Ventilation is key for a safe return to the office

Paul Flanagan, Ireland managing director of Camfil, discusses the importance of HEPA filters and ventilation in transitioning the workplace from pandemic to endemic.

Paul Flanagan, Ireland managing director of Camfil.
Paul Flanagan, Ireland managing director of Camfil.

As Omicron started to ease in Ireland in mid-January, schools and businesses began returning to classrooms and offices. Consequently, crowded workplaces are common again as the country starts its phased reopening. Once more, HEPA (High Efficiency Particulate Air) filters became a hot topic. Are they effective, are they safe, is Covid-19 actually airborne, how much are they and what type should I purchase, were among the typical questions we heard in the industry. We also saw a lot of ‘epistemic trespassing’ which is a phrase used to explain how some industry experts pass judgment and offer commentary on products and issues where they lack expertise.

Trust and tests

By now, a lot of people know that HEPA filters in air cleaners do have a place in these environments and can effectively reduce aerosols containing Covid-19 or any other airborne viruses in a specific size range. The big issue we face today is the lack of accurate knowledge made available to business owners and school principals. The market is now well and truly flooded with several different air cleaner or air purifier-type products. Many opportunistic companies have manipulated a situation where they can easily convince a potential customer that their product is the most effective and that their studies and expertise should be trusted. What should really be trusted are the facts around HEPA filters. There is no good or bad HEPA filter. For starters, a filter can only be called a HEPA filter if it passes a strict test protocol which proves the filter’s ability to capture tiny particles, aerosols, and droplets in a determined size range at a specific rate of efficiency (normally measured in microns: µ). The test protocol itself, EN:1822/2019, also produces a certificate of compliance and should be issued with every HEPA filter supplied. The classification grades these filters are categorised to are H13 & H14. So there it is, it’s quite easy after all, everybody should ask about the test and demand a certificate in accordance with EN:1822/2019 is issued when purchasing these products. If a cert is not available, it most likely means that your supplier is not offering you a tested and certified filter.


Workers have returned to offices - Image © Prostock-studio -


Aerosols and airborne particles

When you are satisfied that the filter or filters are of the correct specification, all that is needed is a room-size calculation to determine that you will achieve a good level of air changes provided by the fan output in the unit and that you are happy with noise levels and aesthetics (adding three to five additional air changes per hour using an air cleaner will help reduce aerosols significantly). When the unit is running, in the case of an H14 HEPA filter, your certified HEPA filter will capture 99.995% of airborne particles at a Most Penetrating Particle Size (MPPS) efficiency which is all particles in a size range between 0.12µm – 0.18µm on the first pass. Covid-19 aerosols are typically measured at 0.15µm, and do attach themselves to larger particles making it a bit easier to capture them on the first pass through a certified HEPA filter. MPPS is typically used when testing HEPA filters that strive to achieve a H13 or H14 grade. Filters with a MERV 13 or ePM efficiency grade should not be confused with H13 filters, as they are universes apart in relation to their ability to capture aerosols containing viruses such as Covid-19 on the first pass through the filter, the H13 being the superior one of course.


What is also important to remember is that air cleaners containing certified HEPA filters are only part of the solution. They can and should be used where there is poor ventilation or where no existing HVAC is present. They act as a supplement to open windows which need to remain open where feasible for as long as possible to reduce CO2 levels and bring in oxygen. Buildings with existing and effective HVAC systems can make adjustments to provide a 100% filtered fresh air supply and avoid any recirculation loops - this is an ideal situation. It will ensure a more natural and more controllable air change scenario which will most definitely reduce airborne viruses. Air cleaners should be considered as a supplement to a HVAC system that is not effective or cannot be controlled in a way to avoid recirculation of air that may contain airborne viruses.

Hand hygiene and housekeeping

All other measures practiced during the higher level of restrictions phases should still be adhered to where and when possible in schools and any workplace within reason, at least until we are at zero level, which is probably never going to happen according to some experts. Although we are all looking forward to getting back to normal, I believe that the hand sanitation dispensers should remain everywhere, and should be used as often as possible by everybody. Long before Covid-19, hand sanitising was the number one piece of guidance given by hospital estates and infection control managers and that remains today. Hand hygiene is the simplest and most effective measure for preventing virus-associated infections, so we can learn something from that. While nobody likes wearing a mask, I suggest that they are essential in schools and crowded workplaces at least until we can introduce more natural ventilation which will become easier in the warmer seasons by opening windows fully and that is thankfully not so far away. Air cleaners using certified filters can still be operated during the warmer seasons which improves the situation further. They can be switched off or set at lower speeds, but if schools and businesses have them, why not use them at all times? Constant use will reduce the possibility of cases rising again and having them in place is a good strategy in preparation for another variant or spike which, of course, nobody wants to see.

Many workplaces will look and feel a lot different when we all finally return. Most of us will be cautious and a bit nervous about how we go about our everyday tasks. While very strict protocols should start easing, good housekeeping should always prevail. Cleaning regimes and overall discipline in the area of hygiene and awareness should be commonplace and whether we like it or not we all have our part to play.


About the author

Paul Flanagan is the Ireland managing director of Camfil, a provider of clean air solutions that aims to protect people, processes and the environment. Paul has nearly 30 years of experience working with HEPA filters in Ireland.