ACR Journal

CM YK / .ai CMYK / .ai CMYK / .ai acrjournal.uk 31 AIR TREATMENT modifications to the HVAC system. The vast majority of UK buildings don’t even have centralised recirculating HVAC systems, so UV treatment is neither appropriate nor necessary in these instances. UV fitted in recirculation systems is not seeing mass-deployment as the systems use too much energy and take up too much space. So why were these solutions o ered if there are so many issues? Part of the reason that advice regarding UV and HEPA filters came out relatively quickly is that it’s easy to test UV exposure and HEPA filters’ e ectiveness on a small scale and then extrapolate that to working environments. But clearly, that doesn’t mean they’re the right solution for every application. So what can we do? Naturally, the first thing people do is follow the issued advice, especially if they’re responsible for reducing risk in a business. But if they try to do this and find they can’t, for whatever reason – too expensive, too uncomfortable, completely impossible – of course, the next step is to go looking for other solutions, and luckily, there are plenty of deployable options to consider. Find solutions that are active in the space Despite early fears, there isn’t much evidence of significant super-spreader events linked to centralised HVAC systems. For that reason, if you want to reduce risk, deploying systems fitted in the air handling unit isn’t the most appropriate option. Instead, you’re better o deploying solutions that are active in the space. Let’s recap pass-through technologies: with these, you have to wait for air from the room to be brought back to the air cleaner. This means that you are reliant on air changes per hour. Moving large volumes of air around not only uses a lot of energy but also increases noise. When it comes to UV systems fitted to recirculating HVAC systems, for example, they are reliant on having su’cient dwell time, which is not always feasible due to size limitations. A better option is germicidal technologies active in the space, such as upper room ultraviolet systems and bipolar ionisation. In addition to reducing risk from airborne pathogens, the latter improves a range of indoor air quality parameters, further increasing its attractiveness as a solution. However, it should be noted that it needs careful integration with the HVAC system to work e ectively. With these germicidal technologies, there’s no need to wait for the air stream to enter the air cleaner, as the reaction with in-room contaminants starts to happen almost instantaneously. In reality, these are the type of systems that are eventually seeing adoption after duct- mounted HVAC and HEPA have been investigated and found to be impractical. Energy usage Extensive use of air cleaning technologies came about because of the oil crisis. Previously, there hadn’t been much consideration, but as oil became more expensive, people became increasingly concerned about energy expenditure. Take a UV system in a fan coil unit, for example. There are great results of it destroying the virus, but it undoubtedly uses a lot of energy: in fact, the UV system required to be e ective on a single pass would use 150-200 watts. By comparison, a bipolar ionisation system uses less than 1watt. Things are the same but di erent now, people are still concerned about energy usage, but where previously it was all about money, now it’s about our planet. What we need is sustainable, long-term solutions It’s easy to suggest the solutions advised in the early days of the pandemic, because in theory, they make sense, and they will work very well – in a lab. How applicable these solutions are to our average UK HVAC system is where the challenge lies. Moreover, if this disease becomes endemic, we will have to deal with it regularly. Long-term solutions need to be deployed because it is clear that these short-term solutions that reduce the risk immediately aren’t sustainable. We must find appropriate solutions that don’t cost the earth (pun intended). airrated.co Active in the space - Bipolar ionisation installed within an air handling unit, reducing airborne pathogen risk and improving IAQ