Utilizing a precision thermo anemometer air velocities are checked to ensure proper operation of equipment per manufacturers recommendations, if required adjustments will be made.

A viable particle is a particle that contains one or more living microorganisms. These can generally range from 0.2µm to 30µm in size. Testing is achieved by capturing, colonizing and counting colony growth. Adapt utilizes a nondestructive impaction BioCulture pump air sampler. The sampling head is engineered in such a way to deliver sampled air to a contact plate with a Soybean-Casein Digest medium or (Tryptic Soy Agar/Broth), so as not to disrupt normal ambient airflow and more importantly, without rendering the microorganism non-viable. The contact agar plates are then incubated at 20-25°C for 5-7 days and then at 30-35°C for 2-3 additional days. The resulting colonies are counted and reported. Each sampling location requires approximately 10 minutes.

Because of the nature of the work involved, Biological Safety Cabinets must be decontaminated when:

1. Any service work is performed within the contaminated portion of the cabinet, i.e. HEPA filter change.

2. Moving the cabinet from one location to another.

3. After initiating a totally different work program.

4. After a gross spill of a highly concentrated research agent.

Decontamination is accomplished by depolymerizing paraformaldehyde in controlled temperature and humidity to form a gas. The gas is then circulated throughout the cabinet and is then externally vented or chemically neutralized after an appropriate decontamination period.

Due to the potential for exposure to formaldehyde, an OSHA-classified carcinogen, decontamination should always be performed by a trained professional. BSC users are strongly urged to hire a contractor to perform this function. Contractors experienced in this method are much less likely to run afoul of the stringent OSHA Formaldehyde Standard (29 CFR 1910.1048) than are lab workers who attempt this process on an infrequent basis.

Although the actual decontamination work is to be completed by a contractor, there are responsibilities which must be met by the lab supervisor. Building occupants who may be impacted by these activities must be protected against accidental exposure.

We ask that, in light of the risk of exposure, the lab supervisor oversee the preparation for the decontamination project. Ask yourself whether the contractor follows appropriate safety practices. For instance, are signs posted at the door to the laboratory indicating that decontamination is in progress and entry is limited? A warning sign should also be displayed at the face of the BSC to prevent someone from opening it during the procedure. M.S.D.S. sheets should be made available during the procedure by the contractor.

If the BSC unit is connected to building exhaust, the unit must be disconnected prior to decontamination.

The contractor charged with performing the decontamination should wear appropriate personal protective equipment such as full face respirator with cartridges specific for formaldehyde exposure.

Paraformaldehyde must be neutralized with Ammonium gas prior to venting the cabinet, after which lab personnel must rinse and wipe down all surfaces with pure clean water to remove any residue left by the process.

Biological Safety Cabinets (BSC) were developed because of the need for personnel protection not afforded by horizontal and vertical flow clean benches.

Like the clean bench, the BSC utilizes High Efficiency Particulate Air (HEPA) filters which have a 99.97% efficiency on particles of 0.3 micron size. There are three classes of Biological Safety Cabinets.

CLASS 1
The Class 1 Safety Cabinet is a modification of the chemical fume hood and provides protection to personnel and the environment, but little, if any, to the product.

Air is drawn through the work opening at a minimum average rate of 75 linear feet per minute (LFPM). The air is then exhausted through a HEPA filter. The Class I Cabinet can be used for low to moderate risk biological agents.

CLASS 2
The Class 2 Safety Cabinet was designed to provide personnel, environment and product protection. Product protection is achieved with the use of a supply HEPA filter, an exhaust HEPA filter and laminar (unidirectional) downward air flow. This minimizes air turbulence which prevents cross contamination in the product work area. Personnel protection is provided through a cabinet design that always maintains containment at the window opening.

There are four TYPES of Class II Cabinets. TYPES A1 & A2 and B1 & B2 are designed to recirculate a percentage of filtered air with the remainder being exhausted. TYPE A Cabinet is exhausted into the laboratory or externally. The TYPE B Cabinet must be exhausted through an external blower system. The third TYPE of Class II is a Total Exhaust Cabinet which, like the TYPE B, can be used with chemical carcinogens and low level radioactive materials. All three TYPES can be used for low to moderate risk biological agents.

CLASS 3
The Class 3 Safety Cabinet is a totally enclosed, self-contained, ventilated cabinet that operates at a negative pressure to the laboratory environment. Rubber gloves are attached and air enters through filters and is then exhausted through one or more HEPA filters. Incinerators are sometimes employed to provide greater protection to the environment.

Unlike the Class 1 and Class 2 Safety Cabinets, the Class 3 can be used for high risk biological agents, chemical carcinogens and low level radioactive materials.