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#biosafety cabinets

2 public questions tagged with this topic.

Animal Tissue Culture 2

UV light in biosafety cabinets is mainly used for:

Ultraviolet germicidal irradiation emitting at 254 nm wavelength is installed in many biosafety cabinets and transfer hoods as adjunct surface decontamination method. Photons absorbed by nucleic acids induce formation of cyclobutane pyrimidine dimers and 6-4 photoproducts between adjacent thymine or cytosine residues, blocking DNA polymerase progression and transcription, thereby inactivating bacteria, mycoplasma, fungal spores and viruses deposited on stainless steel or plastic work surfaces. Decontamination occurs only on directly illuminated surfaces with sufficient intensity and exposure time, typically 30 minutes when cabinet empty, blower off, and no personnel present because UV causes skin erythema, keratitis, and accelerates plastic degradation. UV does not sterilize liquids, penetrates poorly through organic debris, does not provide white light for microscopy, does not heat samples, and cannot replace HEPA airflow. Modern BSL-2 guidelines emphasize chemical disinfection with 70% ethanol or quaternary ammonium compounds as primary method, recommending UV only as secondary measure and advising against reliance for sterility assurance due to shadowing effects.

Ref: CDC BMBL 6th Ed Appendix A: Biosafety Cabinet UV light limitations; Alberts Molecular Biology of the Cell 6th Ed UV DNA damage chapter.

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Animal Tissue Culture 2

HEPA filters are used in biosafety cabinets to:

HEPA, High Efficiency Particulate Air filter, is fibrous mat of randomly arranged borosilicate fibers that captures airborne particles via interception, inertial impaction, and Brownian diffusion. In Class II biosafety cabinets, laminar flow hoods and CO2 incubators, HEPA filters provide 99.97% efficiency for most penetrating particle size of 0.3 micrometer, with even higher capture for smaller and larger particles including bacteria, fungal spores, dust and aerosolized cell fragments. In BSC, intake and exhaust HEPA filters deliver product protection for cultures and personnel protection by filtering exhaust before release to laboratory or outside. Filtration is purely physical; microorganisms trapped on filter matrix remain viable until filter is decontaminated by formaldehyde fumigation or hydrogen peroxide vaporization during cabinet certification. HEPA does not kill microbes by chemistry, does not control humidity, temperature, or gas composition, which are governed by humidifiers and infrared CO2 sensors. Periodic integrity testing using dispersed oil particulate challenge and measurement of face velocity at 100 lfpm ensures protection.

Ref: Lodish et al. Molecular Cell Biology 8th Ed Chapter 9 Cell Culture Methods; NSF/ANSI 49 Biosafety Cabinetry: HEPA filtration 99.97% at 0.3 µm.

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