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How to Make Indoor Air Safer in a Pandemic

How to Make Indoor Air Safer in a Pandemic

Posted: December 28, 2020 | Project Management

With the onslaught of winter and human habitation moving indoors, pandemic worries shift to how we can help provide clean indoor air in buildings to slow the spread of COVID-19.

DCD Magazine asked a series of questions to ASHRAE, who were kind enough to answer our request. The responses were provided by the ASHRAE Epidemic Task Force Team Leadership:

• Professor William Bahnfleth, chair of ASHRAE’s Epidemic Task Force
• Professor Max Sherman, residential team lead for ASHRAE’s Epidemic Task Force
• Luke Leung, commercial and retail team lead for ASHRAE’s Epidemic Task Force

DCD Magazine: Winter is here and people are gathering indoors. What are some simple things businesses can to curtail the spread of airborne COVID-19?

ASHRAE, Luke Leung: The first line of defense is what the public health professionals have been saying: limit the number of new people, social distance, sanitize, and wear masks. The long-range transmission of COVID can be further minimized by providing code-required ventilation this winter, putting high efficiency filters in your HVAC system and running it, and using portable air cleaners.

If possible, maintain an indoor environment at 40 – 60% relative humidity, and a slightly warmer temperature if not much penalty to energy. Avoid condensation indoors. Provide code-required outside air amount and MERV-13, or above, filters for the HVAC unit.

Consider local humidification and/or air cleaning, if there are vulnerable staff members or locations, and minimize time spent indoors.

Some HVAC units that are controlled from the thermostat will stop the fan bringing in outside air, and filtration when the thermostat temperature is satisfied. Consider running the fan if occupants are expected to have prolonged exposures to each other.

DCD Magazine: What are some of the inexpensive changes that small business owners could do, using their current HVAC systems in older buildings, to help reduce and limit the spread of COVID-19?

ASHRAE, Luke Leung: Where climate permits, open up to outside air. If the system cannot bring in code requiredoutside air or filtration, provide local air cleaners with HEPA filters.

DCD Magazine: What tips on airflow should architects consider in designing stores and restaurants of the future?

ASHRAE, Luke Leung: Bring the inside out — allow people to do more things outdoors; outdoor dining pods, meeting rooms, stores, etc.

Bring the outside in — allow more sunlight and outside air into the buildings, where appropriate.

Allow flexibility of space for social distancing, for indoor and outdoor dining and events.

Material matters — There are new materials identified as being friendlier to humans than viruses that could be specified in buildings to make them safer.

Measured office — It would be helpful to provide technology to measure and inform occupants of temperature, density, etc. This will help assure occupants the building is working to keep them safe from the spread of disease.

DCD Magazine: What technology is already available that can easily be put to use to make indoor spaces safer during this winter?

ASHRAE, Bill Bahnfleth: The first thing an owner/operator should do is verify that their system is providingat least the minimum outdoor air required by applicable standards, such as ASHRAE Standard 62.1.

In addition, filters that treat recirculated indoor air should be upgraded to MERV 13 if possible. In some buildings, the combination of minimum outdoor air and MERV 13 filtration may be sufficient to provide the 4 – 6 air changes per hour of uncontaminated air that are recommended by a number of researchers.

If minimum outdoor air flow and filtration of air recirculated by HVAC systems is not sufficient to reach this range, good options are standalone HEPA filtration units and other air cleaners that remove particles efficiently, or air disinfection technologies like germicidal ultraviolet light.

Upper room UV-C systems, which must be applied room by room and can have a significant installation cost, have the best performance. Airstream disinfection by UV-C installed in air handling units is lower cost but produces lower uncontaminated air flow rates. If feasible, increasing outdoor air flow above minimum requirements is also an option.

DCD Magazine: Can you see new, inexpensive technological advances to clean indoor air of bacteria and viruses becoming available in the future?

ASHRAE, Bill Bahnfleth: There are many air cleaning technologies already in the marketplace that claim to be effective for inactivating or removing pathogens from the air. I think it is likely that some of these will be demonstrated to be both effective and safe.

One particularly promising technology is far UV-C disinfection. The far UV-C wavelength range, approximately 220 nm and smaller, is very effective as a disinfectant, and preliminary studies indicate that it is safe for human exposure. Other air cleaners that introduce reactive species — ions, hydrogen peroxide gas, hydroxyl radicals, and others — into the air may also become standard control technologies, but more research is needed to demonstrate their effectiveness and safety, and methods of test and certification programs are needed to ensure that these technologies are safely and effectively applied.

DCD Magazine: What is needed to establish national baselines for indoor air quality?

ASHRAE, Max Sherman: There are two senses of this question. The first is to know what typical Indoor Air Quality (IAQ), including contaminant levels, is correct to ensure buildings have acceptable indoor air quality. This is something that requires a lot of data. There is some data in the literature; the Department of Energy and other public institutions are trying to capture more data. There is not enough data to do this now, but as the price of sensors and data collection continues to go down we can look to this happening in the future.

The second sense is whether we can define operational contaminant limits to determine acceptable IAQ. This is something that ASHRAE is slowly working on, for example, with ASHRAE Standard 62 and the Indoor Air Quality Procedure. This effort is about determining typical contaminants of concern and acceptable levels.

DCD Magazine: How can ASHRAE help solve the COVID-19 crises?

ASHRAE, Bill Bahnfleth: Since April 2020, ASHRAE has been providing detailed technical guidance on HVAC related measures to reduce risk of airborne infection transmission in buildings. This guidance is under continuous revision as new research findings become available.

ASHRAE has been providing assistance to governmental and non-governmental organizations seeking advice onrisk management, and conducting numerous educational activities for those interested in reducing risk of COVID-19 transmission in built environments.

DCD Magazine: What are some of the measures that anyone can use to reduce the spread of COVID-19 in their home during the holidays?

ASHRAE, Max Sherman: The first line of defense is what the public health professionals have been saying: limit the number of new people, social distance, sanitize, and wear masks. The long-range transmission of COVID can be further minimized by increasing ventilation rate, putting high efficiency filters in your HVAC system and running it, and using portable air cleaners. ASHRAE has guidance on all of these methods.

About ASHRAE: Founded in 1894, ASHRAE is a global professional society committed to serve humanity by advancing the arts and sciences of heating ventilation, air conditioning, refrigeration and their allied fields.

As an industry leader in research, standards writing, publishing, certification and continuing education, ASHRAE and its members are dedicated to promoting a healthy and sustainable built environment for all, through strategic partnerships with organizations in the HVAC&R community and across related industries.

The Society is showcasing integrated building solutions and sustainability in action through the opening of the ASHRAE Global Headquarters building in metro-Atlanta, Georgia. The state-of-the-art, high-performing net zero-energy efficient global headquarters building is a destination venue for industry representatives, visiting from around the world, who are looking to experience cutting edge engineering and architectural interventions.

For more information and to stay up-to-date on ASHRAE, visit and connect on Instagram, LinkedIn, Facebook, Twitter and YouTube.