Heating, Ventilation and Air Conditioning Systems (HVAC) Coronavirus Frequently Asked Questions

COVID-19 prevention in the workplace involves the following critical elements outlined in the University’s COVID-19 Guidelines:

  • Physical distancing of at least 6 feet between people and reducing density of personnel in UH spaces.
  • Wearing face coverings to contain the wearer’s exhalations.
  • Staying home when you are sick and symptomatic.
  • Cleaning and disinfecting high touch surfaces.
  • Education, training and awareness.

Maintaining building utilities, including HVAC systems, to support safe occupancy is a supplemental effort to the university’s COVID-19 prevention measures.

Common questions

I’m concerned about COVID-19 and the air quality in my work area. How do I know my work area has adequate ventilation?

UH buildings are typically supplied with a percentage of outside air either via natural ventilation or mechanical fans, dependent on each building and system. Those systems are maintained to provide ventilation and thermal comfort as designed through the following activities:

  • Air filters are provided in buildings equipped with central heating, ventilation and air conditioning (HVAC) systems.
  • HVAC systems are set to maintain appropriate indoor temperatures as much as system designs allow, which minimizes thermal stresses on the body. Systems often do not have the capacity to increase outside air ventilation rates while still maintaining recommended indoor temperature ranges.
  • Nearly all UH Mānoa building HVAC systems have continued to operate normally during the pandemic period, even while buildings are unoccupied. The systems were not shut down due to decreased occupancy load, but may be temporarily shut down for regular or emergency maintenance unrelated to COVID-19.
  • There are some laboratory ventilation systems that operate continuously with 100 percent outside air supply that is not recirculated in the building and is exhausted directly to the outside.
  • In areas without central HVAC systems (such as those with unitary split or packaged a/c system or window air conditioning unit) and operable windows are available, the system can be shut down and the operable windows opened. Keep in mind that this may impact the environmental condition of the space. Note, per UH COVID-19 Guidelines, “facilities where air conditioning is not utilized, campuses shall develop a protocol to increase circulation of outdoor air as much as possible, for example by opening windows and doors, except where doing so poses a safety or health risk (e.g., risk of falling, triggering asthma symptoms) to those using the facility or if it would compromise research.” Note: If portable fans are used to circulate air, caution should be used when locating the units to prevent the spread of respiratory particulates (e.g., do not place a fan close to one person’s face that will blow directly towards another person) and users must ensure safe electrical practices are in place.

What is being done to UH building HVAC systems given COVID-19?

The UH Facilities team is checking buildings with installed HVAC systems to ensure that they are operational, including but not limited to the following:

  • Fan systems are functional and operating.
  • Central HVAC fan filters are within acceptable operating ranges and replaced as necessary.

Can the building’s outdoor air ventilation rate be increased?

Some HVAC systems are designed to mix outside ventilation air with air recirculated from occupied spaces as required to comply with applicable energy codes. Many UH Mānoa systems do not have capacity to increase outside air ventilation rates while still maintaining recommended indoor temperature ranges.

Is the HVAC system designed to accommodate higher-rated filters?

HVAC filters are installed as originally designed, which can vary by building. Changing filters to a higher MERV rating is not planned at this time as they could decrease airflow capacity, thus affecting building pressures and temperatures.

How many air changes per hour are in my room?

Air changes per hour (ACH) is defined as the volume of ventilation air that is supplied and removed from the room every hour.

  • The ventilation air can be through natural or mechanical ventilation systems and helps to remove contaminants from a room.
  • The number of air changes per hour in each room in a building can vary throughout campus.
  • In general, laboratories are typically supplied with 6–12 air changes per hour, and office areas are typically supplied with 4–8 air changes per hour in accordance with the American Society of Heating, Refrigeration and Air-Conditioning Engineers (ASHRAE) guidelines.
  • If you notice evidence of inadequate air quality in your space (e.g., stuffy, stagnant) or thermal discomfort, please submit a request to the Work Coordination Center for evaluation.

Can my building’s supply airflow or exhaust airflow be increased or rebalanced?

HVAC supply and exhaust systems work in tandem to maintain building pressures that are close to neutral. While many systems do not have fan capacity to increase airflows, those adjustments can also cause uncomfortable drafts, increase noise from HVAC diffusers, increase internal space relative humidity, and create challenges for safe egress and security if exterior doors hold open due to imbalances in air pressure.

Should ultraviolet (UV) light systems be installed as a means to reduce virus transmission?

UVGI (ultraviolet germicidal irradiation) is only recommended by ASHRAE for HIGH RISK areas such as healthcare facilities, prisons and disaster shelters. It is not considered to be a cost-effective risk mitigation measure for LOW and MEDIUM risk areas classified based on OSHA’s Hazard Recognition Standard and are not recommended for general use as they can cause eye and skin irritation through inadvertent exposure or overexposure.

I have been reading a lot about air purifiers. Do I need an air purifier in my workspace?

While air purifiers may provide some additional protection from COVID-19*, they should not be used in lieu of other COVID-19 prevention measures. Generally, UH does not encourage the overall use of air purifiers as a means of preventing COVID-19 given the variable conditions and requirements of each space, as well as the varying specifications and usage requirements of each air purification device to be effective.

If a UH department chooses to purchase a unit at their own expense for departmentally assigned spaces, it is with the acknowledgement that an air purifier is not guaranteed to provide additional protection from COVID-19 and UH will not be responsible for evaluating spaces to determine whether an air purifier may provide additional protection from COVID-19. Any department considering such a purchase must submit a request to the Work Coordination Center to ensure there is adequate power for the equipment. The department will also be responsible for signing an Alteration Agreement, all costs associated with the equipment (including, but not limited to, maintenance, repair, removal, and service of the equipment), and assuring that the installation does not create unsafe working conditions.

*While the CDC has acknowledged that portable HEPA air cleaners can reduce exposure to simulated SARS-CoV-2 aerosols in indoor environments, especially when combined with universal masking, many factors including, but not limited to, whether the unit is equipped with a HEPA filter, the size of the room, the capacity of the air purifier, and the location of the air purifier and room occupants will ultimately determine how much or if an air purifier will provide additional protection from COVID-19.

What about ionization and ozone purifiers?

Ionization and ozone purifiers are also not generally recommended. Rigorous peer-reviewed scientific studies do not demonstrate their effectiveness, and many produce ozone which is an indoor pollutant with adverse health effects. In addition, ozone generators do not remove viruses and other pollutants at concentrations that are considered safe.

Will someone be monitoring changes in CDC and industry recommendations for managing HVAC / mechanical systems in response to the coronavirus pandemic?

UH Campus Operations and Facilities engineers, officials with the Environmental Health and Safety Office, and others will be conducting ongoing reviews of CDC recommendations, industry best practices and standards concerning the design, maintenance and operation of building heating, ventilation and air conditioning systems for the duration of the pandemic.

Who do I contact if I have additional questions?

Please contact your building coordinator or email covid19@hawaii.edu for any additional questions or concerns.

Resources and References

Acknowledgments

We would like to thank our peers at the University of Virginia, University of Washington and SUNY for their work that informed this FAQ guide, with release of responsibilities to their institutions for any information contained within.

Revised: August 26, 2020

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