Reducing The Risk of COVID-19 in Buildings
Published by Benjamin Skelton
The global COVID-19 pandemic raises questions for us in the design, construction and operation of buildings regarding our role in reducing the risk of infection and curbing the spread of airborne diseases. While there is much more to be learned about the novel coronavirus, known as SARS-CoV-2 which causes the disease COVID-19, what we have learned thus far can be used to help us in the built environment do our part. So, to help you better understand some of the known facts about the novel corona virus and how it may impact you and your buildings Cyclone has created the following summary.
How is the Corona Virus Spread
Many infectious diseases spread through airborne paths such as influenza, colds and most recently, COVID-19. These are transferred from person-to-person by either respiratory droplets or from a surface to a person’s nose, eyes, or mouth. Respiratory droplets form when you talk, sneeze or cough. Tests performed by the National Institute of Allergy and Infectious Diseases, released in a correspondence to the New England Journal of Medicine, revealed the SARS-CoV-2 virus remained viable as an aerosol for three hours. On plastic surfaces it was viable for three days, stainless steel two days and cardboard 24 hours. This was in a laboratory setting and conditions such as daylight would reduce viability.
While all this sounds frightening, it’s manageable. Currently there isn’t a vaccine or drug that cures the disease, and the stores are void of hand sanitizers and toilet paper. But really the soap aisle is the one that should be barren. The anatomy of SARS-CoV-2 reveals that virus is protected by a lipid (fatty) bilayer membrane. Soap dissolves the fatty membrane and the virus quickly becomes inactive. That’s why the CDC recommends washing your hands for 20 seconds with soap. It’s currently the best defense.
So, what about the air around us? Previously I mentioned research that showed an aerosolized coronavirus particle could remain viable for three hours. Why does aerosol transfer matter? An aerosol consists of a liquid or solid (in this case the virus) suspended in a gas such as air. Think of a fog, where water particles are suspended in the air for long periods of time. Not all respiratory droplets are an aerosol. Preliminary studies believe SARS-CoV-2 can be aerosolized but other research isn’t finding any indication that is actually happening. It seems most respiratory droplets are quickly falling from the air in a matter of seconds and generally don’t travel further than six feet, as shown in this graphic from the ASHRAE Position Document on Airborne Infectious Diseases.
Authors Note: Image from ASHRAE Position Document on Airborne Infectious Diseases Updated February 2020
Should I be operating my building differently?
In general, building heating, ventilating and air conditioning (HVAC) systems can be operated in a manner that can increase the spread of infectious diseases or be used to control the risk to occupants. If coronavirus particles were being entrained in air distribution systems, it mostly likely is first being exhausted from the building or returned to air handling equipment. Most commercial buildings have handling equipment that introduces fresh ventilation air and filters it before distributing to occupied areas. The N95 face masks that are being used by health professionals are 95% efficient at removing particles as small as 0.3 microns. The SARS-CoV-2 virus is smaller than that on its own but is often attached to other particles.
ASHRAE’s position document suggests that installing air purifiers in high traffic areas may be beneficial, especially if there are a large number of at-risk occupants. This could be multi-family high rise buildings with an at-risk population or an office lobby. This approach may not yield beneficial results if the space has an air-change per hour (ACH) rate that exceeds six. Some air purifiers that use UV light may emit radiation and/or ozone, so their application should be carefully considered.
SARS-CoV-2 becomes inactive in daylight quicker than indoors. This is the effect of ultraviolet (UV) light. UV lighting is commonly used in laboratory, healthcare and some commercial HVAC systems. While UV helps kill this virus, consider installing UV light on your cooling coil to kill more common bacterial growth. Other application approaches to inactivate airborne diseases with UV requires careful design.
In air handling equipment, to achieve the same 95% efficiency, the filter rating would need to be MERV-16 which is nearly HEPA (high-efficiency particulate air) filter grade. Increasing filtration to a higher efficiency is a great method for cleaning the air being supplied regardless of infectious disease concerns. Consider doing so temporarily if there is concern of airborne disease in the building. Healthy and green building certification programs such as LEED and WELL recommend a minimum of MERV-13 filters. Buildings are often concerned about using high efficiency filters because they are expensive, become loaded faster and increase fan energy consumption. Cyclone has worked with dozens of buildings to replace standard box filters with high-efficiency v-bank filters which don’t become loaded faster and can reduce energy consumption.
If you have building occupants that are concerned about the quality of air, consider bringing more fresh air in. Often, we operate equipment at minimum outside air levels prescribed by a code or standard to save energy. Increasing fresh air to the building can provide for a healthier and more productive environment. The WELL Building Standard recommends maintaining indoor spaces over 500 square feet keep carbon dioxide (CO2) levels below 800 ppm (outside air is typically around 410 ppm.) A combination of high-efficiency filtration and ventilation is a good strategy for a healthy indoor environment. It doesn’t eliminate the risk of airborne disease spread, but does reduce the risk.
If you have concerns or tenants/residents are asking what you’re doing about the air quality and risk prevention of airborne disease transfer, consider implementing some of the measures I’ve discussed. While we’re deep in the current crisis, it’s now that we realize the benefits of being proactive. Major disease outbreaks will happen again. In the 21st century, there have already been several notable global disease outbreaks including SARS in 2004, H1N1 “swine flu” in 2009, MERS in 2012, Avian influenza A H5 “bird flu” in 2014, Zika virus in 2016 and now COVID-19. Being proactive means have an indoor air quality plan and emergency air quality action plan. If you’re interested in learning more about creating effective plans, please contact us at WorkWithUs@cyclone.energy or 312.945.8443. Finally, don’t panic. Follow CDC guidelines, practice social distancing and continue to wash your hands with soap for 20 seconds multiple times a day.