Biological Safety Cabinets play an important role in laboratories by ensuring that workers, products and the surrounding environment are not contaminated by potentially hazardous materials like hormones, viruses and bacteria. BSCs also provide a sterile environment for the manipulation of sensitive materials. Because the cabinets are so crucial to the smooth functioning of a laboratory, it is important to keep them clean and free of contamination.
Regular decontamination of your BSC is good practice. Residues of bacterial endospores, fungi or viruses may remain after manipulations within the BSC; decontamination completely destroys these organisms, thereby sterilising the environment.
The decontamination described above is not the same as the daily disinfection of work surfaces and the outside sections of BSCs, which usually involves application of a cleaning fluid and the wiping off thereof. In theory this wash-down prevents cross-contamination within the cabinet, because the BSC is designed to trap pathogens in its filters. Anything that might escape and settle on the interior work surfaces would be removed by the wash-down. However, it is still necessary to perform decontamination in certain circumstances.
When to Decontaminate
Authorities recommend that decontamination be performed in the following situations.
Before Replacing HEPA Filters
Decontamination should be done before replacing HEPA (High Efficiency Particulate Arrestance) air filters in the BSC, to ensure the safety of the persons handling them. This is because contaminants may collect in the filters.
Prior to Maintenance and Certification
Decontamination must be performed before scheduled maintenance, as well as prior to performance tests or certification of the BSC. Part of a BSC’s bi-annual validation requires technicians to inspect the interior of the cabinet and replace the pre-filter media.
Technicians are not allowed to open a BSC without it undergoing decontamination. In fact, SABS regulations expressly prohibit service personnel from working on BSCs that have not been decontaminated if these cabinets have been exposed to harmful or hazardous organisms. Neglecting to perform a decontamination means that the inspection cannot proceed, which may lead to later problems due to blocked filters or undetected faults. This could prove costly and incur downtime while the BSC undergoes repairs.
Following a Spill
In the event of a spill within the cabinet, it goes without saying that decontamination becomes necessary.
It is important to decontaminate a BSC before moving it to another location, as moving increases the risk of leakage.
What Decontamination Involves
Because decontamination of BSCs involves working with both hazardous organisms and chemicals, procedures are strictly regulated by health and safety authorities and may only be performed by well-trained technicians.
When decontamination using fumigation is performed within the BSC, it exposes all internal surfaces, exhaust filters, plenums and fans to disinfectant. The BSC is sealed off for safety, humidified to between 60 and 85%, and formaldehyde gas generated within it, from solid paraformaldehyde. The process tends to take place overnight, as it requires approximately 17 hours.
Some companies are starting to replace the formaldehyde with chlorine dioxide gas, as the latter is odorless, non-carcinogenic and leaves no residue inside the BSC. It works much faster too, requiring less than four hours. Hydrogen peroxide is also being used. However, formaldehyde remains more compatible with, and less damaging to, the surfaces of the BSCs and is still a popular choice.
Vivid Air uses the latest decontamination kits available, these boil off the correct amount of formaldehyde after a delay timer has been set to allow all personnel to vacate the immediate area around the cabinet as well as a time delay neutralization phase using ammonia to neutralize the reside formaldehyde in the cabinet before the technicians break the seal to commence their service or validation of the BSC.
After the decontamination process has been completed, spore strips may be placed in the BSC before being removed and incubated in a special fluid for a week to check that there is no growth of organisms, and thus no more contamination in the cabinet.
Regular decontamination of your BSC is not only a responsible action in that it protects workers, product materials and the environment; it is also cost effective, as it helps prevent all manner of potentially expensive problems in the long run.
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