Raj Setty, PE, CxA, LEED AP, Setty and Michael Wolf, PE, CxA, LEED AP, Farnsworth Group, Inc. | September 30, 2020
COVID-19 has elevated attention toward the need to improve indoor air quality, particularly in restaurants, office buildings, and other shared spaces. As more energy companies pivot to expand their services into air quality improvements, what are some key strategies to employ?
We asked our partners at the AABC Commissioning Group (ACG), the largest body of independent, certified commissioning professionals, for their input. This is a sneak peek of further information that will be provided in ACG’s upcoming October 8th webinar “Indoor Air Quality in the COVID Era: Commissioning & Construction Considerations.” Register today with promo code “CEBN10″ for a 10% discount.
Please note: This is independent advice from certified professionals in this sector and does not represent official technical, legal, or public health guidance from CEBN.
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Indoor Air Quality in the COVID Era: Commissioning & Construction Considerations
There are three main ways to improve your indoor air quality:
How do we know filtration and dilution adjustments are working?
While you cannot state or test to see if the virus is in the air, you can test to see what particles sizes make it through the filter into the supply air and finally into your space. You can buy low cost particulate sensors and place them around your building or utilize a hand held particle sensor.
If you detect over 15 µg/m3 plus particles when sampling for 2.5 µm (PM 2.5) particles, there is good chance that your filter effectiveness is not where it needs to be to help mitigate the virus transmission. At that point, change the filter (target MERV 13) or plan on going to a higher MERV rating or install bi-polar ionization/corona discharge technology to make your filters more effective.
On the dilution field test, as your indoor air composition approaches the outside air composition, then we can ascertain, there is good dilution and outside air being introduced into your building via the HVAC or open windows. The EPA has a good interactive site on air quality which is interactive and has layers to turn on and off. Many buildings have some level of carbon dioxide (CO2) monitoring and this is a simple indicator of occupancy. If CO2 goes up, then it means people have exhaled into the space, changing the air composition of CO2 in relation to the outside air CO2 in your local area. There is no straight line quantification of virtal load based on CO2, but we do know that if an infected person or asymptomatic person resides in a room without any air changes, the viral load will build up over time as will the CO2.
By flushing the room air with outside air, you can lower the CO2 and thereby viral load in the airstream. So, try monitoring the CO2 after occupancy or during and adjust your outside supply to keep it in line with your local outside air CO2 level. Generally speaking, 400 ppm of carbon dioxide is in the atmosphere. But it will vary day to day, place to place.
As an example, if your HVAC ran at 100% outside air, then the CO2 levels in your space would be nearly identical to the CO2 levels of the outside.
Ultimately, the real answer to how is it working will be the control of the spread from classroom to classroom. It’s important to strive for HVAC mitigation of the virus and most importantly, the HVAC system cannot be a mode of transmission between rooms.
Building operators have to make the above operational changes and then test and tweak until the air quality is improved.
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ACG is tightly affiliated with the the Associated Air Balance Council (AABC) and the Energy Management Association (EMA). The ACG, AABC and EMA have provided certification and training to thousands of industry professionals over a period that collectively includes more than 73 years. Together, these Authorities in Building Performance sponsor CxEnergy 2021, the premier conference and expo dedicated to energy management and commissioning (April 20-23, Dallas/Ft. Worth, TX).
