Can ventilation prevent the spread of Covid19? We have been hearing about how improving an HVAC system – in particular the ventilation – can prevent the spread of Covid19. It is often generalized that throwing money at the problem will stop the spread, that updating/replacing an HVAC system can render an indoor environment safe. If only it were true? The American Society of Heating, Refrigerating and Air-Conditioning Engineers, also known as ASHRAE, an often referred to authority and standard setter for all things HVAC, has summarized the situation in their “Position Document on Infectious Aerosols:” telling us under “PRACTICAL IMPLICATIONS FOR BUILDING OWNERS, OPERATORS, AND ENGINEERS” that:
“Even the most robust HVAC system cannot control all air flows and completely prevent dissemination of an infectious aerosol or disease transmission by droplets or aerosols. An HVAC system’s impact will depend on source location, strength of the source, distribution of the released aerosol, droplet size, air distribution, temperature, relative humidity, and filtration. Furthermore, there are multiple modes and circumstances under which disease transmission occurs. Thus, strategies for prevention and risk mitigation require collaboration among designers, owners, operators, industrial hygienists, and infection prevention specialists…”
Are there practical measures? If it is not possible to avoid transmitting COVID19, are there some practical measures that can help mitigate the problem? There are several products out there with UV lights that can be either plugged in and place on the floor of a space, or are designed to be placed in ductwork. These can make sense in certain applications, but generally are application specific, like health care for example. If they are applied to general applications, like an office, there can be some benefit but no guarantees. If one reads the fine print on these products, there is usually a disclaimer releasing the manufacturer from responsibility. Also UV lights take an extended period of exposure to be effective, meaning there is no benefit for typical circulation types of traffic. Another possibility is to increase the MERV level of HVAC filters. This can have an impact on how an existing system functions or a new one is designed, so it is best to consult a professional before proceeding with any modifications. In the end there is still no substitute proper PPE.
So what can be done? Larry Anderson, HVAC blogger and Editor of HVACInformed.com, suggests what amounts to general good practice strategies: filter indoor air, supply clean outdoor air, and exhaust contaminates. He points to the aforementioned ASHRAE Position Document on Airborne Infectious Diseases which recommends that
“…owners, operators and engineers should collaborate with infection prevention specialists knowledgeable about transmission of infection in the community and the workplace and about strategies for prevention and risk mitigation.”
I would encourage any property owner or business, whether small or large, to read the entire document before proceeding with an HVAC improvement project, and further to work with a professional at finding the best solution according to their particular situation.
What about innovations? Recently a contractor brought up a product called “Phenomenal Aire.” It is a cold plasma generator that, when installed in an HVAC system uses ionization to “scrub” airborne particles. There appears to be much recommending this product, but not necessarily the type in general. ASHRAE is advising caution as ozone production is one side effect – there are others – of the ionization process and can be a problem. Further, since there is not yet a industry standard MOT (method of testing), they counsel anyone considering an installation to verify that the proposed product has, at least, been tested according to UL2998 which determines that harmful ozone is not a problem. By way of an update, as of 3/3/21 we have been in contact with the manufacturer’s representative for “Phenomenal Aire.” We are told that the Phenomenal Aire meets UL867 and has been submitted for testing according to UL2998. Although the test has been delayed because of a backlog caused by Covid19, it is expected to meet this standard.
And don’t forget? It is always a good idea to insure that an existing system is in good repair and operating according to manufacturers recommendations.