TTUHSC hosts Lunch and Learn on Biological Safety Cabinets
By Renee Witherspoon, CSP, CIH, CHMM, Past President South Plains Chapter (2012-2015)
On July 25, 2017 Texas Tech University Health Sciences Center (TTUHSC) in Lubbock again welcomed special guest speaker Bernard (Bernie) Schwartz, Product Specialist with the Laboratory Equipment Division of ThermoFisher Scientific. Bernie’s presentation was on Biological Safety Cabinets or BSCs. Kate McKee, MS, Territory Sales Representative with ThermoFisher was also present and assisted in the event. The program was a “Lunch and Learn” with ThermoFisher sponsoring the luncheon. A second hour of training was also provided where he focused on facility and engineering requirements for BSCs. This program was TechLinked to the regional campuses in Abilene, Amarillo, Permian Basin and at the El Paso main campus.
BSC’s and their Designations
A BSC is a primary containment device used when working with infectious microorganisms [Biosafety Level 2 (BSL-2) and 3 (BSL-3) agents]. BSCs are designed to provide personnel, environmental and product protection when appropriate practices and procedures are followed. Because it is a primary containment device, it must be routinely inspected and maintained to ensure proper operation. BSCs must be certified annually for sufficient airflow and filter integrity.
Bernie says that the “heart of the BSC is the HEPA filter.”
Most BSCs use high efficiency particulate air (HEPA) filters in the exhaust and supply systems. (The exception to this is a Class I BSC, which does not have HEPA filtered supply air.) HEPA filters remove particle sizes to 0.3 microns (µm) with an efficiency of at least 99.97%. To put 0.3 microns in perspective, a typical human hair is about 30 to 100 microns in diameter. Although these HEPA filters are effective in trapping particulates, they do not capture volatile chemicals or gases, hence cannot be substitute for a chemical fume hood.
There are three designations of BSC: Class I, Class II and Class III.
- The Class I BSC provides personnel and environmental protection, but no product protection. It is similar in terms of air movement to a chemical fume hood, but has a HEPA filter in the exhaust system to protect the environment.
- The Class II (Types A1, A2, B1 and B2) BSCs provide personnel, environmental and product protection. Because exhaust air is passed through a HEPA filter, it is particulate-free (environmental protection), and may be recirculated to the laboratory (Type A1 and A2 BSCs) or discharged from the building via a canopy or “thimble” connected to the buildings heating ventilation and air condition (HVAC). Exhaust air from Types B1 and B2 BSCs is discharged directly outside. Because these BSCs are not spark-proof, flammable chemicals should not be used in Class II, Type A1 or A2 cabinets because of the potential for vapor buildup, and possible fire or explosion. The Class II, Type B1 BSCs are many times used in research.
- The Class III BSCs provides the highest level of protection when working with highly infectious microbiological agents. It provides maximum protection for personnel and the environment. These cabinets are gas-tight and require the use of long rubber gloves attached in a gas-tight manner. There is access to the BSC for passage of materials through a dunk tank or autoclave. This BSC is a total-exhaust cabinet, so both the supply and exhaust air is HEPA filtered.
For more information on understanding the differences in the types of BSCs see ThermoScientific.
Risk Assessment, Work Practices and Recommended Procedures
To identify hazards and risk factors to personnel, the key is to conduct a risk assessment. In a risk assessment the work to be conducted and the laboratory environment are evaluated to identify potential hazards so that any risks identified are minimized. Researchers use the BMBL to assist in completing the assessment.
Importantly researchers should also include the appropriate methods of decontaminating materials and disposing of waste materials that are removed from the BSC once the work is completed. 20 to 30 minutes is generally considered an appropriate contact time for decontamination, but this depends on the agent used and should be part of the risk assessment process.
Recommendations for working in a BSC:
- Prepare a written checklist of materials necessary for a particular activity and placing required materials in the BSC before beginning work.
- Good microbiological techniques should always be used when working in a BSC to minimize splatter or creation of aerosols. Rule of thumb – Keep clean materials at least one foot away from aerosol-generating activities will minimize the potential for cross-contamination.
- Maintain workflow “Clean to Dirty.”
- All materials should be placed as far back in the cabinet as practical,
- Store only materials and equipment needed immediately in a BSC because of the potential for disruption of airflow.
- Personal Protective Equipment (PPE) should include use of lab coats and suitable gloves. Increasing levels of PPE may be warranted as determined by the risk assessment.
- Remember to move arms in and out of the BSC slowly, perpendicular to the face opening to reduce risk of contamination.
- Hands should be washed whenever gloves are changed or removed.
- The surfaces of all materials and containers placed into the cabinet should be wiped with 70% ethanol to reduce the introduction of contaminants to the cabinet environment.
- Small spills should be handled immediately by removing any contaminated absorbent paper and placing it into the biohazard bag or receptacle.
Ultraviolet (UV) Lamps and Testing
Many BSC’s have UV or germicidal lamps installed in them. The lamps emit light from the UV-C portion of the ultraviolet spectrum wavelengths that destroy bacteria, viruses and other microorganisms. The wavelength with the greatest lethal effectiveness is 253.7 nanometers (nm) which defines the germicidal category.
According to the BMBL, use of UV lamps are “not recommended in BSCs, nor are they necessary.” But if they are installed, they should be cleaned. They also recommend weekly checks with a UV meter to ensure proper operation frequency. When the laboratory is occupied, UV lamps should be turned off to minimize exposure to the skin and eyes.
To test the UV lamp, the surface on the bulb should be precleaned with 70% ethanol. After five minutes of operation, the sensor of the UV meter should be placed in the center of the work surface. The radiation output should not be less than 40 microwatts per square centimeter at a wavelength of 254 nm.
Bernie’s presentation covered the basics of BSCs in protecting laboratory working and their immediate environment from potentially infectious microorganisms. The added benefit is that researchers and investigators utilizing these best practices also protect the integrity of their work product in minimizing cross-contamination.
A properly maintained and certified BSC is a first line of defense in protecting personnel. Used in conjunction with appropriate practices and procedures will reduce the risk to laboratory employees.
To promote a safe and healthy workplace we as safety professionals need to be familiar with proper procedures, inspection and maintenance of each BSC we have at our facilities.
Thank you to Bernie, Kate and the ThermoFisher team for providing an excellent training program and resources for the research community.
Thank you also to Mark Welborn, TTUHSC Coordinator with Classroom Support for his assistance in the video production.
Biosafety in Microbiological and Biomedical Laboratories, Appendix A: Biological Safety Cabinets https://www.cdc.gov/biosafety/publications/bmbl5/bmbl5_appendixa.pdf
Additional resources and training:
A link to our second hour extended session video will be available soon. Will update our website once it is available.