipment.
Number of beds in postoperative wards should be provided according to the norm: two beds per operating room. If there are departments of anesthesiology and intensive care, resuscitation and intensive care, postoperative wards are not provided, and their number is taken into account in the bed capacity of the anesthesiology and intensive care department.
In hospitals where the surgical department is located in a separate building, an emergency department is installed in it, the size and structure of which depend on the capacity of the department. It is highly desirable to have an intensive care unit and an outpatient operating room as part of the emergency department.
Organization of the work of the surgical department.
Planned surgical interventions are performed with the permission of the head of the department, complex cases only after clinical analysis of the patients.
On the morning of the operation, the patient is examined by the operating surgeon and anesthesiologist.
No operation, with the exception of minor interventions (opening the panaritium, treating superficial wounds), should be carried out without the participation of an assistant physician. In the absence of a second surgeon, doctors of other specialties are involved in assisting.
The order and sequence of operations are established, starting with those requiring the most stringent rules of asepsis (on the thyroid gland, for a hernia, etc.). This is followed by operations, after which contamination of the operating room and personnel is possible (on the gastrointestinal tract, for various fistulas).
It is advisable to perform major planned surgical interventions at the beginning of the week. Interventions related to infection in the operating room are scheduled for the end of the week, coinciding with the subsequent general cleaning of the operating room.
The operating nurse is obliged to keep strict records of the instruments, tampons, napkins and other materials taken for the operation, and at the end of the operation, check their availability and report to the surgeon.
Operating rooms and dressing rooms should be subjected to wet cleaning and irradiation with quartz lamps at least twice a day, and general cleaning once a week.
Bacteriological control over the quality of cleaning, the state of microbial contamination of the air (before, during and after the end of the operation) and environmental objects, the sterility of dressing and suture material, instruments and other items should be carried out at least once a month, and the sterility of surgeons’ hands and skin of the surgical field - selectively once a week.
Regulatory basis for the prevention of nosocomial infections
A. E. Fedotov,
Dr. Tech. Sciences, President of ASINCOM
A person's stay in a hospital is dangerous to health.
The reason is nosocomial infections, including those caused by microorganisms that have adapted to traditional hygiene measures and are resistant to antibiotics*.
Eloquent data on this are given in the article by Fabrice Dorchies in this issue of the magazine (page 28). Nobody knows what is going on here. The picture in our hospitals is probably much worse. Judging by the level of current industry regulations, our healthcare has not yet come to an understanding of the problem.
But the problem is clear. It was published in the magazine “Technology of Cleanliness” No. 1/9 10 years ago. In 1998, ASINCOM developed “Standards for Air Cleanliness in Hospitals,” based on foreign experience. In the same year they were sent to the Central Research Institute of Epidemiology. In 2002, this document was submitted to the State Sanitary and Epidemiological Supervision Authority. There was no reaction in both cases.
But in 2003, SanPiN 2.1.3.137503 “Hygienic requirements for the placement, design, equipment and operation of hospitals, maternity hospitals and other medical hospitals” was approved - a backward document, the requirements of which sometimes contradict the laws of physics (see below).
The main objection to the introduction of Western standards is “no money.” It is not true. There is money. But they don't go where they need to go. Ten years of experience in certifying hospital premises by the Clean Room Certification Center and the Clean Room Testing Laboratory have shown that the actual cost of operating rooms and intensive care wards is sometimes several times higher than the costs of facilities built according to European standards and equipped with Western equipment. At the same time, the facilities do not correspond to modern standards.
One of the reasons is the lack of a proper regulatory framework.
Existing standards and norms
Clean room technology has been used in Western hospitals for a long time. Back in 1961, in Great Britain, Professor Sir John Charnley equipped the first “greenhouse” operating room with a downward air flow speed of 0.3 m/s from the ceiling. This was a radical means of reducing the risk of infection in patients undergoing hip joint transplantation. Previously, 9% of patients became infected during surgery and required a second transplant. It was a true tragedy for the patients.
In the 70-80s, cleanliness technology based on ventilation and air conditioning systems and the use of high-efficiency filters became an integral element in hospitals in Europe and America. At the same time, the first standards for air purity in hospitals appeared in Germany, France and Switzerland.
Currently, the second generation of standards based on the current level of knowledge is being released.
Switzerland
In 1987, the Swiss Institute of Health and Hospitals (SKI - Schweizerisches Institut fur Gesundheits- und Krankenhauswesen) adopted the “Guidelines for the construction, operation and maintenance of air treatment systems in hospitals” - SKI, Band 35, “Richtlinien fur Bau, Betrieb und Uberwachung von raumlufttechnischen Anlagen in Spitalern.”
The manual distinguishes three groups of premises:
In 2003, the Swiss Society of Heating and Air-Conditioning Engineers adopted the guideline SWKI 9963 “Heating, ventilation and air-conditioning systems in hospitals (design, construction and operation)”.
Its significant difference is refusal to standardize air cleanliness based on microbial pollution (CFU) to evaluate the performance of the ventilation and air conditioning system.
The evaluation criterion is the concentration of particles in the air (not microorganisms). The manual sets clear requirements for air treatment for operating rooms and provides an original methodology for assessing the effectiveness of cleanliness measures using an aerosol generator.
A detailed analysis of the manual is given in the article by A. Brunner in this issue of the magazine.
Germany
In 1989, Germany adopted the DIN 1946 standard, part 4 “Clean room technology. Clean air systems in hospitals" - DIN 1946, Teil 4. Raumlufttechik. Raumlufttechishe Anlagen in Krankenhausern, Dezember, 1989 (revised 1999).
A draft DIN standard has now been prepared containing purity indicators for both microorganisms (sedimentation method) and particles.
The standard regulates in detail the requirements for hygiene and methods of ensuring cleanliness.
Classes of premises have been established: Ia (highly aseptic operating rooms), Ib (other operating rooms) and II. For classes Ia and Ib, the requirements for the maximum permissible air pollution by microorganisms (sedimentation method) are given:
The requirements for filters for various stages of air purification have been established: F5 (F7) + F9 + H13.
The Society of German Engineers VDI has prepared a draft standard VDI 2167, part: Equipment for hospital buildings - heating, ventilation and air conditioning. The draft is identical to the Swiss manual SWKI 9963 and contains only editorial changes caused by some differences between “Swiss” German and “German” German.
France
The air quality standard AFNOR NFX 906351, 1987 in hospitals was adopted in France in 1987 and revised in 2003.
The standard established maximum permissible concentrations of particles and microorganisms in the air. Particle concentration is determined by two sizes: ≥0.5 µm and ≥5.0 µm.
An important factor is to check cleanliness only in cleanrooms that are equipped. More details on the requirements of the French standard are given in the Fabrice Dorchies article “France: standard for clean air in hospitals” in this issue of the magazine.
The listed standards detail the requirements for operating rooms, establish the number of filtration stages, types of filters, sizes of laminar zones, etc.
Hospital cleanroom design is based on the ISO 14644 series of standards (previously based on Fed. Std. 209D).
Russia
In 2003, SanPiN 2.1.3.1375603 “Hygienic requirements for the placement, design, equipment and operation of hospitals, maternity hospitals and other medical hospitals” was adopted.
A number of requirements in this document are puzzling. For example, Appendix 7 establishes sanitary and microbiological indicators for premises of different cleanliness classes (*equipped state):
In Russia, the cleanliness classes of cleanrooms were established by GOST R 50766695, then GOST R ISO 14644616 2001. In 2002, the latter standard became the CIS standard GOST ISO 146446162002 “Cleanrooms and associated controlled environments, Part 1. Classification of air purity.” It is logical to expect that industry documents should comply with the national standard, not to mention the fact that the definitions of “conditionally clean”, “conditionally dirty” for cleanliness classes, and “dirty ceiling” for ceilings look strange.
SanPiN 2.1.3.1375603 sets for “especially clean” rooms (operating rooms, aseptic boxes for hematological, burn patients) the indicator of the total number of microorganisms in the air (CFU/m 3) before starting work (equipped state) “no more than 200”.
And the French standard NFX 906351 is no more than 5. These patients should be under a unidirectional (laminar) air flow. If there are 200 CFU/m 3 , a patient in a state of immunodeficiency (aseptic box of the hematology department) will inevitably die.
According to Cryocenter LLC (A. N. Gromyko), microbial air pollution in Moscow maternity hospitals ranges from 104 to 105 CFU/m 3, and the last figure refers to the maternity hospital where homeless people are brought.
The air in the Moscow metro contains approximately 700 CFU/m3. This is better than in the “conditionally clean” rooms of hospitals according to SanPiN.
Clause 6.20 of the above SanPiN says: “Air is supplied to sterile rooms using laminar or slightly turbulent jets (air speed less than 0.15 m/s)”.
This contradicts the laws of physics: at a speed of less than 0.2 m/s, the air flow cannot be laminar (unidirectional), and at less than 0.15 m/s it becomes not “weak”, but highly turbulent (non-unidirectional).
The SanPiN numbers are not harmless; they are used to monitor facilities and examine projects by sanitary and epidemiological surveillance authorities. You can release as advanced standards as you like, but as long as SanPiN 2.1.3.1375603 exists, things will not move forward.
It's not just about mistakes. We are talking about the public danger of such documents.
What is the reason for their appearance?
- Ignorance of European norms and basic physics?
- Knowledge, but:
- deliberately worsening conditions in our hospitals?
- lobbying someone's interests (for example, manufacturers of ineffective air purification products)?
How can this be reconciled with the protection of public health and consumer rights?
For us, consumers of healthcare services, this picture is absolutely unacceptable.
Severe and previously incurable diseases were leukemia and other blood diseases.
The patient's bed is in an area of unidirectional air flow (ISO class 5)
Now there is a solution, and the only solution: bone marrow transplantation, then suppression of the body’s immunity for the adaptation period (1-2 months). To prevent a person from dying while in a state of immunodeficiency, he is placed in sterile air conditions (under laminar flow).
This practice has been known around the world for decades. She also came to Russia. In 2005, two intensive care wards for bone marrow transplantation were equipped at the Nizhny Novgorod Regional Children's Clinical Hospital.
The chambers are designed at the level of modern world practice. This is the only means of saving doomed children.
But at the Federal State Institution “Center for Hygiene and Epidemiology of the Nizhny Novgorod Region” they arranged an illiterate and ambitious paperwork delay, delaying the commissioning of the facility for six months. Do these employees understand that unsaved children's lives may be on their conscience? The answer must be given to mothers, looking them in the eyes.
Development of the Russian national standard
Analysis of the experience of foreign colleagues made it possible to identify several key issues, some of which caused heated discussion when discussing the standard.
Room groups
Foreign standards mainly consider operational ones. Some standards address isolators and other premises. There is no comprehensive systematization of premises for all purposes with a focus on ISO cleanliness classification.
The adopted standard introduces five groups of premises depending on the risk of infection of the patient. Separately (group 5) isolation wards and purulent operating rooms are allocated.
The classification of premises is made taking into account risk factors.
Criterion for assessing air purity
What to take as a basis for assessing air cleanliness?:
- particles?
- microorganisms?
- both?
The development of norms in Western countries according to this criterion has its own logic.
At the first stages, the cleanliness of air in hospitals was assessed only by the concentration of microorganisms. Then particle counting began to be used. Back in 1987, the French standard NFX 906351 introduced control of air purity for both particles and microorganisms (see above). Counting particles using a laser particle counter allows you to quickly determine the concentration of particles in real time, while incubating microorganisms on a nutrient medium requires several days.
The next question is: what exactly is checked when certifying clean rooms and ventilation systems?
The quality of their work and the correctness of design solutions are checked. These factors are clearly assessed by the concentration of particles, on which the number of microorganisms depends.
Of course, microbial contamination depends on the cleanliness of walls, equipment, personnel, etc. But these factors relate to current work, to operation, and not to the assessment of engineering systems.
In this regard, Switzerland (SWKI 9963) and Germany (VDI 2167) have taken a logical step forward: they have installed particle-only air monitoring.
The registration of microorganisms remains a function of the hospital epidemiological service and is aimed at ongoing control of cleanliness.
This idea was also included in the draft Russian standard. At this stage, it had to be abandoned due to the categorically negative position of representatives of sanitary and epidemiological supervision.
The maximum permissible standards for particles and microorganisms for various groups of premises are taken according to analogues with Western standards and based on our own experience.
Particle classification corresponds to GOST ISO 1464461.
Cleanroom condition
GOST ISO 1464461 distinguishes three states of cleanrooms.
In the constructed state, compliance with a number of technical requirements is checked. The concentration of pollutants is usually not standardized.
In the equipped state, the room is fully equipped, but there is no staff and the technological process is not carried out (for hospitals - there is no medical staff and no patient).
In the operational state, all processes required by the purpose of the room are carried out in the room.
The rules for the production of medicines - GMP (GOST R 5224962004) provide for the control of contamination by particles both in the equipped state and in the operating state, and by microorganisms - only in the operating state. There is logic to this. Emissions of contaminants from equipment and personnel during the production of medicines can be standardized and compliance with standards can be ensured by technical and organizational measures.
In a medical institution there is an element that is not regulated - the patient. It is impossible to dress him and the medical staff in overalls for ISO class 5 and completely cover the entire surface of the body. Due to the fact that the sources of pollution in the operating state of a hospital premises cannot be controlled, it is pointless to set standards and carry out certification of premises in the operating state, at least in terms of particles.
The developers of all foreign standards understood this. We also included in GOST control of premises only in equipped condition.
Particle sizes
Initially, cleanrooms were controlled for contamination with particles equal to or greater than 0.5 µm (≥0.5 µm). Then, based on specific applications, requirements began to appear for particle concentrations of ≥0.1 µm and ≥0.3 µm (microelectronics), ≥0.5 µm (drug production in addition to particles ≥0.5 µm), etc. .
The analysis showed that it makes no sense for hospitals to follow the “0.5 and 5.0 µm” template, but rather limit themselves to controlling particles ≥0.5 µm.
Unidirectional Flow Speed
Rice. 1. Speed module distribution
It was already noted above that SanPiN 2.1.3.3175603, by setting the maximum permissible speed of unidirectional (laminar) flow of 0.15 m/s, violated the laws of physics.
On the other hand, it is impossible to introduce a GMP standard of 0.45 m/s ±20% in medicine. This will lead to discomfort, superficial dehydration of the wound, may injure it, etc. Therefore, for areas with unidirectional flow (operating rooms, intensive care wards), the speed is set from 0.24 to 0.3 m/s. This is the limit of what is acceptable and cannot be deviated from.
In Fig. Figure 1 shows the distribution of the air flow velocity module in the area of the operating table for a real operating room in one of the hospitals, obtained by computer modeling.
It can be seen that at a low speed of the outgoing flow, it quickly turbulates and does not perform a useful function.
Dimensions of zone with unidirectional air flow
From Fig. 1 shows that the laminar zone with a “blind” plane inside is useless. And in Fig. 2 and 3 show the principle of organizing a unidirectional flow of the operating room of the Central Institute of Traumatology and Orthopedics (CITO). The author underwent surgery for an injury in this operating room six years ago. It is known that a unidirectional air flow narrows at an angle of approximately 15% and what was in CITO does not make sense.
The correct diagram is shown in Fig. 4 (Klimed company).
It is no coincidence that Western standards provide for the size of a ceiling diffuser that creates a unidirectional flow of 3x3 m, without “blind” surfaces inside. Exceptions are allowed for less critical operations.
HVAC Solutions
These solutions meet Western standards, are economical and effective.
Some changes and simplifications have been made without losing the meaning. For example, H14 filters (instead of H13) are used as final filters in operating rooms and intensive care wards, which have the same cost but are significantly more efficient.
Autonomous air purification devices
Autonomous air purifiers are an effective means of ensuring air purity (except for rooms of groups 1 and 2). They are inexpensive, allow flexible decisions and can be used on a mass scale, especially in existing hospitals.
There is a wide variety of air purifiers on the market. Not all of them are effective, some of them are harmful (they produce ozone). The main danger is an unsuccessful choice of air purifier.
The Cleanroom Testing Laboratory conducts experimental evaluation of air purifiers based on their intended purpose. Reliance on reliable results is an important condition for meeting GOST requirements.
Test methods
Guideline SWKI 9963 and draft standard VDI 2167 provide testing procedures for operating rooms using mannequins and aerosol generators (). The use of this technique in Russia is hardly justified.
In a small country, one specialized laboratory can serve all hospitals. For Russia this is unrealistic.
From our point of view, it is not necessary. With the help of mannequins, standard solutions are worked out, which are included in the standard, and then serve as the basis for the design. These standard solutions are tested in the conditions of the institute, which was done in Lucerne (Switzerland).
In mass practice, standard solutions are applied directly. Tests are carried out at the finished facility for compliance with standards and design.
GOST R 5253962006 provides a systematic test program for hospital cleanrooms according to all necessary parameters.
Legionnaires' disease is a companion of old engineering systems
In 1976, an American Legion convention was held in a Philadelphia hotel. Of the 4,000 participants, 200 fell ill and 30 people died. The cause was a species of microorganism called Legionella pneumophila in connection with the mentioned event and numbering more than 40 species. The disease itself was called Legionnaires' disease.
Symptoms of the disease appear 2-10 days after infection in the form of headache, pain in the limbs and throat, accompanied by fever. The course of the disease is similar to ordinary pneumonia, and therefore it is often misdiagnosed as pneumonia.
In Germany, with a population of about 80 million, about 10,000 people suffer from Legionnaires' disease every year, according to official estimates, but most cases remain unsolved.
The infection is transmitted by airborne droplets. The pathogen enters indoor air from old ventilation and air conditioning systems, hot water systems, showers, etc. Legionella multiplies especially quickly in stagnant water at temperatures from 20 to 45 ° C. At 50 °C pasteurization occurs, and at 70 °C disinfection occurs.
Dangerous sources are old large buildings (including hospitals and maternity hospitals) that have ventilation systems and hot water supply.
Means of combating the disease are the use of modern ventilation systems with fairly effective filters and modern water treatment systems, including water circulation, ultraviolet irradiation of water flow, etc.**
* Particularly dangerous are Aspergillus - widespread molds that are usually harmless to humans. But they pose a danger to the health of immunodeficient patients (for example, drug immunosuppression after organ and tissue transplantation or patients with agranulocytosis). For such patients, inhalation of even small doses of Aspergillus spores can cause severe infectious diseases. In first place here is a pulmonary infection (pneumonia). Infections associated with construction or renovation work are common in hospitals. These cases are caused by the release of Aspergillus spores from building materials during construction work, which requires special protective measures to be taken (SWKI 99.3).
** Materials used from the article “Keep Legionella bugs at bay” by M. Hartmann, Cleanroom Technology, March, 2006.
Is it possible to use glycol in installations of supply ventilation systems?
When designing buildings in areas with a design outdoor temperature of –40 °C and below (according to parameters B), it is allowed to use water with additives that prevent it from freezing. Accordingly, the use of an aqueous glycol solution is possible to eliminate the risk of freezing of air heaters.
Are there regulations for MRI rooms?
There are no special rules.
Are there premises in medical buildings with category A for fire and explosion hazard?
The classification of health care facilities by production categories according to ONTP 24-86 is given in PPBO 07-91 “Fire Safety Rules for Health Care Institutions.” In accordance with them, category A includes: premises for storing flammable liquids, storing gas cylinders, paint shops, battery (charging) rooms.
What heating devices are used in the wards of psychiatric hospitals?
Devices with a smooth surface that are resistant to daily exposure to detergents and disinfectants should be used, eliminating the accumulation of dust and microorganisms in all rooms.
How to maintain indoor humidity when using ventilation systems?
For ward rooms during the cold season, you can, for example, use steam humidifiers.
Is it possible to use split systems and fan coils in medical institutions?
Regarding split systems: “the use of split systems is allowed in the presence of high efficiency filters (H11-H14) subject to mandatory compliance with the rules of routine maintenance. Split systems must have a positive sanitary and epidemiological certificate issued in accordance with the established procedure,” that is, a certificate for the possibility of use in medical institutions. We can recommend installing split systems and fan coils in administrative and auxiliary premises. The use of this equipment in medical premises does not provide the required air mobility (0.15–0.2 m/s); in addition, fan coils create background noise that exceeds the permissible values (There are known cases of using fan coils to remove excess heat from equipment in technical rooms KRT.)
Is there a clear requirement for a mandatory certificate for ventilation and air conditioning equipment used in medical institutions?
There are no such requirements in the existing regulatory literature; however, medical equipment must be accepted for installation in healthcare facilities.
How to design ventilation in small built-in or attached dental departments occupying a floor or part of a floor in a building?
It is necessary to provide an independent supply and exhaust ventilation system for the dental department; the influx into the X-ray room can be carried out from a general supply ventilation system with the installation of a check valve; independent exhaust must be provided. Operating rooms require an independent air conditioning system with three stages of supply air purification and the use of a class H filter at the final stage.
Is it possible to serve operating rooms that are part of different departments (“dirty”) and located on different floors with one supply system?
As a rule, these are departments for various technological purposes. The operating room must have cleanliness class A. To avoid the transfer of infection of one type or another between operating rooms through the ventilation system, each operating room (the operating unit of each department) for the case under consideration should be served with an independent supply and exhaust system. If there are several operating rooms in one operating block, they should be combined to be served by one ventilation system.
Do the requirements for operating rooms in clinics need to be the same as the requirements for operating rooms in hospitals?
Yes, you should. The operating room of the clinic is considered as a small operating room, in which the air supply should be carried out through air distributors of slightly turbulent flow.
What filters are used in health care facilities?
To ensure the required class of room cleanliness, it is necessary to provide for the installation of filters and air disinfection devices in ventilation and air conditioning systems.
Ventilation and air conditioning systems for rooms of classes A and B should be equipped with a three-stage system for purification and disinfection of supply air; rooms of other classes may be equipped with a two-stage system.
Air purification filters are used for individual filtration stages. General purpose air filters (coarse and fine filters), as a rule, are used depending on the cleaning stage:
For stage 1 - coarse cleaning group of class not lower than G4 pocket type or F5 (or higher, as an option) depending on the pollution of the outside air;
For stage 2 – fine cleaning group of class not lower than F7;
For stage 3 – high efficiency group of class not lower than H11 and/or air disinfection devices with an efficiency of inactivation of microorganisms and viruses of at least 95%.
When using a filter of class F5 and higher as the 1st stage of cleaning, it is recommended (to extend the service life of the 2nd stage filters) to install an additional pre-cleaning filter of class G3 or G4 in front of the 1st stage filter.
Filters of cleaning stages 1 and 2 are placed directly in the supply ventilation or air conditioning systems:
Stage 1 – at the entrance of outside air to the supply unit to protect the elements of the supply chamber from particles;
Stage 2 – at the outlet of the air handling unit to protect air ducts from particles.
Filters of purification stage 3 are placed as close as possible to the serviced room or in the serviced room itself after the air disinfection device (if necessary).
When choosing an air purification scheme for rooms of cleanliness classes A and B, it is necessary to take into account the indicators of background dust concentrations in the atmospheric air requested from the territorial bodies of Roshydromet. The choice of air purification scheme is carried out in agreement with the territorial bodies of Rospotrebnadzor.
How to humidify the air?
In accordance with the above standards, air humidification should be done with steam (steam generator). Air humidification with water is permissible provided it is disinfected.
The design of air humidification devices and their location must prevent the formation of condensation and drops of moisture after the humidifier and their entry into the supply ventilation system. Air humidification devices of nozzle or film type are installed before the final filtration stage. In case of air humidification with steam, it is recommended to install the steam distribution device directly in the air duct. These devices should be placed in a place accessible for maintenance, cleaning and disinfection.
The steam humidifier is connected to the water supply for replenishment. To ensure reliable operation, it must meet the water quality requirements of the manufacturer.
To reduce the concentration of microorganisms, water should be disinfected.
What air conditioners should be installed in health care facilities?
The equipment of air conditioning (ventilation) systems must be of medical grade.
The question of a special approach to the organization of air conditioning and ventilation systems for “clean” rooms is determined by the very essence of this term.
“Clean” rooms are laboratories in food, pharmaceutical and cosmetic production, in research institutes, experimental rooms, in enterprises for the development and production of microelectronics, etc.
In addition, “clean” rooms include rooms in medical institutions: operating rooms, maternity rooms, intensive care units, anesthesia rooms, and X-ray rooms.
Requirements for a “clean room” and cleanliness class
At the moment, GOST R ISO 14644-1-2000 has been developed and is in force, which is based on the international standard ISO 14644-1-99 “Clean rooms and associated controlled environments”. All companies and organizations responsible for ventilation and air conditioning of such premises must operate in accordance with this document.
The standard describes the requirements for a “clean room” and cleanliness class - from 1 ISO (highest class) to 9 ISO (lowest class). The cleanliness class is determined depending on the permissible concentration of suspended particles in the air and their size. For example, the cleanliness class of operating rooms is 5 and higher. To determine the cleanliness class, the number of microorganisms in the air is also counted. For example, in class 1 premises there should be no microorganisms at all.
A “clean” room must be designed and equipped in such a way as to minimize the entry of suspended particles into the room, and if they do, isolate them inside and limit their release to the outside. In addition, the specified temperature, humidity and pressure must be constantly and continuously maintained in these rooms.
Features of ventilation and air conditioning for “clean” rooms
Based on the foregoing, the following features of ventilation and air conditioning systems are distinguished:
- In “clean” and medical premises, the installation of air conditioners with recirculation air, only supply type, is prohibited. Installation of split systems is allowed in the administrative premises of health care facilities and laboratories.
- To ensure and maintain precise temperature and humidity parameters, precision air conditioners are often used.
- The design and material of air ducts, filter chambers and their elements must be adapted for regular cleaning and disinfection.
- A multi-stage filtration system (at least two filters) must be installed in the air conditioning and ventilation network and HEPA (High Efficiency Particular Airfilters) final filters must be used.
Air filters vary depending on the cleaning stages: 1st stage (coarse cleaning) 4-5; 2 stages (fine cleaning) from F7 and higher; 3 stages - high efficiency filters above H11. Accordingly, first-stage filters take in outside air - they are installed at the air inlet into the air supply unit and protect the supply chamber from particles. Second stage filters are installed at the outlet of the supply plenum and protect the air duct from particles. Third stage filters are installed in close proximity to the premises being served.
- Providing air exchange - creating excess pressure in relation to neighboring rooms.
The main tasks of the ventilation and air conditioning system for clean rooms: removal of exhaust air from the premises; provision of supply air, its distribution and volume regulation; preparation of supply air according to specified parameters - humidity, temperature, cleaning; organizing the direction of air movement based on the characteristics of the premises.
In addition to the air preparation and distribution system, the design of a “clean” room requires a whole range of additional elements: enclosing structures - hygienic wall barriers, doors, sealed ceilings, antistatic floors; control and dispatch system for supply and exhaust systems; a number of other special engineering equipment.
The design and installation of air preparation and distribution systems should only be carried out by specialized companies that have experience in such work, comply with all GOSTs and requirements, and provide an integrated approach to the organization of “clean” rooms. One contractor should ideally carry out design and construction work, assembly and installation, commissioning and training of personnel in the specifics of being in the premises.
How to choose a contractor
To choose a contractor, you need:
- find out if the company has experience in implementing GMP standards (Good Manufacturing Practice - a system of rules and regulations governing the production of medicines, food, food additives, etc.) or ISO 9000 standards;
- get acquainted with the company’s experience and portfolio of projects for the organization of “clean” rooms that it has carried out;
- request existing distribution certificates, certificates of compliance with GOSTs, SRO approvals for design and installation work, licenses, technical regulations, cleanliness protocols and work permits;
- meet the team of specialists involved in design and installation;
- Find out the conditions of warranty and post-warranty service.
