Venue ventilation for COVID-19

venue ventilation COVID-19 Attention, meeting planners! Safe meeting venue ventilation for COVID-19 is critical. As we start thinking about returning to in-person events, it’s crucial to check that venues are upgrading their HVAC systems to handle potentially virus-infused air.

There has been little public discussion on this important topic. In this post, I’ll explain why questions about venues’ HVAC safety should be at the top of your site visit checklist.

Before we start, I need to make clear I’m not an HVAC engineer. My (perhaps) relevant background is an ancient Ph.D. in high-energy particle physics, and two years spent exploring ventilation systems—specifically air-to-air heat exchangers—when I owned a solar manufacturing company in the 1980s.


Since the pandemic began, the science on COVID-19 transmission has evolved rapidly. Because early theories turned out to be inaccurate, current preventative measures are frequently misdirected. So I’ve included a short history of theories of COVID-19 transmission that shed light on the reasons we’ve underestimated the importance of ventilation in creating safe environments for indoor events.

Next, I’ve outlined what current research indicates venues and properties should be doing.

Finally, I’ve aired my concerns about how well venues and properties are responding to the safety concerns I’ve introduced.

A short history of theories of COVID-19 transmission

Initial focus on surface contamination

Early reports on SARS-CoV-2 virus transmission falsely concluded that surface contamination was a significant transmission vector.

“COVID-19 is transmitted via droplets and fomites during close unprotected contact between an infector and infectee. Airborne spread has not been reported for COVID-19 and it is not believed to be a major driver of transmission based on available evidence.” [Emphasis added]
Report of the WHO-China Joint Mission on Coronavirus Disease 2019 (COVID-19), February 2020

This led to an epidemic of another kind—regularly cleaning and disinfecting surfaces. Meeting industry venues that have remained open during the pandemic adopted cleaning and disinfecting everything in sight as a visible assurance that their venues were safe places to gather.

“By May, [2020] the WHO and health agencies around the world were recommending that people in ordinary community settings — houses, buses, churches, schools and shops — should clean and disinfect surfaces, especially those that are frequently touched. Disinfectant factories worked around the clock to keep up with heavy demand.”
COVID-19 rarely spreads through surfaces. So why are we still deep cleaning?, Dyani Lewis, Nature, January 2021

However, current research suggests that the risk of infection from touching a heavily contaminated surface is less than 5 in 10,000. This is considerably lower than current estimates for SARS-CoV-2 infection through aerosols.

Despite this information, the current GBAC STAR™ Facility Accreditation Program for Cleaning, Disinfection, and Infectious Disease Prevention Accreditation Handbook concentrates on cleaning and disinfecting surfaces. Venue ventilation for COVID-19 is barely mentioned. The International Association of Venue Managers (IAVM)’s Public Assembly Facilities Recovery Guide (October 2020) has a section on HVAC systems, but still provides much more detail about cleaning and disinfecting.

By the way, the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) recommends that cleaning activities be performed after hours, rather than during meetings because “Vacuuming, sweeping, curtain cleaning, brooms, could potentially re- suspend infectious particles.” [ASHRAE Epidemic Commercial Task Force recommendations, updated March, 2021, Page 10.]

Droplet transmission

After scientific consensus quickly moved to droplet transmission as a significant factor, face masks were strongly recommended, and mandated at most in-person meetings. However, there have been numerous reports of lax mask usage during F&B breaks and socials.

Social distancing was also recommended. Why? Because it was thought that the COVID-19 virus was mainly transmitted via large respiratory droplets that fall quickly. This belief is still popular and frequently cited today.

Airborne transmission

Unfortunately, the latest research now points to aerosol transmission of COVID-19 as a significant vector. Aerosols are small droplets and particles (formed when small droplets dry quickly in the airstream) that can remain suspended for many minutes to hours and travel far from the source on air currents. An excellent summary of this research is included in The Lancet‘s April 15, 2021 article: Ten scientific reasons in support of airborne transmission of SARS-CoV-2. Here’s the key introductory paragraph:

If an infectious virus spreads predominantly through large respiratory droplets that fall quickly, the key control measures are reducing direct contact, cleaning surfaces, physical barriers, physical distancing, use of masks within droplet distance, respiratory hygiene, and wearing high-grade protection only for so-called aerosol-generating health-care procedures. Such policies need not distinguish between indoors and outdoors, since a gravity-driven mechanism for transmission would be similar for both settings. But if an infectious virus is mainly airborne, an individual could potentially be infected when they inhale aerosols produced when an infected person exhales, speaks, shouts, sings, sneezes, or coughs. Reducing airborne transmission of virus requires measures to avoid inhalation of infectious aerosols, including ventilation, air filtration, reducing crowding and time spent indoors, use of masks whenever indoors, attention to mask quality and fit, and higher-grade protection for health-care staff and front-line workers. [Emphasis added.]

How to think about aerosols

You can think of COVID-19 aerosols as cigarette smoke, or the aroma from cooking food. Of course, aerosols diffuse over distance, which is why social distancing is still a good idea, and why transmission of COVID-19 outdoors is unlikely unless people are tightly packed together. Incidentally, this means that if you’re eating or drinking at a restaurant or bar and can smell the food of diners at a nearby table or the smells of cooking from the kitchen, you’re not in a safe situation as far as COVID-19 transmission is concerned.

Pre-pandemic building ventilation standards are inadequate for COVID-19

Interim guidance published by the California Department of Public Health, points out that standard building environments have not been engineered to control exposures to small aerosols of hazardous viruses, such as COVID-19:

“Our understanding of the role that the built environment plays in the transmission of COVID-19 is evolving; recent literature has clearly demonstrated small aerosols can be carried well beyond the six (6) foot physical radius and remain suspended in room air where they can be inhaled. With the possible exception of hospitals, healthcare facilities, and research facilities that employ exhaust hoods, existing ventilation requirements, such as those established in the California Building Code and Title 24, were not intended to control exposures to small aerosols of hazardous infectious agents such as COVID-19.” [Emphasis added]
—General Considerations extract from the Interim guidance for Ventilation, Filtration, and Air Quality in Indoor Environments, California Department of Public Health, February 21, 2021

The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) points out that many existing mechanical air filters will not remove enough levels of airborne COVID-19:

ASHRAE recommends that mechanical filter efficiency be at least MERV 13 and preferable MERV 14 or better to help mitigate the transmission of infectious aerosols. Many existing HVAC systems were designed and installed to operate using MERV 6 to MERV 8 filters. While MERV 13 and greater filters are better at removing particles in the 0.3 micron to 1 micron diameter size (the size of many virus particles) the higher efficiency does not come without a penalty. Higher efficiency filters may require greater air pressures to drive or force air through the filter. Care must be taken when increasing the filter efficiency in an HVAC system to verify that the capacity of the HVAC system is sufficient to accommodate the better filters without adversely affecting the system’s ability to maintain the owner’s required indoor temperature and humidity conditions and space pressure relationships.” [Emphasis added]
ASHRAE Epidemic Taskforce Building Readiness (updated March 16, 2021)

Updating HVAC systems is not plug and play

The above ASHRAE guidelines explain that you cannot simply swap existing filters with MERV 13 or better filters and pronounce your building “ready” to handle potentially COVID-19 infected people. Venues and properties will typically need to involve “licensed and certified professionals and companies that can perform the analysis, testing, design, construction, control programming, balancing, commissioning, maintenance and operation services required to make the adjustments and achieve the performance included in these recommendations.”

Major heating plant upgrades may be needed to create safe air quality for occupants.

Reopening unoccupied buildings

Finally, many properties and venues have been operating in low-occupancy mode for long periods. Reopening such buildings safely, even to pandemic-appropriate occupancy levels, can require several weeks of preparation for the HVAC plant and facility staff. Here is what the Centers for Disease Control and Prevention (CDC) recommends be done before resuming business operations:

  • Evaluate the building and its mechanical and life safety systems to determine if the building is ready for occupancy. Check for hazards associated with prolonged facility shutdown such as mold growth, rodents or pests, or issues with stagnant water systems, and take appropriate remedial actions.
  • Ensure that ventilation systems in your facility operate properly. For building heating, ventilation, and air conditioning (HVAC) systems that have been shut down or on setback, review new construction startup guidance provided in ASHRAE Standard 180-2018, Standard Practice for the Inspection and Maintenance of Commercial Building HVAC Systems.
  • Increase circulation of outdoor air as much as possible by opening windows and doors if possible, and using fans. Do not open windows and doors if doing so poses a safety or health risk for occupants, including children (e.g., a risk of falling or of breathing outdoor environmental contaminants such as carbon monoxide, molds, or pollens).
  • To minimize the risk of Legionnaires’ disease and other diseases associated with water, take steps to ensure that all water systems and features (e.g., sink faucets, drinking fountains, decorative fountains) and water-using devices (e.g., ice machines, cooling towers) are safe to use after a prolonged facility shutdown.

COVID-19 Employer Information for Office Buildings, CDC, updated April 7, 2021

What are meeting venues doing to create safe ventilation?

I’ve taken the time to write this article because I’m concerned about the lack of visible venue and property efforts to resolve the ventilation safety issues caused by COVID-19.

One the last couple of months, I’ve reached out to industry contacts and meeting professionals on social media, asking for examples of venues and properties that have implemented (or are implementing) ventilation upgrades that will satisfy recent interim comprehensive guidelines such as those published by ASHRAE and the California Department of Public Health.

To date, I have been informed of only one venue—a California hotel property that installed MERV 13 filters. If your venue has made or is making such upgrades, please let me know, either directly or via comments on this post.

Perhaps many venues are quietly making these changes. I hope that’s the case.

Perhaps some venues are ignoring the problem, hoping that, somehow, the COVID-19 pandemic will disappear, and they’ll be able to host in-person events without updating their HVAC plant. I doubt they’ll be so lucky.

Frankly, I’m surprised that those who actually have updated their venue ventilation for COVID-19, aren’t publicizing this as a competitive advantage. Our industry is yearning for the return of in-person meetings. Being able to say a property is compliant with current ventilation guidance seems like a great selling point. This article from the Washington Post (kindly shared with me by Joan Eisenstodt) exemplifies the kind of positive PR that’s possible.

After all, it’s clear that many smaller businesses have already taken the necessary steps to create safe ventilation in their buildings. My dentist and physical therapist, and my wife’s massage therapist have all created safe ventilation environments for their places of business, and they’re happy to share the details with anyone who asks.

Is it too much to ask meeting venues to do the same?

More resources

Here are some additional resources that you may find useful. Again, please be cautious of any information you find that has not been published or updated in the last few months—it may be outdated.

Thank you

Many thanks to Joan Eisenstodt, Robert Carey, Anne Carey, Barbara McManus, Paul Radde, Dan Cormany, Sarah Diem, and Lauren Siring, who provided information and helpful suggestions and resources as I found my way into the complex topic of venue ventilation for COVID-19!

This April 2021 article includes information I’ve compiled from a variety of current sources. I’ve surely missed some valuable information. Please help me improve and update what I’ve shared via your comments below. Thank you!

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4 thoughts on “Venue ventilation for COVID-19

  1. This is not just happeing in US is happening around the World. The venues are not taking care about the air, all their safety protocols are based for surfaces and against the aersols, just following the social distancing.

    1. Thanks for your global perspective, Salvador. I’ve concentrated on the U.S. in the article, but I’m not surprised that the same “safety theater” cleaning protocols are being emphasized around the world, rather than the more important ventilation upgrades that are clearly needed.

  2. From an April 24, 2021 New York Times article: “Have You Satisfied Your Covid Compliance Officer?”

    ‘Dr. Adamson met some resistance when she recommended allocating a $30,000 budget to upgrade the filtration and HVAC ventilation at a Broadway theater rather than hiring staff to provide temperature checks at the door and constant cleaning of surfaces. “Choice A gives the appearance of doing the right things,” she said, referring to the door checkers and wipe-downs. “Choice B is actually going to mitigate risk.”’

    HT to Sue Pelletier for spotting this!

  3. Finally, the CDC acknowledges (May 7, 2021) that airborne aerosol transmission, which can occur over distances far longer than six feet, is a significant way that COVID-19 spreads:

    “The smallest very fine droplets, and aerosol particles formed when these fine droplets rapidly dry, are small enough that they can remain suspended in the air for minutes to hours.”

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