Laboratory centrifuge safety protection: prevent aerosol diffusion and inhalation

Centrifuge is one of the most commonly used tools in the laboratory. The laboratory has a large workload. Every day, it is responsible for the examination of various clinical specimens such as blood, body fluids, secretions and excretions. The blood samples in these specimens are the largest. And the blood specimens need to be centrifuged, the serum can be separated for testing, and many other specimens need to be centrifuged. The utilization rate of the centrifuge is very large. Therefore, the disinfection of the centrifuge and the aerosol prevention and control of the laboratory are very important.

Contamination of the centrifuge During the centrifugation of the specimen, if the test tube cap is not tightly closed or there is no test tube cap, carelessness during placement or removal, as well as unbalanced placement, damage to the test tube, etc., may cause the specimen to overflow and cause the centrifuge to become contaminated. Centrifuges also produce aerosols during high-speed operation. These specimens are specimens of different types of patients and contain pathogenic microorganisms and biomolecules that are harmful to the environment and human health. The aerosol generated by the dust or dirt in the centrifuge during the high-speed operation will also cause great damage to the human respiratory system, digestive system, nervous system and the like.

Regardless of the type of microbiology laboratory, aerosol production is inevitable as long as the infectious substance is handled. Therefore, in addition to controlling airborne infections, it is also necessary to prevent the spread of aerosols, which is the second step in controlling airborne infections. In the laboratory, there are a variety of measures to effectively prevent the spread of aerosols, such as “enclosure operations”, “barrier separation”, “effective interception”, “directional airflow”, “air disinfection”, etc. Use can get good results.

(1) Paddock operation: The paddock operation is to restrict the infectious material to a space as small as possible (such as a biological safety cabinet) so that it does not directly contact the human body and is isolated from the open air to avoid human exposure. . The laboratory is also a paddock, and it is the second line of defense, which can play a "double protection" role. The size of the paddock should be appropriate to achieve the goal of ensuring safety and economy. At present, the facilities and equipment for the operation of the paddock are often combined with various protection principles such as mechanical, air curtain and negative pressure.

(2) Barrier isolation: Once the aerosol is generated and breaks through the paddock, it must be prevented by various barriers, so it can also be regarded as the second layer of paddock. For example, biosafety laboratory enclosures and their buffer chambers or passages prevent aerosols from spreading further, protecting the environment and public health. For example, the buffer between the core area of ​​the BSL-3 laboratory and the semi-contaminated area places the core area of ​​the infective material as small as possible. According to the requirements of the national standard "General Requirements for Laboratory Biosafety" (GBl9489-2004), the buffer room entering and leaving the core laboratory is a necessary setting. This is because:

1) Avoid the spread of pollution and limit the pollution to a minimum as far as possible;

2) Once there is positive pressure in the room, the staff can ventilate, purify the air and evacuate safely in the buffer room;

3) When you withdraw from the laboratory, you can change shoes, remove outer clothes and gloves, and disinfect necessaryly to avoid internal

Layers of clothing contaminate or contaminate other rooms.

(3) Directional airflow: The requirement for a biosafety level three or higher laboratory is to maintain a directional airflow. Its requirements include:

1) The air around the laboratory should flow into the laboratory to prevent the spread of polluted air and ensure that it does not endanger the public;

2) Inside the laboratory, the air in the clean area should flow to the operating area to ensure no backflow to reduce the exposure of workers;

3) The air in the lightly polluted area should flow to the heavily polluted area.

Taking BSL-3 laboratory as an example, in principle, the semi-polluted area should be 20Pa compared with the outside air pressure, and the core laboratory pressure should be 20Pa compared with the semi-polluted area. The air pressure in the infected animal room and the dissection room should be low. In the core area of ​​the ordinary BSL-3 laboratory.

(4) Effective disinfection and sterilization: The application of disinfection technology is indispensable in all aspects of laboratory biosafety. The disinfection of the laboratory mainly includes disinfection and sterilization of air, surface, instruments, waste, and waste water. In the application, attention should be paid to the targeted selection based on the characteristics of the biological factors and the disinfecting objects. And should pay attention to the impact of environmental conditions on the disinfection effect. All of these should be specified in the operating procedures.

(5) Effective interception: It means that the air in the biosafety laboratory must be filtered by a high-efficiency particle air (HEPA) filter before the air is discharged into the atmosphere, and the infectious particles are blocked on the filter. This method is simple, effective, and economical. The filter material of the HEPA filter is multi-layered and grid-staggered, so the principle of intercepting infectious aerosol particles is:

1) sieving: particles smaller than the mesh of the filter material may pass, and larger than the intercepted;

2) Settlement: Stronger for aerosol particles with a diameter of 0.3/zm or more. Although the diameter of the aerosol particles is smaller than the mesh, it may be blocked on the filter due to the gravity and thermal settling or electrostatic deposition of the particles;

3) Inertial impact: Although the aerosol particle diameter is smaller than the mesh, it may block on the filter material due to the inertial impact of the particles;

4) Particle diffusion: for diameters less than o. The 1Um aerosol particles act strongly, and although the aerosol particles are smaller than the mesh, they may be blocked on the filter due to the diffusion of the particles.

According to the above principle, the particles which are least likely to be filtered out are particles of 0.1 to 0.3/zm.

Prevent aerosol inhalation

The laboratory should choose a sealed centrifuge with safety, good performance, standard certification, safety measures such as automatic rotor identification and lock operation to ensure safety. Strengthening the training and assessment of biosafety of laboratory staff, especially the pollution of centrifuge aerosols, should be paid attention to by staff. To standardize the operation of the laboratory centrifuge , the test tube must be tightly closed and placed to prevent the specimen from overflowing. During centrifugation, the operator should not face the centrifuge too close. After the centrifuge stops, turn on the centrifuge cover 2~3 minutes to reduce the harm of aerosol to the staff. If necessary, wear a mask to operate the centrifuge. The surface of the centrifuge should be cleaned and disinfected daily, and it should be wiped regularly. If the centrifuge tube is not closed or the test tube is broken during use, the liquid overflows to contaminate the centrifuge, and the inside of the centrifuge should be disinfected immediately.

Despite the above measures to prevent the spread of aerosols, the aerosols inevitably contaminate the laboratory air due to their strong diffusion capacity. Therefore, laboratory staff still need personal protection to prevent aerosols from inhaling.