Keeping a Clean Atmosphere in your Laboratory Environment
Protecting workers from exposure to harmful materials or practices is a key part of any manager’s duties. While the Control of Substances Hazardous to Health (COSHH) regulations lay down guidelines on when protection against a certain chemical or particulate is required, they do not provide guidance about which type of containment or extraction system is the most suitable in a Clean Atmosphere.
Therefore, this article attempts to provide a checklist against which the choice of chemical or biological containment cabinets may be measured. However, the benefit of an expert evaluation of the hazards and risks to be considered before any equipment is selected should not be underestimated. Critical components of many laboratories’ environmental controls, chemical or biological containment cabinets are designed specifically to minimize employee exposure to chemicals and particulates – though rarely at the same time.
Let’s first deal with the main groups of products designed to protect against chemical hazards:
- Recirculating Filtration Fume Cupboards
- Ducted Fume Cupboards
- Group 1 – A biological agent unlikely to cause human disease.
- Group 2 – A biological agent that can cause human disease and may be hazardous to employees; it is unlikely to spread to the community and there is usually effective prophylaxis or effective treatment available.
- Group 3 – A biological agent that can cause severe human disease and presents a serious hazard to employees; it may present a risk of spreading to the community, but there is usually effective prophylaxis or treatment available.
- Group 4 – A biological agent that causes severe human disease and is a serious hazard to employees; it is likely to spread to the community and there is usually no effective prophylaxis or treatment available.
To deal with these different threat levels, three classes of Microbiological Safety Cabinets (MSC’s) have been developed.
Like a traditional fume cupboard or carbon-filter fume cabinet, a Class I MSC sucks air into the cabinet and away from the operator in order to generate a very high level of protection. However, unlike the ducted fume cupboard, all the exhaust air must pass through a filter before it is released to the atmosphere. High Efficiency Particulate Air (HEPA) filters are used for this purpose and are usually fitted immediately above the working area in modern cabinets. Suitable for material in groups 1 – 3 above, the Class I cabinet would be used typically in laboratories where patient specimens are handled prior to the identification of any disease.
Also suitable for Group 1 and 2 materials, and Group 3 material at the discretion of your Safety Officer, the Class II biological safety cabinet offers a high degree of operator protection through the mechanism of drawing laboratory air quickly around and past the operator. However, the Class II MSC also attempts to protect the integrity of the material under investigation.
Class III Microbiological Safety Cabinets
Although we have said that the Class I and Class II MSC’s generate a high measure of protection for their operators, this is not absolute. Therefore, when working with Group 4 materials, a safety cabinet guaranteed to provide maximum security for the operator and the laboratory must be used. This is the Class III MSC.
Very similar to a Class I except that there is no front aperture, operators access the work surface and samples via sealed glove ports. All materials must be transferred in and out of the cabinet through a transfer hatch or hatches, which resemble miniature airlocks. Exhaust air is pulled through one or more HEPA filters and dumped to the atmosphere via a ducted exhaust fan and make-up air is drawn into the cabinet via a HEPA filter. Finally, these cabinets are also usually sited in a purpose built, high biological security laboratory. In this way, every avenue is covered in attempting to make sure that the material under investigation cannot escape to harm the operators or the outside world.