Decontamination

Decontamination is accomplished by depolymerizing paraformaldehyde to form a gas, as recommended by the National Institutes of Health (NIH). The gas is then circulated throughout the cabinet and then chemically neutralized after the appropriate decontamination period.

Decontamination of Biological Safety Cabinets and other containment equipment is required:

• After a particular work project using infectious materials is completed.
• Before any maintenance work is undertaken on a cabinet.
• Before HEPA filter replacement.
• Prior to relocation of the unit to another area.
• After a major spill of biohazardous agent.
• Prior to storage.

Due to the potential for exposure to formaldehyde, an OSHA-classified carcinogen, decontamination should always be performed by a trained person. 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.

The expertise of a contractor is important not only from the safety standpoint but also in avoiding the pitfalls of incorrect decontamination technique. If an excess of paraformaldehyde is used, a white polymer residue can be produced on the cabinet walls. This residue may interfere with future research projects. Therefore, precise calculation of the amount of paraformaldehyde needed is imperative. Furthermore, the temperature and humidity inside the unit must be carefully regulated to ensure maximum efficiency of the process.

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 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 safety glasses, face shield or goggles and a respirator with cartridges specific for formaldehyde exposure.

Paraformaldehyde must be neutralized with Ammonium Bicarbonate 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.

After decontamination a certificate is affixed to the cabinet and a copy provided for your records.