1. Requirements for clean air conditioning technology in SPF laboratory animal environment
According to the National Standard for Laboratory Animal Environment and Facilities promulgated in 1994, the experimental animal environment is mainly divided into open system, sub-barrier system, barrier system and isolation system. The open system is suitable for feeding common-grade experimental animals. The sub-barrier system is suitable for feeding clean-grade experimental animals. The barrier system is suitable for feeding experimental animals without specific pathogens (SPF). The isolation system is suitable for raising SPF and sterile (GF) grades. Experimental animals. At present, the newly built experimental animal room is mainly SPF grade. According to the standard, the air purification degree should reach at least 10000 grade, ammonia concentration ≤14mg/m3, temperature 18～29°C, daily temperature difference ≤3°C, relative humidity 40～70%. , air flow speed ≤ 0.18m / s, room air pressure difference gradient 20 ~ 50Pa.
In order to ensure the normal growth of experimental animals, it is necessary to strictly adjust the temperature and humidity according to the regulations to provide fresh air to eliminate harmful gases, pathogenic microorganisms and dust particles. In order to avoid cross-infection, the air pressure in each part of the room must be strictly set and controlled. Therefore, the establishment of SPF experimental animal environment must have a clean air conditioning system with reasonable design, reliable operation, energy saving and convenient monitoring.
2. Status and problems of environmental purification air conditioning technology for SPF experimental animals
Although the SPF laboratory animal environment does not require high air cleanliness, there are special requirements for ventilation. First, it is necessary to provide the fresh clean air required for the normal life of the experimental animals, to exclude the polluting gases emitted from the animal excrement, and to prevent cross-contamination of the air. In order to achieve this goal, most of the domestic SPF experimental animal environment adopts the straight-line new air purification method. The clean air of constant temperature and humidity is sent to the SPF laboratory animal room to dilute the polluted air and will not be directly discharged. The commonly used airflow form is the top-feeding side return. The clean air is sent by the high-efficiency air supply port at the top of the room. The experimental animal cage is placed in the room, and the clean air dilutes the indoor polluted air and then follows the air outlet of the lower part of the room. discharge. The method of purifying and blowing air is simple in principle, convenient in management, and has obtained many applications. However, this kind of air supply method has a large air volume, high energy consumption, and is not reasonable in use, because not all dust particles are pathogenic microorganisms, and it is not necessarily possible to dilute the polluted air in the room by relying on a large amount of clean airflow. Get a good living environment. At present, the general SPF experimental animal house is raised in the breeding box (cage), the feeding box (cage) is placed on the multi-layer cage, and many rows of cages can be placed indoors. The feeding box (cage) is the micro-environment of the living animals of the experimental animals, and is the core of dust particles and odors, and also the dead angle of air flow. The whole room is a large environment of air circulation, and the airflow is distributed in a turbulent flow. Due to the resistance of the feeding box (cage) and the cage, only a small part of the clean air can enter the feeding box (cage), and most of the constant temperature and humidity clean air Directly discharged from the exhaust vent, causing a great waste of energy. Even if the polluted air emitted or replaced from the feeding box (cage) cannot be completely discharged to the outside immediately, the polluted air will permeate the entire room with the turbulent airflow, which not only causes the possibility of cross-contamination of the experimental animals, but also makes The working environment of the breeder has deteriorated. The volume of the common feeding box (cage) is only 10% of the space of the house. Due to the resistance of the feeding box (cage) and the cage, the clean air that can directly participate in the air exchange in the feeding box (cage) will be less than 10%. To ensure a certain temperature, humidity, cleanliness and air freshness in the feeding box (cage), it is necessary to double the air conditioning unit, increase the air supply volume, increase the cooling and heating power, which increases the construction investment. And running costs. Most of this energy is wasted and wasted, which is the main problem of the straight-line new wind purification method.
3. Application of clean air conditioning energy saving technology in SPF experimental animal environment
With the promotion and implementation of the SPF experimental animal environment, the problem of high energy consumption and high investment and operating costs has become more and more prominent. Scholars at home and abroad have done a lot of research and exploration in this area. The experience is as follows:
3.1 Reduce the heat and cold load
3.1.1 Reducing the indoor height The height of the general biological clean room is between 2.4 and 2.6m. The SPF laboratory animal has fewer environmental workers and short working hours. In order to reduce the clean air unit flow, the room height can be reduced to 2m.
3.1.2 Strengthening the insulation and insulation
Choose a good insulation material and thicken the insulation layer.
3.1.3 Regulating airflow speed
The variable frequency speed control automatic control technology is adopted to control the air flow speed to the standard lower limit, and the minimum air flow rate can be selected to be 0.1 m/s.
3.1.4 Control temperature range
Set the temperature of the SPF experimental animal room to the standard lower limit in winter and set it to the standard upper limit in summer.
3.1.5 Small unit independent air conditioning system
The SPF experimental animal house is divided into several areas, and a number of small unit independent air conditioning systems are set up accordingly. When using, according to the increase and decrease of the animal breeding type and quantity, the room and the corresponding air conditioning system are selectively activated to avoid the air conditioning system running out.
3.2 Secondary use of energy
3.2.1 Purifying air recycling
The partially exhausted purified air-conditioning air is recycled and used, and must be pre-treated before being recycled to remove dust particles and harmful gases in the secondary circulating air. The secondary cycle air recovery rate can be up to 50%. However, to avoid cross-infection, recirculated air is limited to the same (animal population) unit.
3.2.2 Energy recovery
Install an energy recovery device in the exhaust duct section. The above measures using secondary energy are both theoretically and technically feasible, especially in areas with large temperature differences. However, in order to deal with the return air, it is necessary to increase the corresponding device, and increase the air system resistance and operating cost, so the energy saving effect is not very significant under normal circumstances.
3.3 Using natural energy
Use natural resources such as solar energy for air conditioning or auxiliary heating where conditions permit.
3.4 Air Directional Flow Technology
With the construction of the SPF experimental animal environment, the contradiction between energy consumption and high operating cost has become more and more prominent, and an air-directed flow technology has received more and more attention. As mentioned above, in the general SPF laboratory animal room, only less than 10% of the clean air participates in the exchange of air in the animal feeding box (cage). Therefore, in order to achieve energy saving, it is necessary to minimize the non-exchange purifying airflow and let The exchangeable gas flows in a directional direction and finally enters the exhaust duct. According to this principle, a variety of air-directed flow SPF experimental animal environmental technologies have been applied.
3.4.1 In-box exchange cage
The technology adopts the air guiding channel cage, the double air duct unit, the front end and the terminal air filter are arranged to form a single air exchange system, and the purified air flow is directed in the animal feeding box, all participating in the air exchange in the box, the air The traffic is very small. The device simplifies the control equipment, is convenient and flexible to use, and has low requirements on the basic building, and is particularly suitable for feeding small-scale experimental animals. At present, there are a series of complete sets of equipment available for selection in China.
3.4.2 Directional flow SPF experimental animal room
The technology uses the high-efficiency air supply opening at the top of the room to send clean air into the room. The animal cage is divided into several relatively closed cages. The cage can be placed in the animal feeding box (cage). Each cage has ventilation holes and cleanliness. The chamber is connected to the exhaust vent. After the clean air enters the room from the top of the room, the air can only enter the cage from the vent and enter the exhaust duct to form a directional flow. According to the SPF experimental animal room directional flow technology and the traditional in-line airflow technology in the feeding area air volume and cold (heat) load parameters, the former can save 62% of energy, the investment and operating costs are greatly reduced.
3.4.3 Application of clean space and transfer technology in SPF experimental animal environment
Freeing from the traditional barrier system, reducing fixed plant and large-scale investment, saving energy is the goal that people have been exploring. In the ordinary temperature-controlled building, France's Lakalin Company used the isolation technology and transmission device to establish a SPF experimental animal environment device with adjustable size. The purified air is directed and flowed in the isolator, and all participate in the exchange of airflow in the living space of the animal. The operating space and the flow of people are completely separated. At present, a double lifting isolator can hold 98 small mouse boxes. The largest isolator can be used to raise horses. The door-type direct transmission device is mainly used during operation. The staff is free to enter and exit, and the operation is convenient. The system is simple and flexible, the flow of people is absolutely isolated, the operation is safe and reliable, and the scope of adaptation is wide. It is a good way to facilitate energy saving insurance. Practice has proved that the above-mentioned air-conditioning energy-saving technology is effective in improving the air quality and energy-saving level of the SPF experimental animal environment. In particular, the air directional flow technology solves the problem of waste energy and cross-contamination of non-exchange purifying airflow theoretically and technically, and has the advantages of saving investment and reducing operating cost, and is the development direction of SPF experimental animal environmental engineering purification air-conditioning energy-saving technology.
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