Evidence has accumulated over the years that following the standard guidelines and codes for designing healthcare facility ventilation systems is far from sufficient to ensure a sterile environment. Sterility is generally defined as 6 log (99.9999%) reduction of a population of microorganisms. This means that as little as one microorganism in a million is expected to survive after disinfection.

Traditional air filtration with high-efficiency particulate air (HEPA) filters or ultra-low penetration air (ULPA) filters have been widely adopted in the ventilation systems of hospitals, labs, and clinics, to control airborne pathogens. However, multiple studies have demonstrated that despite the use of such high-end filters, viral and bacterial airborne contamination are still ubiquitous in these ventilation systems. 

The most common explanation for underperforming filters often points to the filter rack seal joint’s bypass, filter puncture leakage, and poor general installation or maintenance. Although all these points remain valid and can always be improved, the physical cause is rooted in the fundamental fact that all filters show a significant drop in their capture efficiency for a certain range of particulate sizes – these can include both particles which are too small to be captured by interception and impaction and those which are too large to be removed via electrostatic and diffusion. This is simply a straightforward consequence of the fundamental principles of filtration physics. […]

Read more on Health Europe website.