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Biological safety cabinets, decontamination or sterilization with paraformaldehyde
R Fink1, D F Liberman, K Murphy
1M.I.T., Environmental Medical Service, Cambridge, MA 02139.
American Industrial Hygiene Association Journal
|June 1, 1988
Summary
Formaldehyde decontamination of biological safety cabinets requires at least 4 hours for sterilization. Longer exposure times, like 6 hours, ensure formaldehyde penetrates HEPA filters for effective spore inactivation.
Area of Science:
- Microbiology
- Environmental Science
- Laboratory Safety
Background:
- Biological safety cabinets (BSCs) require effective decontamination to maintain sterile environments.
- Formaldehyde gas is a common sterilant used for BSC decontamination.
- Determining optimal exposure times is crucial for ensuring sterilization efficacy.
Purpose of the Study:
- To establish the minimum effective exposure time for formaldehyde gas to decontaminate biological safety cabinets.
- To assess the impact of formaldehyde exposure duration on the inactivation of Bacillus subtilis var. niger spores.
- To evaluate formaldehyde penetration through High Efficiency Particulate Air (HEPA) filters.
Main Methods:
- Bacillus subtilis var. niger spores were utilized as biological indicators.
- Spore strips were placed inside BSCs and exposed to formaldehyde gas for varying durations.
- Sterilization efficacy was assessed by quantifying log reduction of spores post-exposure.
Main Results:
- Formaldehyde contact times under 3 hours were insufficient for complete sterilization.
- A reproducible killing of spore strips was achieved with formaldehyde exposure of 4 hours or more.
- Exposure to formaldehyde for 6 hours allowed sufficient gas diffusion through HEPA filters to sterilize strips with lower initial spore counts.
- A minimum of 5 to 6 logs of spore killing was observed after 4 to 6 hours of treatment.
Conclusions:
- A minimum formaldehyde exposure time of 4 hours is recommended for effective biological safety cabinet decontamination.
- Extended exposure (6 hours) ensures sterilization efficacy, including penetration through HEPA filters.
- Formaldehyde decontamination protocols should be optimized based on exposure time to guarantee microbial inactivation.