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How Airflow Affects Indoor Air Quality

commercial office room

Proper airflow in commercial buildings, apartment buildings, schools, or other public spaces has always been important to indoor air quality, but it has been even more crucial since the onset of the COVID-19 pandemic.

Over two years into the pandemic, proper ventilation has increasingly become a powerful tool in fighting the spread of the disease, in addition to more common techniques like handwashing, vaccines, masks, and social distancing.

‘Respiratory Backwash’ and the Importance of Airflow

According to Joseph Allen, the director of the Healthy Buildings Program at the Harvard T.H. Chan School of Public Health, one of the most challenging aspects of fighting the spread of disease indoors is visualizing how air travels in a building.

Allen compares it to cigarette smoke. “If I’m smoking in the corner of a classroom and you have low ventilation/filtration, that room is going to fill up with smoke, and everyone is breathing that same air.”

Because microbes like the coronavirus are as small as 0.1 microns, they can easily be carried large distances, up to 6 feet, by respiratory droplets as small as 1 to 5 microns, which can be expelled while breathing or talking. Even large particles, up to 100 microns, can be expelled while singing or coughing. This phenomenon poses quite a danger in enclosed spaces.

“Everybody in a room together is constantly breathing air that just came out of the lungs of other people in that room. And depending on the ventilation rate, it could be as much as 3% or 4% of the air you’re breathing just came out of the lungs of other people in that room,” Allen said.

This is what he calls ‘respiratory backwash.’ And these aerosolized particles are fully capable of carrying viruses and other microbes from person to person.

Max Sherman, a leader on the Epidemic Task Force for the American Society of Heating, Refrigerating and Air-Conditioning Engineers, says, “When you’re talking about an airborne disease, there’s the what’s right around you, you know, the sort of the people who, you know, can cough in your face, the 6 feet thing, and then there’s the broader indoor air, because indoor air is recirculated.”

Sherman suggests that improving indoor air quality is not that difficult. “You just want to reduce the number of particles that might be carrying COVID or any other nasty [virus].”

Ventilation and air filtering are the most efficient ways to do this. According to Allen, “We have hardly any transmission outdoors. Why is that? Unlimited dilution, because you have unlimited ventilation. And so, even in crowded protests or outdoor sporting events like the Super Bowl, we just don’t see superspreading happening.”

Bringing in fresh air and filtering out airborne particles in indoor spaces, commercial buildings, and other public spaces can reduce the spread of viruses, bacteria, and other disease-causing microbes.

Air Filtration and Ventilation

Healthy indoor air quality requires effective filtration and plenty of fresh air. To remove the most airborne particles, the American Society of Heating, Refrigerating and Air-Conditioning Engineers recommends air filters with a minimum efficiency reporting value (MERV) rating of at least MERV-13.

This means the filter is 85% efficient at removing particles from 1 to 3 microns from the air stream, which covers most disease-carrying respiratory droplets.

More efficient filters can remove larger percentages of airborne particles, over 99% for HEPA filters, but they may pose too much of a restriction on the HVAC equipment, reducing efficiency or causing system damage.

A facility can maximize its air quality by choosing filters with the highest MERV ratings that are compatible with the HVAC equipment.

Bringing in as much fresh air as possible is also important to dilute the number of diastase-carrying particles. Allen recommends monitoring carbon dioxide levels with a CO2 monitor to gauge the effectiveness of a ventilation system.

He recommends that CO2 levels be maintained below 1,000 parts per million, though he prefers 800 parts per million or lower. This may require adding make-up air units, economizers, or upgrading the current ventilation system.

Commercial Air Quality Services in New York City

When you need help designing and implementing effective air filtration and ventilation systems for your commercial or industrial facility in the New York metro area, turn to our experts at AFGO Mechanical Services.

We’re a leading provider of commercial HVAC services in New York City and beyond, and we have effective strategies that can help you control COVID-19 and prevent the spread of illnesses and diseases.

Our company has served the New York metro area since 1995, and we’re here to help with all your commercial heating and cooling needs.

Contact AFGO today to learn more about our commercial air quality services for your New York City business.

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