With the rapid development of China’s biological, medical and health undertakings, more and more biosafety laboratories have been established in various fields such as microbiology research, biotechnology development, genetic genetic engineering, special medical surgical wards, and anti-terrorism for biochemical weapons. After being put into use, especially after SARS, it will develop faster. Biosafety laboratory design requirements for ventilation and air conditioning systems are different from common biological cleanrooms in many aspects, such as system partitioning, equipment backup, airflow direction, pressure control, air supply and exhaust treatment, and system control.
According to the degree of bio-risk of the objects handled by the laboratory and the protective measures taken, biosafety laboratories are divided into four levels, of which the first level has the lowest requirement for bio-safety isolation and the fourth highest, ie commonly known as P1, P2, P3, P4. laboratory. Generally, the corresponding level of biosafety laboratories is denoted by BSL-1 to 4; the corresponding level of animal biosafety laboratories is represented by ABSL-1 to 4. Since P1 and P2 do not have very special requirements for ventilation and air conditioning systems, this paper mainly discusses the design requirements of P3 and P4 laboratories for ventilation and air conditioning systems.
1 air conditioning system form
The division of air-conditioning purification systems in biosafety laboratories shall be determined after technical and economic comparisons based on the hazard level of the operation object, the layout of the plane, etc. Effective measures shall be taken to avoid contamination and cross-contamination. The division of the air-conditioning purification system should be conducive to the automatic control system settings and energy-saving operation.
Secondary biosafety laboratories can use air-conditioning systems with recirculating air. If chemical solvents, infectious material handling and animal experiments are involved, a full exhaust system should be used. The third-level and fourth-level biosafety laboratories should adopt an all-new air system, and the air-supply and exhaust air mains should be equipped with airtight valves. Normal fan coil units or room air conditioners must not be installed in contaminated and semi-polluted areas. Animal biosafety laboratories should meet the relevant requirements of GB 14925 "Environment and Facilities for Laboratory Animals" at the same time.
The exhaust air of the third and fourth level biosafety laboratories must be filtered and discharged through a high-efficiency filter. The efficiency of high-efficiency filters is not lower than that of Class B. The exhaust high efficiency filter should be located at the indoor exhaust outlet. In addition to the first high-efficiency filter at the indoor vent, the fourth-grade biosafety laboratory must also be followed by a second high-efficiency filter. The distance between the two high-efficiency filters should not be less than 500mm. If necessary, a high temperature air sterilizer can be used instead of the second high efficiency filter.
The location of the first high efficiency filter for exhaust ventilation shall not be deep inside the pipe or clip wall and shall be adjacent to the exhaust outlet. The position of the filter and the vent should be easy to replace the filter safely. The positive pressure section of the exhaust duct should not cross the room, and the exhaust fan should be located near the outdoor exhaust vent. The exhaust fan unit must be used one by one. Exhaust volume must be calculated and calculated in detail. The total amount of exhaust air should include the amount of air leakage from the envelope structure, biological safety cabinets, and the amount of exhaust air from equipment such as centrifuges and vacuum pumps.
The installation of the three- and four-level biosafety laboratory exhaust high-efficiency filters should have the conditions for on-site leak detection. If the site does not have the conditions for leak detection, a dedicated high-efficiency filtering device for exhaust air should be used. Vented airtight valves should be located between the exhaust high efficiency filter and the exhaust fan. Outside the exhaust fan exhaust pipe should be installed on the protective net and rain cover.
4 Air flow organization
The location of various equipment within the main biosafety laboratory should facilitate the flow of air from the “clean” space to the “contaminated” space, minimizing the return flow and turbulence in the room. The direction of the air flow between the districts in the biosafety laboratory should ensure that the flow from the clean area to the semi-polluted area and from the semi-polluted area to the contaminated area. A positive pressure buffer chamber should be set up in the clean area of the Biosafety Laboratory.
The airflow organization should adopt the upper-lower delivery method, and the arrangement of the air supply and exhaust outlets should minimize the stagnant space in the indoor air flow. No air outlets should be provided near the biological safety cabinet operating surface or other aerosol-operated locations. The outlet of the HEPA filter should be located in the indoor area where the risk of contamination is highest, and it should be arranged unilaterally without any obstacles. The lower edge of the high-efficiency filter exhaust outlet shall not be less than 0.1m above the ground and shall not exceed 0.15m; the height of the upper edge shall not exceed 0.6m above the ground. Exhaust outlet speed should generally not exceed 1m/s.
5 Electrical and Automation Systems
Electrical and automation systems are the guarantee for reliable and energy-efficient operation of ventilation and air conditioning systems. The automatic control system must ensure differential pressure requirements in each area. Air supply and exhaust systems must be linked reliably to ensure stable pressure gradients. When the exhaust fan group fails, the spare exhaust fan group should be able to automatically put into operation. At the same time, an alarm signal should be issued and maintenance should be carried out immediately. Air-conditioning ventilation equipment should be able to automatically and manually control, and control and display panels should be located in the clean area. At the same time, in order to save energy, it is recommended that ventilation and air conditioning systems be designed according to variable air volume systems to reduce operating costs as much as possible.
Researchers in P3 and P4 laboratories are all pathogenic microorganisms that are highly harmful to individuals and the environment. It has been reported when pathogens escaped from biosafety laboratories and the quality of ventilation and air conditioning systems directly affects the safety of laboratories. Sex. Therefore, the ventilation and air-conditioning system must be carefully designed to take reliable measures to prevent pathogenic microorganisms from contaminating the indoor and outdoor environments, while protecting the subjects from being contaminated and ensuring the smooth progress of experiments and production.