There are several kinds of safety cabinets available, in many laboratories there are so-called Tissue culture cabinets and Biological safety cabinets. All of these cabinets are commonly referred to as safety cabinets or "laminar flow" cabinets. They all pump air through a HEPA filter (High efficiency particulate air filter), in a slow layered flow, ie. flow without turbulence or currents. Hence the name laminar flow cabinets.
Clean benches are designed to pump air through a HEPA filter horizontally out of the cabinet towards the user. Hence, these cabinets are selected for work with samples or cultures that are sensitive to pollution because the subject inside the cabinet is protected for the user and the environment. The user, on the other hand, is not protected against unwanted effects from the culture or sample. These cabinets are therefore, strictly speaking, not safety cabinets.
Biosafety cabinets are available in three categories with different properties. When planning work, make sure that the cabinet to be used is of a suitable category.
Category I are cabinets that protect the user and the environment and not the subject. The air is taken in through the front opening of the cabinet and in fact the suction into the cabinet can cause pollution in samples and cultures. The function of these cabinets is similar to ordinary suction cabinets except that the air is filtered through a HEPA filter before it is blown out. Cabinets of this type are not suitable for work with samples or cultures that are sensitive to pollution
Category II are cabinets where the user, the environment and the subject are protected against each other. Air is pumped into these cabinets through a HEPA filter before it passes through the work space and then back through a HEPA filter as it exits the cabinet. These cabinets are divided into two subcategories, A and B, depending on how airflow is directed through them. The most common safety cabinets are Class A-II cabinets.
Category III are highly specialized cabinets that are completely closed and used for work with dangerous pathogens and substances. These cabinets are rare, usually custom-made, and only available in select, specially designed laboratories.
- Turn off the UV light when working in the cabinet. Note: Ultraviolet light alone is not 100% safe for disinfecting cabinets. Other methods must be applied as well.
- Turn on the light and make sure that nothing obstructs the flow of air through the perforated sieve at the front, that is where air is pumped into the cabinet.
- Keep the cabinet closed, turn on the fan and allow it to work for approx. 5 minutes to clean the air inside the cabinet.
- While the cabinet is cleaning itself, you have time to wash your hands thoroughly.
- Wear a labcoat and gloves.
- Disinfect the cabinet with disinfectant, e.g. 70% Ethanol. Start at the bottom and swipe from right to left across the field, towards you. Also stroke the ceiling and sides and the inside of the glass door.
- Put the things you need to work in the cabinet (trash can, pipette tips, etc.). Arrange them so that you can minimize your movements inside the cabinet
- Define a clean area and waste area as each should be adjacent to your work area.
- When you put your hands in the cabinet to start working, pause for a moment to allow the cabinet's airflow to adjust.
- Keep hand movements inside the cabinet to a minimum. All movements should be slow and preferably in and out of the closet but as little as possible to the sides. Remember that the safety of the cabinet is all based on how air flows through it.
- When the work is finished, remove all waste from the cabinet and disinfect it as appropriate.
- Wipe and disinfect the work area as before. Close the cabinet, switch off the light and allow the fan to run for approximately 5 minutes before switching it off.
- Turn on the ultraviolet light and let it stay on for 30 minutes. There is no reason to leave it on for longer, it shortens the lifetime of the UV-lighbulb, but after 30 minutes the ultraviolet light has done its work .