On March 17, the US Environmental Protection Agency (EPA) published a best practice guide for improving indoor air quality and reducing the risk of spreading dangerous airborne particles. The guide – developed in collaboration with the Department of Energy, Center for Disease Control and Prevention (CDC), and other federal agencies – builds on the Biden-Harris Administration’s National COVID-19 Preparedness Plan, a roadmap to move the country forward safely as Americans get back to their normal routines.
The fact that Indoor Air Quality is now firmly on the political agenda should be applauded, as should the government’s provision of financial support via the American Rescue Plan and Bipartisan Infrastructure Law funds. And yet, it’s only one small step towards cleaner indoor space when larger strides are long overdue.
EPA’s Clean Air in Buildings Challenge contains a set of four broad recommendations:
It’s very encouraging that in-room air cleaning devices are featured at this high level. However, from this point onwards the guidance on air purification raises some big questions.
The next level of guidance on air purification is potentially misleading :
“Use portable air cleaners to increase air cleaning rates in areas where air flow and central filtration are insufficient:
When selecting ‘appropriately sized’ devices for the space, it’s critical to match the cubic meterage of the room to the air purifier’s clean air delivery rate. Many small air purifiers will be inadequate even to clean the air within a small bedroom, let alone a larger space. The reference to choosing the quietest air purifiers is nothing short of dangerous. Quiet can mean ineffective. It’s a real technical challenge to clean all the air in the room, not just the air around the unit itself, and it requires a robust fan that will inevitably make some noise, as well as smart engineering to avoid creating exhaling drafts. Many air purifier products advertise that they have a ‘whisper’ or ‘sleep’ fan setting, which emit very quiet 10 to 20 dBA of noise. What they don’t tell customers is that on that fan setting the volume of air being cleaned is very small, if any at all, as the low fan pressure is unlikely to be driving air through the filter.
Alarmingly, EPA advocates do-it-yourself air cleaners.This undermines the role of properly engineered air purifiers, not just the filter itself but the housing, which must prevent particles from bypassing the filter, and ideally the UV light that renders the filter harmless to touch. The web links point to additional guidance documents on air purification, but these focus entirely on residential air purifiers, which overlooks the biggest risk ie. spreading infection in shared public spaces.
In providing further guidance, it’s critical to learn from mistakes made to date. After spending $58m on 157,000 air purifiers, New York City public schools are reported to have seen a 23% rise in COVID-19 student case rates and a 29% rise in staff case rates when compared to buildings with stronger ventilation.
While HEPA filtration is proven and recommended by the CDC, air purifiers using unproven Disinfecting Filtration System (DFS) ionization technology were specified for the New York schools. This was despite a distinct lack of independent, third party testing to corroborate performance claims, even though the manufacturer claimed its technology to be superior to HEPA. A subsequent lab test by Brent Stephens – a professor and chair of the civil, architectural, and environmental engineering department at the Illinois Institute of Technology – apparently found that the device’s clean air delivery rate, a critical issue in a heavily occupied classroom setting, was inefficient compared to other air purifier products.
Specifiers must seek evidence of independent laboratory tests to validate performance claims. No health products should be specified without a body of evidence from recognised institutions, preferably backed up by real-world trials.
The EPA guidance does not provide an unequivocal steer on appropriate, proven and safe technologies. Leading health authorities including the CDC recommend NOT to use, or to exercise extreme caution with, air purifier technology that is ‘additive’ in nature i.e. adding chemicals to the air, however safe they claim to be. This includes units that use ionization, plasma or titanium dioxide. The agencies state that there aren’t enough long term studies that demonstrate the safety of these products and how these technologies impact indoor air gases and a room’s air environment.
A Massachusetts Institute of Technology (MIT) independent research study published in October 2021 found that Volatile Organic Compounds (VOCs),including formaldehyde, actually increased after four air purifiers with ionization and plasma technology were used.
In any case, research studies demonstrate that HEPA filtration is the most efficient air
filtration technology, tried and tested over many decades and endorsed by NASA. This is why the WHO, CDC and other authorities only recommend using HEPA, and in certain cases UVC, which are defined as ‘subtractive’ technologies.
Nine out of ten people breathe air with levels of pollutants that exceed the World Health Organization’s guideline limits. The call to action to improve Indoor Air Quality and protect public health is welcome and is no doubt a step in the right direction, not just because of Covid but because of the wider detrimental impact of polluted indoor air. But the EPA guidelines are flawed and don’t go far enough.
The White House statement seems to acknowledge that limitation in stating that: “The Administration will launch efforts to explain what good ventilation and air filtration look like as an important component of helping to reduce disease spread, and how buildings of any kind can pursue improvements to their ventilation and air filtration strategies.”
The nation’s health is at stake here.Taking one small step towards better Indoor Air Quality for everyone was long overdue. What we now need is regulation or, failing that, meaningful engagement between the government and the country’s (and wider world’s) leading Indoor Air Quality academic community.
With closer collaboration, one small step towards cleaner indoor space can become a giant leap.
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