The world changed on March 11, 2020, when the World Health Organization declared COVID-19 a pandemic. Since then, the massive disruptions caused by the virus have left millions of people without work, and their normal lives have been transformed.
Everyone, it seems, is asking questions as to what needs to be done to stay safe and defeat this thing. Designers, builders, and those in the HVAC industry are no different. What they want to know is this: How does one keep COVID-19, and airborne viruses in general, out of facilities? There’s a lot about this virus that remains unknown. But ASHRAE, the Centers for Disease and Prevention (CDC), and the Environmental Protection Agency (EPA) all have guidance in regard to COVID-19. Healthcare, schools, single- and multi-family housing, offices, retail outlets, manufacturing plants, and public transportation are all at risk. And while there is no single solution to the problem, there is certainly a series of steps a building owner can take to ensure a higher level of indoor air quality.
Back to The Basics
First, it’s always good to go back to the basics, which is standard maintenance. If an HVAC system is equipped with the latest high-efficiency filters, it means little if the overall performance of the unit is poor. This means that the semi-annual inspection remains critical, even as the pandemic pushes us to look at HVAC systems in a new light.
Air systems seem to give out when they are needed most, especially when they are working hard during scorching heat or bone-chilling cold. To prevent failure, a good maintenance plan will include general upkeep, regular inspections of the gas supply and gas controls, air movers, condensate removal and disposal systems, thermostats, belts, filters, and electrical components. An exhaustive checklist, one augmented with boxes for COVID-19, is a must for property owners, facility managers, and contractors.
Filters and UV Lamps
In the age of COVID-19, many have asked about filtration. While filtration must certainly be part of any risk mitigation plan, filters alone will not be enough to keep the virus out of a building. So far, social distancing and good hygiene are still considered the best ways to keep indoor spaces safe. With filters, they must be designed for the building in which they are being used. Low-efficiency filters, those less than MERV-8, are unlikely to make a difference.
Minimum Efficiency Reporting Values (MERV) are used to report a filter’s ability to capture particles between 0.3 and 10 microns. A minimum MERV 13 filter will be needed to capture an airborne virus. A LEED-certified building will have been specified with MERV 13 filtration or better when designed. Ensure they are still in place and make sure the filter frame and gasketing are still in a good condition. But high-efficiency filters have their own issues. They are so good at capturing pollutants that they might need to be changed more often, and they could adversely affect the volume of air coming into an interior space. Also, when changing filters, keep in mind that they could be harboring active microbiological material. The technician should always wear PPE.
Properly designed UV lamps can also be effective, but if they are not aligned with the filtration, humidity control, and airflow management, they will not perform at their optimum level.
An aftermarket ionization can be a good solution to the sometimes-expensive filter upgrade. Easily installed in most HVAC equipment, the unit produces ions that purify air by eliminating airborne particulates and pathogens.
Carefully check the condensate drainage situation. Make sure the drain pan slopes in the right direction and that the P trap is clear. Also, make sure the dampers are working properly and that gaskets are in good shape. ASHRAE recommends that outside air units are run at 100% outside air.
During an inspection, it could be time to clean the energy-recovery wheel, something that could help the fight against COVD-19. The wheel can be removed and cleaned as needed, and a mild nonacid cleaner can be used, like a 3% mixture of hydrogen peroxide. EPA-registered cleaning agents are also advisable. Read the label and follow the instructions. However, do not bypass or disable the energy recovery system. This could result in negative outcomes such as reduced outdoor ventilation and changes in indoor humidity.
A key step to take early on is to make sure a building is pressurized so that it’s not pulling out more conditioned air than it’s putting in. Set the volume of the unit, the volume of the extraction and the exhaust and make sure that it’s maintained. At the design level, when it’s either new construction or a total remodel, building owners should consider installing an integrated HVAC system with an infection control package. But beware, an HVAC system has to be compatible with the facility or it will not function as hoped.
While many have asked about hospitals and what they use for indoor air quality, it might not be the right direction in which to look. Hospitals are unique in that they have specialized units that are maintained by dedicated staff, making hospitals different than retail buildings, schools, and office complexes.
With HVAC systems, it’s all about the flow. Increasing the amount of outdoor air coming into a building can help reduce the concentration of airborne contaminants inside. In a home, it could be as simple as opening a window or, if the home is equipped with one, turning on the attic fan. During maintenance with commercial systems, ensure that there are proper exhaust air recirculation rates. The proper term is Exhaust Air Transfer Ratio (EATR). The recommendation is to maintain a higher pressure in the supply air section than the exhaust air section. This should reduce the amount of EATR to 3% or less. Maintaining space humidity between 40-60% is also recommended.
For a building like a school that typically closes over the summer, it is recommended to operate the building for at least a week in occupied mode before returning it to use.
From where it stands right now, COVID-19 is going to be with us for a while. Even if the virus disappeared tomorrow, the lessons learned are too important to ignore. A pandemic can cause catastrophic damage to lives, economies, and to the very fabric of society. Can HVAC systems defeat a foe as formidable as a pandemic? The answer is no, at least not yet. But in the course of maintaining and improving those systems, and doing so with expert guidance, they can certainly contribute to better outcomes.
Richard Boothman is director of North American sales at Modine in Racine, WI. This is his first article for Facilities Manager.
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