Selection of positive pressure protective clothing during the design and construction of biological laboratories

Selection of positive pressure protective clothing during the design and construction of biological laboratories

Overview of Positive Pressure Protective Clothing

Positive pressure protective clothing refers to clothing that completely seals the human body, is used to prevent special biological factors from harming the human body, and the internal pressure is not lower than the environmental pressure under normal working conditions. It is mainly used for positive pressure clothing type biosafety level 4 laboratory. host...

Text label: biological laboratory design, biological laboratory construction, selection of positive pressure protective clothing

Type selection of positive pressure protective clothing in the design and construction of biological pharma machinery

Overview of Positive Pressure Protective Clothing

Positive pressure protective clothing refers to clothing that completely seals the human body, is used to prevent special biological factors from harming the human body, and the internal pressure is not lower than the environmental pressure under normal working conditions. It is mainly used for positive pressure clothing type biosafety level 4 laboratory. The main feature is that the gas pressure in the protective clothing is higher than the gas pressure of the environment, so as to isolate the hazards caused by the exposure of the experimental personnel to aerosols, radioactive dust, splashes, and accidental contact in the contaminated area. At present, several biosafety level 4 laboratories have been built in my country, all of which use positive pressure protective clothing as the preferred personal protective equipment.

Problems that should be paid attention to in design and construction:

For positive pressure protective clothing, the key issues that should be considered during the design and construction stage of the biosafety laboratory include: the selection of positive pressure protective clothing (involving the pressure and flow of the required air supply when it is in normal working condition) , the amount of exhaust air to the room, etc.), quantity requirements, etc. The selection of positive pressure protective clothing should consider the corrosion resistance of its own material, air tightness, and the size of the person to be worn, and the number should meet the actual work needs of the laboratory. The selection and quantity of positive pressure protective clothing are important parameters for the air supply capacity of the life support system and the design of the ventilation and air conditioning automatic control system. When designing the ventilation system and automatic control system of the biosafety laboratory, the influence of the positive pressure protective clothing exhaust on the indoor pressure gradient should be considered, and automatic control and adjustment measures should be taken.

When operators wear positive pressure protective clothing to enter or leave a functional room of the laboratory (mainly including positive pressure protective clothing changing room, chemical shower room, main laboratory, and some also include protective corridors, main laboratory buffer room, etc.) , because the positive pressure protective clothing exhausts the air indoors (each set of exhaust air volume is about 20~100m3/h), it will reduce the absolute negative pressure value of the laboratory room with better air tightness (such as from -80Pa to -60Pa) , so that the relative pressure difference between the adjacent rooms in the outdoor direction does not meet the standard requirements, and even the pressure difference is reversed. At this time, it should be adjusted by the pressure control method.

1. Tracking dynamic control

For high-level biosafety laboratories that use 'fixed transmission and variable dischargeIn the high-level biosafety pharma machinery of 'rowIn the past, some experts have raised the issue of whether the air volume control valve can adapt to precise pressure control due to the large volume of air supply and exhaust in large rooms (such as the main laboratory, protective corridor, etc.). This problem can be solved by connecting the mother and child air ducts in parallel, that is, the mother air duct adopts a constant flow method to pass a large air volume, and the air duct adopts a variable flow method to pass a small air volume, which can realize accurate air volume adjustment and pressure control in the laboratory. Zhongjing Global Purification can provide consulting, planning, design, construction, installation and transformation of sterile rooms and biological laboratories and other supporting services.

2. Initial static control

In order to solve the problem of the reduction of absolute pressure difference caused by the positive pressure protective clothing exhausting air to the room, the reduction of relative pressure difference with the adjacent rooms in the outdoor direction, or even the reversal of pressure difference, in addition to the pressure control adjustment, It can also be solved through the initial static control idea, that is, the main laboratory supply and exhaust pipes are equipped with manual adjustment valves (or constant air volume valves), and the air volume adjustment is not carried out through the air volume adjustment valve during the entire laboratory operation process, only through the initial setting. A large static pressure difference solves the problem of positive pressure protective clothing exhausting air into the room, such as the initial static pressure difference between a BSL-4 main laboratory and the adjacent buffer room 'General Requirements for Biosafety' GB19489--2008 and ' Biosafety Building Technical Specifications GB

50346-2011 requires -25Pa, set it to -50Pa when debugging. When the operator wears positive pressure protective clothing and enters the main laboratory, the static pressure difference between the main laboratory and the adjacent buffer is reduced to -30Pa, which can still meet the standard requirements. If it does not meet the standard requirements, it indicates the initial static pressure difference. -50Pa is still not enough to offset the effect of positive pressure protective clothing exhaust, and the initial static pressure difference should be further increased until the requirements are met.

After the installation of the ventilation and air-conditioning system is completed, the initial air balance adjustment of the manual regulating valve can be carried out. In the actual operation process, there is basically no adjustment and control of the air volume regulating valve, which greatly simplifies the automatic control system. Relying on the static pressure difference with large initial value to reduce the influence of indoor pressure disturbance factors still has certain limitations. If a larger static pressure difference is required, the negative pressure of the main laboratory will be too large in the initial state. At this time, the pressure control method needs to be used for adjustment and control, that is, the room with strong pressure disturbance needs to be set with an air volume control valve for air volume control.

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