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Shocking numbers of people are still dying from covid in the UK, the USA and many other nations that have effectively let the virus run wild. As the pandemic continues, Time magazine has joined a growing number of publications, businesses and scientists starting to demand that we clean up our indoor air, and finally do it properly.
The good news is the pandemic will eventually end thanks to a blend of vaccines, infection-induced immunity, and personal safety measures. The bad news is we have a very long way to go, covid will probably stick around for decades or a great deal longer, like the common cold and flu. And, of course, this will not be the last respiratory virus pandemic. That’s a given.
Time magazine appeals for nations to ‘think clearly and scientifically’ about how to stop viruses like covid spreading indoors, especially where people have decided against masks. Sadly there are loads of rogue products around that cannot and will never work, with no scientific basis. Testing isn’t properly controlled, it is biased, it doesn’t compare itself to existing tech and doesn’t take place in real-world conditions. Happily there are some indoor air cleaning technologies that work beautifully. The challenge is to know the difference. Let’s take a look.
Facts about cleaning the air indoors so covid can’t spread
Many products claim 99.9% or more reductions in virus particles but they ‘compare test organism concentrations in air before and after passing through a device but not what happens in a room where the device would be used, which is all that matters in the long run’. Much of the time the test data isn’t available. It’s worrying that the rate at which decontamination occurs in rooms isn’t often mentioned. A device might say it achieves 99.9% but the fine print says the test was conducted over 24 hrs, no use at all when you’re in a room with someone who’s infected.
Clearance in minutes is the only way ahead for properly-cleaned indoor air. As you can imagine virus particles almost always stick around for longer indoors where the air doesn’t move and isn’t exchanged for fresh. If you breathe in an indoor setting where other people are also breathing, you will almost certainly breathe in some air that has just been breathed out by someone else. The percentage of recycled air in a room – the ‘rebreathed air fraction’ – is a good way to predict the risk of infection.
Ventilation is the main way to cut the risk of airborne infection indoors
For hospital airborne infection isolation the OS Centers for Disease Control and Prevention (CDC) says you need 6 – 12 room air changes per hour. Air changes remove contaminants but it’s also important to factor in the virus that gets added back in when infected people enter a space. The infectiousness of the virus also matters – the more infectious it is, the more air changes you need to keep indoor air safe. Experts say 6 – 12 air changes an hour might not be enough to stop the fast-spreading omicron from infecting people.
About older buildings without mechanical ventilation
Mechanical ventilation is designed for comfort, not infection control. It can’t achieve the air changes needed to combat the virus. Older buildings without mechanical ventilation can maybe achieve one air change an hour even with the window shut, simply because of draughts. Open windows can take the rate much higher. But windows are usually closed either by the occupants or the owners because of the weather, and the cost of heating or cooling the space. Because automated mechanical ventilation systems often only exchange small amounts of outside air, most of the air is re-circulated along with the contaminants it contains.
The relationship between ventilation and infection is interesting. Doubling the ventilation rate only cuts the contaminants by about half. When air contaminants are low, you need a lot more air movement to dilute and remove them. And the bigger fans, blowers, ventilation ducts and more you need to do the job are costly. Because the omicron variant requires ‘very high ventilation rates’ ordinary mechanical ventilation in public spaces isn’t enough.
What about other ways to disinfect against covid?
High-efficiency air filters can ensure less than 99.9% of dangerous particles is sent back into rooms. Adding UV, bipolar ions or cold plasma doesn’t make much difference. We already know that air recirculation in ventilation ducts isn’t helping covid spread. If you’re in a room with an infected person and the air will only be decontaminated after it has left the room, it’s not much help to you.
It makes more sense to quickly decontaminate the air in the room itself, where the transmission risk exists. And that’s why air-disinfection technology’s ‘enhanced in-room air decontamination’ is such good news. Increased ventilation, portable air cleaners, upper air germicidal UV and Far UV are all proven to be highly effective. While Ion generators work too, there’s much less evidence to back them up. More about that later.
GUV is unusually cost-effective
Compared to mechanical ventilation and room-air cleaners, GUV is cheaper and much more effective. It cleans loads of air at once, as much as 24 exchanges per hour in one controlled hospital study in South Africa, well beyond the capacity of most mechanical ventilation systems and room-air cleaners. The same results were seen in a test in Russia, where GUV came in at around 9.4 times more cost effective for the same amount of air. No wonder the US Department of Energy is supporting the commercial development and deployment of LED UV technology for disinfecting air and surfaces.
Make sure you buy proven LED UVC air cleaning technology
Not all GUV devices on the market are equal. Some just don’t work. Too many GUV devices for businesses and homes aren’t ‘evidence-based and are unlikely to be effective in reducing COVID-19 transmission’. If you see one for sale that goes around your neck, step away. There’s no way it can work, no scientific basis for it. The little boxes that are meant to disinfect mobile phones are just as useless. And GUV wands are so ineffective they’re described as ‘ irrational’. The GUV portals designed to disinfect people on the way into buildings are equally bad. They don’t make any sense since there’s no significant decontamination of skin or clothing and the virus, which lives inside us, can’t be eliminated from the outside. And there’s no point disinfecting the air outdoors, since the wind does that all on its own.
Ionization, as we’ve mentioned, comes with serious problems. The mechanism isn’t understood very well, which raises alarm bells. There are very few published independent studies. One, in Peru, revealed a basic ionization system was about half as effective as upper room UVC. But the room the study took place in was blackened with soot, ionised so it stuck to surfaces. Ionization can also make ozone from oxygen, which is dangerous and can lead to other toxic chemical reactions.
The experts recommend...
Indoors, air disinfection is a safe and efficient way to reduce covid’s spread. Combining the big three - mechanical ventilation, upper room GUV, and portable room air cleaners – makes a lot of sense.
The most effective of all is upper room UV, and it’s also the most cost-effective. It is ‘demonstrably safe and readily available to deploy today’. Far UV is also available, even safer and potentially more effective since it works around people and doesn’t depend on the air being mixed. Room air cleaners also have a role, in small spaces where the air can be exchanged at least 6 times an hour.
Getting ready now doesn’t just mean you future-proof your business against covid. It also means you’re in a good position to handle seasonal respiratory viruses, ongoing epidemics like TB, and the next pandemic.
As we all now know for sure, there will be another. It’s just a matter of when.