As more labs look to optimise their resources and reduce spending, improving the longevity of replacement elements, like filters, can provide immense opportunity within the lab environment. Class II biosafety cabinets (BSCs) use fans and filters to provide personal protection from biological hazards while creating a particle-free work area. The fans control airflow and establish an air barrier in the cabinet front opening that keeps hazardous airborne materials inside the BSC and room contamination out. The high-efficiency filters capture particles to provide clean downflow in the cabinet work area and prevent hazardous particles from escaping the cabinet in the exhaust.
But the fans and filters are in conflict. Filters load, or fill up as they capture particles, which increases resistance to airflow and taxes the fans. Fan speeds are then increased to restore airflow, but eventually, the fans are at full speed, and loaded filters must be replaced.
A study showed less than 2% of cabinets required filter replacement each year
At the Annual Biosafety Conference of the American Biological Safety Association in 2013, Cope, Osorio-Sanchez, Gibson, and Wright presented an analysis of BSC service at the National Institutes of Health (NIH). They reviewed over 10,000 certification reports from 2005 to 2010 and found that less than 2% of cabinets required filter replacement each year.
This suggests that, in many cases, the filters in BSCs last much longer than the fifteen-year recommended lifespan of a BSC (NSF International, 2024, p. 125). So, what affects BSC filter life and how can a cabinet’s filter life be extended?
Use and stand-by
Sixty-three users and cabinets at a North American university were surveyed to assess the energy consumption of their cabinets. Phillips explained in the 2015 paper that the average cabinet use was 17.6 hours per week, and 43% were used less than 10 hours per week. Filters might last much longer than expected because cabinets are operating less than we anticipated.
Standby is the state of a BSC when not in use, particularly overnight, and when no one is in the laboratory. Some recommendations suggest that the continuous operation of fans on BSCs not connected to external exhaust will reduce airborne particulate in the laboratory (U.S. Department of Health and Human Services, 2020, p. 380). The same recommendations specify complete surface decontamination within the BSC work area before and after each use. Assuming the effectiveness of this, the major remaining benefit would be improved air cleanliness in the laboratory.
Standby is the state of a BSC when not in use, particularly overnight
A sustainability survey found that 28% of users leave the cabinet on standby continuously. Continuous operation means the cabinet in use eight times more per week than the average. Modern cabinets often have the capability for reduced-flow standby modes, where the cabinet window is closed and airflows are reduced. Reduced airflow would provide extended filter life in comparison to operational airflows when not in use.
Window height
The primary source of the particulate load to the filters is
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