In order to maximize productivity while maintaining the highest level of safety, biosafety cabinets have become a crucial component.

From the earliest laboratory-acquired typhoid infections, to the hazards posed by today’s antibiotic-resistant bacteria and rapidly mutating viruses, threats to worker safety have stimulated the development of refined cabinets in which infectious agents or chemical carcinogens can be handled safely. Research demands are pushing laboratories to their maximum capacity. As such, eliminating the risk of contamination to both users and samples has become of paramount importance. Working with animal tissues and cell cultures, maintaining sterility of cell lines, along with efforts to minimize crosscontamination, contribute to these concerns. As a result, there is an increased need for biological safety cabinets (BSCs) to provide maximum sample protection and user safety. In order to maximize the laboratory productivity while maintaining the highest level of safety, these cabinets have become a crucial component within the laboratory.

CONTAMINATION CONTROL
Contamination is a major issue associated with all experimental procedures. Contaminating microorganisms can be detrimental to important experimental data, furthermore, as the air is circulated, there is always the possibility of the user inhaling contaminants carried in it. It is also essential to prevent contamination of the air exhausted out of the building which can have potentially harmful effects on the environment. Product design, airflow optimization, and improved filters all have a major impact on improving the performance of safe containment.

HEPA filters
Early prototype clean air cabinets were designed to protect important samples from contamination, rather than to protect the worker from the risks associated with the manipulation of the materials. Air was filtered and blown directly across the work surface, towards the user. Therefore, these early prototypes could not be used for handling any infectious agents as the user would be directly in a stream of contaminated air. To protect the worker during the manipulation of infectious agents, the biological safety cabinet was developed, but a mechanism to filter out environmental microorganisms and other undesirable particulate matter from the exhausted air was required.

Control of airborne particles became possible with the development of high efficiency particulate air (HEPA) filters which can effectively remove microscopic contaminants from the air. HEPA filters are generally rated as being at least 99.97% effective at removing 0.3µm-sized particles and even more effective at removing larger and smaller particles. A typical HEPA filter is made of a single sheet of borosilicate fibers treated with a wet-strength water-repellent binder. The filter medium is pleated to increase the surface area, and may be divided by corrugated separators. Careless handling of the filter can damage the medium, resulting in leaks and reducing its efficiency. For this reason, filter integrity must be certified after a BSC is initially installed and after it has been relocated.

HEPA filters work on the basis of adhesion; particles that come into contact with the filter fibers will adhere. Larger particles will be forced to embed directly within the filter upon impaction. However, smaller particles will collide with gas molecules, impeding and extending their path through the filter increasing their opportunity to impact filter fibres. The use of filters is critical in preventing the spread of airborne bacteria and viral organisms, and therefore in the prevention of infection.