ACR Journal

April | May 2021 AIR TREATMENT 30 It’s been just over a year since the restrictions related to Coronavirus were first put into place, during which, there has been a lot of guidance for how to operate buildings safely. Adam Taylor, Chief Innovation Officer of indoor air quality certification provider AirRated, reviews which of these methods are most likely to be applied. Delivering safe environments: the challenges of falling into line Volume 7 No.3 It’s no secret that proper ventilation has been key to reducing the transmission of the coronavirus. However, since the beginning of the pandemic, following the advice from government and industry bodies has been challenging. The initial guidance was to open windows, then to make use of high e ciency particulate air filters (HEPA) and ultraviolet light systems. Both of which are promoted by The American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE), The Chartered Institution of Building Services Engineers (CIBSE) and Scientific Advisory Group for Emergencies (SAGE). Turning o thermal wheels in heat recovery ventilation was also advised early on in the pandemic. All of this advice is, of course, scientifically valid. But there’s a gap between what’s advised and what’s possible. These solutions are just not easily deployable for the majority of businesses and people. The challenges of doing the simple things Sometimes things aren’t as simple as they sound. In the UK, for example, it’s not that easy to just tell people to open the windows to ventilate their homes. There’s a pervasive concern in this country about saving energy or ‘not letting the heat out’. The fact is, windows only need to be slightly opened to significantly improve indoor air quality and, in doing so, not aecting the overall temperature of the space. The interplay of advice is confusing, and when confused, people will revert to the thing they’ve been told the most and for the longest: keep the heat inside the house. More to the point, in many of our o ce buildings, the windows simply cannot be opened. Since the 1970s, buildings have been built to be more and more energy e cient, so many of us work in hermetically sealed boxes. Yes, it’s more economical and environmentally friendly, but the old ‘open the windows’ line just doesn’t apply here. Mechanical ventilation: not always an easy fix I hate to state the obvious, but it seemingly bears repeating - you can’t just increase the ventilation rate on some buildings. There are other things to consider, such as the amount of noise that brings, energy usage, and whether you can heat that building in doing so. There’s also the issue that in many parts of the country, the fresh air that would be brought in isn’t that fresh at all. HEPA filters Using HEPA filters to remove particles is excellent for general health benefits. Still, there is little evidence that the virus is spread through centralised heating, ventilation and air conditioning systems, so they’re not the best option for the situation we’re in. Furthermore, you can’t simply take an existing ventilation system and upgrade it to a HEPA filter. The system is unlikely to cope with the increased pressure drop, so it brings in less air and therefore increases the risk of transmission. Thermal wheels The knee-jerk reaction from many sources was to turn o the thermal wheels installed in the energy recovery ventilation plant. This advice was fine when first issued in mid-spring, but when applying to the United Kingdom, there’s only a tiny window of time when this is a viable option. With thermal wheels turned o, cooling systems had to work harder in the summer, and heating systems could not cope in the winter. Fortunately, this didn’t present a significant comfort issue as buildings were largely unoccupied. Very soon, however, people will start returning to work en masse, but we still won’t be out of the woods with the coronavirus. Ventilation will always be essential, and if thermal wheels remain switched o as advised, the heating and cooling systems will have to perform outside of their design parameters to deal with the loads. Ultraviolet systems UV systems do have good pass-through kill rates for pathogens, but they also require a lot of energy and heavy