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COVID-19 & Your HVAC System: Your Questions Answered


We know you have questions and concerns about the COVID-19 virus and operating/ maintaining your HVAC system. In this article, we’ll share the most accurate and up-to-date information available to help you make decisions.

The fact is, the COVID-19 crisis has developed so quickly that there has not yet been sufficient time for scientific studies to prove definitively whether the virus can be (or is likely to be) transmitted through an HVAC system. Much of the evidence that does exist is based on what is known about similar viruses.

Here’s a summary of what we can tell you with confidence at this time:

Let’s start with the good news: To date there is no conclusive proof that COVID-19 has been transmitted through a ducted HVAC system. The virus is transmitted primarily through direct contact with an infected person and to a lesser extent by touching a contaminated surface.

Experts say that airborne transmission of COVID-19 is theoretically possible, due to the ability of small droplets of virus particles to stay airborne for a period of hours under some conditions. It is presumed that some particles may stay airborne long enough to enter an air distribution system. However, experts believe that the risk of transmission this way is small.

There are mitigation tactics that can help to further reduce the possibility of your HVAC system becoming contaminated with the COVID-19 virus. It’s important to realize that these tactics must be part of a more comprehensive plan that includes preventing the primary means of COVID-19 transmission: person-to-person contact and contact with contaminated surfaces.

None of the mitigation tactics are foolproof. And some have significant disadvantages.

Here are answers to some of the specific questions we are hearing, as well as details about the protocols Arista is following to help keep everyone safe.

Can the virus be transmitted through HVAC ducts?

As we mentioned above, there is no definitive scientific conclusion yet as to the likelihood of COVID-19 transmission through air distribution systems.

That said, there are some potential mitigation strategies that you may be reading about. For example:

  • Using higher efficiency filters to trap virus particles.
  • Installing UV light technology or ionization-based air cleaners to destroy virus particles.
  • Increasing humidity levels to deactivate airborne particles.
  • Increasing ventilation to dilute virus particles.
  • Sanitizing air conditioning components before seasonal start up.

We’ll discuss each of these possibilities below.

Should we install higher efficiency filters to prevent spread of the virus?

High efficiency HVAC filters can capture small particles (such as viruses), and remove them from the airflow in your space. That’s why some are considering adding higher efficiency HVAC filters since they may reduce risk of COVID-19 transmission. But they can’t eliminate the risk entirely.

The problem is, the COVID-19 virus is so tiny. It’s possible that some particles may pass through even the highest efficiency filters.

It’s important to consider the operational impacts of using higher efficiency filters to your air conditioning system:

  • Higher efficiency filters are more dense and don’t allow as much air to penetrate. That leads to decreased air flow through your system. If you were already struggling with a system that wasn’t performing well, it’s likely your system will have even more trouble cooling your space.
  • Your system will also run longer as it struggles to achieve the set temperature, which uses more electricity and creates wear and tear on fans and other parts.
  • High efficiency filters trap more dust and debris and must be changed more frequently.

Another possible limitation is the setup of your system: it must be able to accommodate the size of the higher efficiency filters. The filters won’t help without proper installation.

Also, the cost of high efficiency filters can potentially be three times the cost, or more.

According to the National Air Filtration Association (NAFA)“In order for filters to have any impact on infectious disease transmission, transmission has to occur through the airborne route, filters have to be properly installed and maintained in appropriate systems to treat recirculated air, and filters have to be appropriately designed for the building in which they are used. More importantly, in most buildings and in most situations, filters may be considerably less effective than other infection control measures including social distancing, isolation of known cases, and hand-washing.”

Bottom line: if you’re thinking about adding high efficiency filters, call us to discuss your situation.

Does UV technology kill the COVID-19 virus?

UV systems use ultraviolet (UV-C) light to kill and deactivate microbes, including viruses, that may penetrate filters and get into HVAC systems. There are different types, including upper air and surface-cleaning UV disinfection systems.

According to ASHRAE (as reported in ACHRnews): “the germicidal wavelength can kill 90 percent of all microorganisms living on HVAC air ducts and evaporator coils, depending on wavelength intensity and length of exposure.”

However, it’s important to know that although this technology has been shown to be effective in killing other types of coronaviruses, it has not yet been proven to be effective on COVID-19.

Bottom line: You’ll need to weigh the cost of installing HVAC UV products versus the possible benefit, which is not guaranteed.

Should we consider other indoor air cleaning technologies, such as ionizers?

We have had customers ask about installing air cleaning products that use ionized hydrogen peroxide to destroy microbes in the air that passes through a ducted HVAC system. These small units can be placed within your air distribution system just past the filters, to destroy any particles that manage to penetrate your filters.

There is some evidence that ionizers can destroy coronavirus particles, so it may be an option worth considering if your system can accommodate the equipment.

guide to HVAC strategies for COVID

Bottom line: If you’re interested in ionization technology, give us a call to find out if it may offer some benefit for your system.

How do humidity and ventilation affect COVID-19?

Recent research has shown that increasing indoor humidity levels can help to deactivate the virus.

During the winter months when our spaces are closed up and heated, humidity levels tend to drop to extremely low levels (between 20 and 40 percent). Unfortunately, those are the ideal conditions for the COVID-19 virus to thrive and remain viable for longer periods.

According to the research, adding moisture to the air may damage the outer membrane of the virus, and also make “droplets” less likely to linger in the air. Increased humidity has the added benefit of moisturizing our mucous membranes, which increases your body’s ability to fight the virus.

That said, it’s important to avoid adding too much humidity to a space, because that can cause damage to furnishings and finishes (especially woodwork and fine art).

Humidification technology can boost humidity in your space to optimum levels. Be sure to consult with an HVAC expert to determine the optimum level for your space.

ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers) also recommends increasing ventilation (adding more outside air) to dilute any particles that may be present. Here in New York City, that’s not always easily done if you can’t just open a window. However, there are HVAC solutions that can add more outside air to your space.

Bottom line: It’s smart to have your indoor air quality evaluated and consider humidification and added ventilation. Arista can help with that.

Should my HVAC equipment be cleaned and sanitized?

Some of our customers are asking us to clean and sanitize system components prior to starting up their air conditioning systems.

We can’t be sure if any COVID-19 particles have remained viable in your system during the lockdown. Yet even beyond eliminating virus particles, there is certainly a benefit to cleaning condenser coils (which is normally done during a PM visit) and possibly your ductwork and other system components. Cleaning your system makes it operate more efficiently, consume less power, and keeps parts in good condition.

If you want additional peace of mind (especially if there have been confirmed cases of the virus in your space), Arista will be offering an HVAC deep clean and sanitization of evaporator coils, ductwork, and other system components where virus particles might be present.

For commercial systems, the ideal time to do this work is BEFORE you bring your employees back to work in your place of business and turn on the air conditioning system. However, you’ll need to make sure access to your space and equipment is available.

Keep in mind that sanitization of system components is a one-time cleaning, and does not provide any long term protection against future exposure to the virus.

Sanitizing your equipment and air distribution system offers reliable benefits. If you’re interested in deep clean and sanitization of evaporator coils and ductwork, ask about that when you request your AC preventative maintenance appointment.

Click here to request your your AC system maintenance & startup

What health and safety protocols do Arista technicians follow when servicing HVAC and Refrigeration equipment?

Staying home if not feeling well. Arista technicians are very conscientious about protecting the health and safety of our clients, as well as their co-workers. They are urged to stay home when not feeling well. Arista promotes quarantining when determined necessary.

Wearing masks. Arista provides masks to every technician to protect both our clients’ spaces and the well-being of our team.

Wearing protective glasses. Glasses are provided to every Arista technician to both protect our clients space and the well-being of our team

Wearing gloves. Wearing disposable gloves (and changing them between jobs) is an important tactic to reduce contact with the virus on surfaces. The CDC recommends, “Wear disposable gloves when cleaning and disinfecting surfaces. Gloves should be discarded after each cleaning.” After completing each job, Arista technicians are taught to remove their gloves, dispose of them safely, and then wash their hands.

Wearing booties. Every Arista technician is equipped with booties to prevent bringing dirt and debris into our clients’ spaces.

Disinfecting areas in contact with our personnel. After working in your space, Arista technicians clean all surfaces they come into contact with, such as HVAC access and controls, with disinfectant.

Safely disposing of filters. While COVID-19 is smaller than most filters can stop, it makes sense that some virus particles might stick on the fibers as they travel through the filter. Therefore, Arista technicians place used filters in plastic bags and throw them away in your outside trash receptacles.