How Effective are the Biosafety Cabinet's HEPA and ULPA Filters Against the SARS-CoV-2?

Can it capture the SARS-CoV-2?

The SARS-CoV-2’s estimated size is around 0.12 μm, and there are doubts on the filter’s efficiency to capture the virus, especially with the HEPA filter. There is a common misconception that HEPA filters only capture particles with the size of 0.3 μm or larger. So here are some facts to prove the filter’s efficiency:

Particles with a size of more than 0.3 μm travel through the air filtration system and are retained within the filter due to inertia. While particles with less than 0.3 μm in size can be easily visualized to fly through the holes of HEPA filter. However, that is not the case. A fascinating interaction called Brownian Motion occurs and traps smaller particles as well.

What is Brownian Motion?

The Brownian Motion causes the particles to bounce around and collide with each other, making them move in a random pattern and eventually hit the filter fibers and become trapped. That’s why smaller particles are easier to catch in both HEPA and ULPA filters.

According to a test conducted by NASA (2016), HEPA-rated media provides superior performance by removing virtually 100% of particulates. Moreover, there is only a slight drop in efficiency for particle size of around 0.3 μm — particles of this size are called Most Penetrating Particle Size (MPPS) in filter standards.

MPPS is the specific particle size that is most difficult to be captured by filter fibers. It is small enough to follow the air stream around the fibers, but it has enough mass that the Brownian motion effects minimally. Thus, particles size with less than 0.3 μm is in fact easier to capture in the HEPA and ULPA filters.

How to maximize guaranteed protection of a BSC filter?

Proper and timely maintenance. Services such as filter replacement, preventive maintenance, annual certification, and decontamination should be carried out regularly for optimal equipment performance. Thus, maximizes user protection, especially when used in a COVID-19 laboratory.

Preventive Maintenance

Prevention is key. This service procedure prevents unexpected downtimes and failures through routine maintenance and early detection of problems. The following are the procedures done when performing a preventive maintenance:

Cleaning the work surfaces and walls with an appropriate disinfectant

Removing stubborn stains or spots on the worktop

Testing the audible and visual alarms

Checking the cabinet’s mechanical and electrical functionality for any defect
Decontamination

Ready and safe usage. Filter replacement, unit installation, and relocation require proper decontamination. The following sterilants are used:

Chlorine Dioxide

Hydrogen Peroxide Vapour

Formaldehyde (if requested by the client due to specific circumstances)