Biological safety cabinets: 3 classes
The aim of biological safety cabinets is protection the staff, products and the surrounding from substances and potentially hazardous microbes.
According to their construction, they are ventilated enclosure having continuous airflow. HEPA filters discharge such flows to the atmosphere.
Class I biosafety cabinets give both environmental and personal protection, but there is no protection of products. They are needed in cases of low and medium risks of biological objects.
Comparing with chemical fume hoods, they have also turbulent flow inside, but also HEPA filter is available, at the part of exhaust system. This type is considered to be not so modern, as classes II and III.
Class II biosafety cabinets give not only environmental and personal protection, but also provide product protection. These devices are very popular in the spheres of medicine, in biological and also microbiological labs. In such case the downward laminar flow of air provides protection for specimens being investigated in such cabinets. HEPA filters can work with recirculation or going away from lab (A Type or B Type, respectively), providing the effective environmental protection.
Class III cabinets provide protection from extremely risky biological agents and infections, their protection level is the highest. That is why this type costs more than previous ones.