May 8, 2020

We understand that our customers have many questions and concerns regarding COVID-19 in direct relation to the operation and maintenance of their HVAC systems. We have compiled the best available evidence and knowledge to date & share it in an effort to spread awareness about the precautions available to help keep everyone safe. Due to the ever-changing information about the disease, we will update this page with any new evidence as it becomes available.

Due to the fact that this pandemic has advanced so rapidly, there has not been enough time to conduct scientific studies for definitive proof of COVID-19 and transmission via an HVAC system. The current evidence out there is based on what we already know about similar viruses.
DISCLAIMER: We are not medical experts nor do we claim to be. Please read the advice below as interim guidance; as the information is based off the best available evidence and knowledge to date. D.P. Wolff Inc excludes any liability for any direct, indirect, incidental damages or any other damages that would result from, or be connected with the use of the information presented in this document.


  • 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.
  • YES – there are MITIGATION TACTICS that can be utilized to help reduce the possibility of transmission of the virus through your HVAC system. Bearing in mind that these tactics must be part of a larger more comprehensive plan that includes preventative measures against the primary source of COVID-19 transmission; person to person contact and contact with contaminated surfaces.
  • NONE of the available mitigation tactics are foolproof, and each facility will have different needs based on the operation of their own individual HVAC systems.

The bottom line is that yes, there are mitigation strategies readily available to help reduce the chance of virus transmission via your HVAC system. These strategies should be implemented in direct coordination between facility managers and your HVAC contractor and based on the specific design and system requirements for your equipment.


How can HVAC help your business safely reopen after Coronavirus?

For both a healthy reopening of your business and to protect air quality in your facility going forward, here are some practical recommendations:

  • Upgrade to higher efficiency filters to trap virus particles. ASHRAE recommends MERV 13 or the highest achievable rating based on system operating parameters.
  • Utilize ionization-based air cleaners to destroy airborne and surface viruses.
  • Install UV light technology to destroy virus particles. High quality, high efficiency filters improve air quality tremendously, but can only affect particles of 1 micron or larger. UV germicidal lights can not only affect smaller particles but can also destroy the DNA of submicron microbes. Adding UV lights to your HVAC system can tremendously improve air quality.
  • Increase air supply and exhaust ventilation. This helps to remove virus particles out of the building and to remove released virus particles from surfaces. The general advice is to supply as much outside air as reasonably possible. Also, actively using operable windows can further boost ventilation.
  • Clean and Disinfect Evaporator Coils. Dust and debris are routinely trapped in the coils, and this can contain virus materials and contaminants.
  • No use of re-circulation. Virus particles in return ducts can also re-enter a building when centralized air handling units are equipped with re-circulation sectors. It is recommended to avoid central re-circulation during SARSCoV-2 episodes: close the re-circulation dampers (via the Building Management System or manually).

How can upgrading to higher efficiency filters prevent spread of the virus?

Research has also indicated that appropriate air filtration limits the pass-through of virus particles, which frequently hitch a ride on larger particles, into downstream areas. Indoor air contains the most contaminants as it is limited and has no space to escape, and air is recycled causing the infections to transmit. High efficiency HVAC filters can capture small particles (such as viruses), and remove them from the airflow in your space. A MERV rating is used to report the effectiveness of air filters. MERV is an abbreviation for Minimum Efficiency Reporting Value, and tells you on a scale of 1-16, how effectively your filter traps the small particles you don’t want circulating through your workplace. See image

It’s important to consider the operational impacts of using higher efficiency filters to your air conditioning system. If you’re using a filter with a MERV rating that’s not compatible with your system, inefficiency and high energy costs may be the result. If you are considering using a higher efficiency filter, call us to discuss what options will work best for your equipment needs.

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.”

Are ionization devices effective against viruses?

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. This device works by purifying the air moving through the HVAC system using patented technology called needle-point bi-polar ionization. The ions that are generated are safe and they remove small particulates, dust, allergens, VOC’s and odors from the building air. They also kill airborne and surface viruses, bacteria and mold.

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.

Does UV technology kill viruses?

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.

Should your HVAC equipment be cleaned and sanitized?

Cleaning your system makes it operate more efficiently, consume less power, and keeps parts in good condition. Dust and debris are routinely trapped in the coils, and this can contain virus materials and contaminants. In addition to routine maintenance inspections, we recommend disinfecting indoor evaporator coils with a spray on “no-rinse” EPA registered cleaner that kills viruses similar to COVID-19 on hard non-porous surfaces.

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

When should you schedule your HVAC preventative maintenance?

If you’re making plans to reopen, taking care of the spring inspection now is essential. 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.

If your company has partially or completely switched to remote work due to COVID-19, an HVAC inspection is more important than ever. Your data center and servers are working harder than ever so keeping them cool is essential. An HVAC inspection will help ensure continued, efficient service. It will also alert you to any pending problems so they can be addressed without any interruption of service. If your building or facility does need service or an upgrade, you can have it done before reopening to minimize any disruption. It also ensures that you have fresh air filters installed for that reopening.

D.P. Wolff, Inc.   l   143 Bedford Road   l   Katonah, NY 10536   l   (914) 767-0515   l   (914) 767-3596 fax   l   info@dpwolff.com
24-HOUR EMERGENCY SERVICE (914) 767-0515

D.P. Wolff, Inc.

143 Bedford Road

Katonah, NY 10536

(914) 767-0515

(914) 767-3596 fax



(914) 767-0515