When working with infectious materials and organisms in the laboratory, safe handling and appropriate training are of utmost importance. Another central component is personal protective equipment designed to prevent contact with tissue, liquids and aerosols and protect the wearer.
Depending on the biological safety level set for the laboratory facility, employees might be allowed to wear their own street clothes (for biosafety levels BSL-1 and BSL-2), but they must also put on a laboratory coat on top of this layer. Biosafety level 3 laboratories (BSL-3) require a tie-back or solid-front wraparound gown, scrub suits or coveralls and closed-toe shoes. It is important for personal protective equipment to be customized. This means it must only be worn by the designated employee the gear was fitted for.
The use of personal protective equipment is always subject to the materials and the hazard they present. Not all biological agents require full-body protection. At any rate, lab coats and coveralls must prevent the wearer’s clothing from biocontamination. There must also be a separate changing room. Work clothes are collected here and distributed for laundering or disposal.
To guard from chemical splashes, associates should also wear eye protection. Options include safety goggles and face shields. Face masks are used to cover the mouth and nose area. However, these masks do not offer respiratory protection against aerosols containing pathogens. This requires special system filters. They must be able to filter out infectious particles or droplets that are smaller than 5 µm (microns) as some of them can spread across the work station.
Clean air thanks to particle filters
The simplest and best solution in this case are so-called FFP3 masks (FFP stands for filtering face piece), which have to fit as closely as possible over the wearer’s mouth and nose. Filter materials behind the exhalation valve vary and include activated carbon, which filter many particles from the air. The major drawback of these masks is that they must be tight-fitting. The fit largely depends on the wearer’s physiognomy, but beards can be a problem in this case. What’s more, breathing is difficult if the mask is worn for long periods of time.
Another alternative are wearable filter systems, which can be combined with helmets or hoods and a tight, secure-fit visor. They use HEPA (high efficiency particulate air) filters to purify the air by using fiberglass fibers to trap and capture particles that are smaller than 1 µm. These systems make breathing easier and provide a better and more secure fit than FFP3 masks. Generally, however, this equipment cannot be worn indefinitely because it is physically demanding and the filter materials don’t last forever and have to be changed.
To prevent biological agents from escaping the lab or avoiding exposure, labs typically use so-called biosafety cabinets or microbiological safety cabinets. This is an enclosed, ventilated laboratory workspace that can be adjusted by positioning the safety glass sash. The employee works in the space that’s created under the opened window sash. To prevent the escape of aerosols, the air is extracted from inside the cabinet and passed through a particulate air filter. Laminar airflow provides an extra layer of protection. Air is blown from the top of the hood straight down and suctioned. This airflow serves as an additional barrier against particles from inside the biosafety cabinet. It is very precisely adjusted and can be easily disturbed by devices inside the cabinet or external turbulence in the lab such as the air conditioning system.
An even safer option is a totally enclosed, ventilated cabinet with leak-tight construction and attached rubber gloves for performing operations in the cabinet. Materials have to be brought in and removed through an airlock. Both types of biosafety cabinets are maintained under negative pressure and supply air is drawn in through HEPA filters. This ensures that aerosol generated within the cabinet is contained within the cabinet even in case of damage.
Personal protective equipment – Building block of a safe workplace
These measures protect workers in the laboratory. They vary depending on the specific substances used and the potential hazard they pose. Added to this are organizational precautions including lab-specific training of employees, access controls, cleaning and disinfection measures, as well as structural provisions, such as the safe operation and allocation of spaces within the laboratory as designated storage spaces or changing rooms. This also includes the spatial separation of the laboratory work area and – for biosafety levels BSL-3 and BSL-4 - safe building services that filter and sterilize exhaust air and waste water and guarantee the safe disposal of waste and incidentals.
Personal protective equipment and work practices are just two building blocks of the overall laboratory safety principles and concepts that – combined with the application of many other safety precautions - address the safe handling and containment of infectious microorganisms and hazardous biological materials.