Without significant improvements to Indoor Air Quality (IAQ), COVID-19 infections may spike again, a consulting engineer has warned.

Jeremy McDonald, a professional engineer with New York-based firm, Guth DoConzo Consulting Engineers, said everyone needs to get serious about IAQ to stop the spread of COVID-19.

"The challenge with getting people to pay more attention to indoor air quality is that the problem is an invisible one making it hard to understand. That makes it even more dangerous especially in a pandemic fuelled by airborne droplets,” McDonald said.

He said the indoor air conditions that existed at the start of this year are unchanged, no improvements have occurred since the pandemic began.

While masks, social distancing and disinfecting surfaces are effective tools in the fight against COVID-19, McDonald said there should also be strategies focusing on indoor relative humidity and quality air circulation.

“Like most viruses, the SARS-CoV-2 coronavirus that causes COVID-19 needs very low or high relative humidity to propagate,” he said.

In a whitepaper published earlier this month titled "Mitigating COVID-19: A Better Path Forward; Addressing Indoor Air Quality Issues to Reduce the Impact of the Pandemic," McDonald calls attention to widespread HVAC problems and introduces strategies to address them.

He points out that low air circulation is a problem in many modern buildings.

“Like a stagnant pond, a room with no airflow will allow pathogens and toxins to build up, ultimately creating a toxic environment for its inhabitants. Good air circulation, on the other hand, will whisk away toxins from a room like a running stream of water,” McDonald said.

Most office buildings are ventilated to have up to two air changes per hour, so that fresh air from outside purges the indoor air every 30 minutes, maximum. The more fresh air purges per hour the better from an infection control perspective, since this will reduce the concentration of the virus.

The problem, McDonald notes, is that a lot of buildings suffer from a lack of routine maintenance or aged equipment which doesn’t provide the recommended air exchanges.

“Without proper management of indoor air quality (IAQ) the actual air flow to a building may be far less than it’s designed to have, which allows this nasty virus to increase in concentration,” he said..

Scientists long ago established that viruses, bacteria and other toxins propagate either with low or high relative humidity.  Viruses typically struggle to propagate when relative humidity is moderate, between 40 per cent and 60 per cent relative humidity.

As relative humidity is lowered in buildings, people's noses, throat, and lungs become drier. In addition to being an irritant, this drying effect results in less resistance to viruses and bacteria.   
As air is warmed, its ability to retain water is increased — lowering the relative humidity of the air. This is why viruses are their most deadly over the long winter months in the Northeast, as we spend more time in the warm and dry confines of our homes and buildings.

“For an office building, it's really hard to get to 40 percent humidity on a bone dry, 5 degree winter day. But even getting to 30 per cent humidity would help a lot in reducing the intensity of the virus,” he said.



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