COVID-19 & The HVAC Industry
Helping Building Owners Adjust to a New World
Covid-19 Spreading During Summer
As summer wanes and fall approaches there is apprehension that the lifecycle of Covid-19 and its impact on our world may only be entering into its “springtime”. With numbers of reported cases continuing to rise in many states, even those that continue to take relatively aggressive measures to combat the spread, we may be in for a difficult fall and winter. Since the March shutdown of most business across the country many businesses have been allowed to reopen with social distancing measures in place. Back in the spring, the near-term hope was that, as summer approached, Covid-19 might, to a large degree, “bake out of the system” or, in other words, the warm, sunny days of summer might tamp down the transmission of the virus. The Spanish Flu epidemic in 1918 followed that pattern with a spike in the winter/spring, a great retraction in the summer then a return by Thanksgiving.
So, why has Covid-19 not been “knocked back” in the hot summer months? Much about the virus is still to be learned but one theory is that our summer environments include spaces that are air conditioned and it is these indoor spaces that have created the environments ideal for transmission of the virus. Mid-day dining outdoors in Charleston or Jacksonville Fl in August may sound delightful to some but, for most, retreating to the cool interior spaces is the only option they’ll consider. Therein lies the problem. Not so many years ago smoking was allowed anytime anywhere. Today, smokers must retreat to the outdoor spaces to enjoy a smoke. The smoke that emanates from the cigarette is the same whether indoors or outdoors but it disperses much better in the out-of-doors and the impact on others is dramatically reduced. The same rules apply to Covid 19 transmission and hence why dining outdoors creates a safer environment.
Improving Indoor Air Quality for Safety is Complicated
So how do we make our indoor spaces safer? Improving Indoor Air Quality (IAQ) while also making buildings more energy efficient is an ongoing drive of the HVAC industry. But IAQ has never had a challenge quite like that which Covid-19 presents.
A COVID -19 cluster was tracked to a restaurant where the A/C was blowing so hard it is believed to have spread the coronavirus between tables. (See Case Study – Covid-19 Outbreak in Restaurant).
A recent article by Tribune News Service featured interviews with several professors from UNC-Chapel Hill and Duke University that have studied the virus and the three experts agreed that for interior spaces, it is critical to reduce the concentration of the airborne virus through good ventilation. The recommendation is for building managers to increase the amount of outside air introduced to buildings with the caveat that bringing in new air requires “more energy to heat and cool compared to recirculating the existing indoor air.” In reality, the problem is far greater than simply turning up the volume of outside air intake at the expense of a higher utility bill.
Tony Furst, MSEd, CPD, LEED AP is a senior application engineer with Armstrong Fluid Technologies which works mostly on the water side of watersource HVAC systems. Furst explains, “you can’t just turn up the volume of outside air in a typical installation as the equipment is just not capable of handling it. If you increase the volume of outside air from 10 percent to 90 percent then you’ve got exponentially increased demand on the watersource loop. The piping is not sized for that, the pumps are not sized for it and the coils reflect the disconnect. You just can’t make massive changes to the ratio of outside air without significant ramifications.”
As more is known about coronavirus the problem may become much more significant. In July over 200 scientists collaborated on an open letter to the WHO. This group of scientists argues that evidence is emerging that Covid 19 may be a virus that is airborne spread by the smallest droplets (Aerosols). This is significant. Mandatory mask wearing is primarily aimed at reducing large droplet transmission. Large droplet transmission, by its nature of being “large”, means that when an infected person coughs…or sings…or just speaks normally, large droplets become airborne. These large droplets fall out of the air relatively quickly. This is the reason for 6 foot social distancing. In most cases, the virus will fall out within that 6′ buffer zone. Large droplet transmission is different from a true airborne virus. An airborne illness is one that is aerosolized (like the SARS virus) and which can live on airborne particles as small as a piece of dust and be infectious for a significant amount of time and travel long distances…even after the infected person has left the room. These small “micro-droplets” .125 microns or 125 nanometers in size can remain suspended in air as aerosols for hours and traverse long distances.
The Role of the HVAC Industry
So, what role does the HVAC industry play in combatting Covid 19 as well as viruses that may come our way in the future?
Numerous third-party applications are available for HVAC systems that can impact the potential spread of Covid-19 through HVAC systems. Ultraviolet (UV) treatment of interior air holds much promise and was covered in our June/July issue. Other solutions also hold promise.
There is conflicting information in the marketplace about the effectiveness of HEPA filtration. The consensus is that HEPA filtration…simply replacing your customers standard HVAC filters with HEPA filters…is of limited value. The reasoning is that HEPA filters, according to manufacturers’ labeling, is effective for particles sized .3 microns and larger. Remember, the Covid 19 virus is .125 microns so you might deduce that it will slip through a filter that is designed for capturing only particles .3 microns and larger. But that may not be the whole story. (See story on page 10). A NASA Study indicates that HEPA filters can indeed capture partilces as small as the coronavirus. Jim Rosenthal is owner of filtration manufacturer,Tex-Air Filters, and past president of the National Air Filtration Association (NAFA). He notes that the equation is more complex than that. He argues that HEPA filters don’t become “zero percent effective” once particles reach below .3 microns. In fact, according to Rosenthal, HEPA filters are still over 99 percent effective at removing particulate that is below .3 microns. If this is the case, then changing out customers standard filters for HEPA potentially is a relatively quick and easy measure to make buildings healther.
HVAC Equipment and Design
Even the best filters can’t improve air quality if the air doesn’t reach the filter. The number of recommended Air Changes Per Hour (ACH) varies widely depending upon how space is used and the number of people occupying that space. For commercial office space it is generally accepted that 4 ACH is the minimum air change rate acceptable. ASHRAE (American Society of Heating, Refrigeration, Air Conditioning Engineers) has established ASHRAE Standard 62.1-2016, “Ventilation for Acceptable Air Quality” which recommends a certain volume of air per occupant. For existing buildings, it generally falls to the HVAC contractor to initiate a discussion about the adequacy of existing systems.
The primary goal for HVAC contractors may be to help building owners achieve proper ACH in their buildings. A recent article published by Medscape quotes Jose-Luis Jimenez, PhD, an aerosol scientist, notes that solid science is emerging that supports aerosol transmission of SARS CoV-2 (the virus that causes COVID-19). His belief is that long-range aerosol-based transmission of the virus is not a major concern. He explains that the SARS-CoV-2 virus transmission is highest at close contact when concentrated aerosols are inhaled by individuals in close proximity but less likely on a room scale unless aerosols are allowed to build up in a room where ACH is low or there is crowding, singing and/or no masks. He also states that “We would expect that aerosols to have trouble infecting at very long range, such as through the ventilation system of a commercial building, owing to high dilution.”
If indeed, this is the case then an HVAC contractor’s primary focus should be helping building owners achieve proper airflow throughout every room in the building taking precautions to factor in all key elements including how many people will occupy a room and what activities those people will engage in within that room.
The new world we live in, a world that needs to continue to function in spite of Coronvirus, will require that the HVAC industry, with HVAC contractors at the forefront, take every opportunity to educate their customers about what constitutes a healthy building and being knowledgeable enough to facilitate those measures.
The new world we live in, a world that needs to contiunue to function in spite of Coronvirus, will require that the HVAC industry, with HVAC contractors at the forefront, take every opportunity to educate their customers about what constitutes a healthy building and being knowledgeable enough to facilitate those measures.
Other Articles in this Series
This article appeared as the feature story in the August / September 2020 print issue of Southern PHC. Featured alongside were Case Study: Covid-19 Associated with Air Conditioning in Restaurant and Understanding HEPA Air Filters and Covid-19.