COVID-19 VENTILATION FAQS

Updated July 9, 2021

Limiting COVID-19 transmission in the workplace involves critical elements outlined in the
University’s COVID-19 Prevention Plan for the Workplace.
Maintaining building systems, including central heating, ventilation, and air conditioning
(HVAC) systems, to support safe occupancy is a supplemental effort to the University’s
COVID-19 prevention measures.
This document contains responses to frequently asked questions from occupants in
University facilities. Building coordinators and facility managers may share the responses
with occupants as appropriate.
Which standards and guidelines does the University follow for maintaining HVAC
systems?
• American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE)
o Coronavirus (COVID-19) Response Resources from ASHRAE and Others
• Centers for Disease Control and Prevention (CDC) – Ventilation in Buildings
• Seattle Mechanical Code / International Mechanical Code
• Washington State Department of Labor & Industries
o General Coronavirus Prevention Under Stay Home-Stay Healthy Order
o COVID-19 Guidance on Ventilation in the Workplace
What do I need to know about ventilation in University buildings?
UW buildings are typically supplied with a percentage of outside air either via mechanical
fans (a mechanical HVAC system), or natural ventilation (e.g., operable windows),
dependent on each building and system. Those systems are maintained to provide
ventilation and thermal comfort as designed through the following activities:
• In most cases, air filters in buildings equipped with central heating, ventilation,
and air conditioning (HVAC) systems are rated at MERV-13 or higher as
recommended by the CDC and have been inspected and changed per
maintenance procedures and schedules.
• Building HVAC systems have continued to operate normally during all phases of
the pandemic, even while buildings were unoccupied or at reduced occupancy.
• Laboratory ventilation systems operate continuously with 100% outside air
supply that is not recirculated in the building and is exhausted directly to the
outside.
• In naturally ventilated areas where windows serve as the main form of fresh air
supply, operable windows should be open while spaces are occupied.

July 9, 2021 | www.ehs.washington.edu | COVID-19 Ventilation FAQs | Page 1 of 5

 • In mechanically ventilated areas, operable windows may also be opened to
supplement mechanical ventilation when outside temperatures are moderate.
An exception where opening windows is not recommended includes
laboratories due to the potential interference with ventilation flow and pressure
balancing.
• In most cases, exhaust fans in restrooms operate continuously when buildings
are occupied. Some restrooms are equipped with a wall switch operated by the
occupant, in which case it’s suggested to keep toilet exhaust fans operating
continuously. For restroom exhaust fans to work best, it is recommended to
avoid opening operable windows in restrooms and keep restroom doors closed
(or mostly closed for single restrooms not in use).
• To ensure fresh air is supplied to spaces prior to employees arriving on site and
to ensure air changes occur after departure, building mechanical ventilation
system operating hours have been extended from 6 a.m. to 10 p.m. daily.
• Demand-control ventilation systems that increase or decrease outside air based
on carbon dioxide concentrations have been adjusted or disabled.
What is being done to verify building HVAC systems are operational, given COVID-19?
UW Facilities is checking HVAC systems to ensure that buildings are ready for reoccupation,
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.
• Fan filter racks are inspected for major gaps or damage.
• Outside air ventilation rates are being increased in recirculating HVAC systems
where possible.
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. While outside air
ventilation rates have been increased in many UW buildings, there are some systems that
do not have capacity to increase outside air ventilation rates while still maintaining
recommended indoor temperature ranges.
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 stale air
and contaminants from a room.
• The number of air changes per hour in each room in a building can vary
throughout campus and within a building.
July 9, 2021 | www.ehs.washington.edu | COVID-19 Ventilation FAQs | Page 2 of 5
 • If you notice evidence of inadequate air quality in your space (e.g., air seems
stuffy or stagnant) or thermal discomfort, please submit a request for evaluation
by campus location:
o On the Seattle campus, contact UW Facilities Customer Care Team at
careteam@uw.edu or submit an Online Work Order Request to main
campus UW Facilities.
o At UW Bothell, submit an Online Work Order Request to UW Bothell
Facilities Services.
o At UW Tacoma, submit an Online Work Order Request to UW Tacoma
Facilities Services.
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 some systems do have fan capacity to increase airflows, those
adjustments can also cause uncomfortable drafts, increase noise from HVAC diffusers, and
create challenges for safe egress and security if air pressure holds exterior doors open.
Other systems do not have fan capacity to increase airflows at all.
Can I use or purchase a portable air cleaner or air filter for my area? What kind of
portable air purifier should I purchase?
Yes. Individuals may use a portable air cleaner or air filter in their work area. When used
properly, portable air cleaners and air filters can help reduce the presence of airborne
particles. However, a portable air cleaner should not be solely relied on to prevent COVID-
19 transmission.
The portable air cleaner should:
• Be sized appropriately for the square footage where it will be placed.
• Be equipped with a high efficiency particulate air (HEPA) filter which is at least
99.97% efficient at capturing particles 0.3 micrometers (µm) in size.
• Be as quiet as possible to prevent interruptions in the work environment.
Units that purchase portable air cleaners or air filters should understand and follow
manufacturer instructions for use and maintenance for the specified model. The Portable
Air Cleaner Selection, Care and Maintenance Focus Sheet provides University units with
guidance for selecting and maintaining air cleaners for University spaces.
Can I turn on a portable air-conditioning unit or fan when it gets too hot?
• Yes, but the discharge airflow should be directed away from the body and face
of other people to prevent potential transmission to nearby individuals.
o Avoid the use of high-speed settings.
o Use ceiling fans at low velocity and potentially in reverse-flow direction
(so that air is pulled up toward the ceiling).
July 9, 2021 | www.ehs.washington.edu | COVID-19 Ventilation FAQs | Page 3 of 5
 o Direct the fan discharge towards an unoccupied corner and wall spaces
or up above the occupied zone.
• Fans can be used to improve room air mixing which helps distribute supplied
clean air and reduces the likelihood of stagnant air pockets where viral
concentrations can accumulate. This also limits the potential for SARS-CoV-2 viral
particles to accumulate in a portion of the room if an infectious person was
present.
• Follow all manufacturer instructions for use and maintenance for the specified
model.
Can carbon dioxide (CO2) monitors be used to indicate when there is good
ventilation?
According to the CDC, limited information exists regarding a direct link associating CO2
concentrations to a risk of COVID-19 transmission. Changes in CO2 concentrations can
indicate a change in room occupancy and be used to adjust the amount of outdoor air
delivered to a space. However, CO2 concentrations cannot predict who has a SARS-CoV-2
infection and might be spreading the virus, the amount of airborne viral particles produced
by infected people, or whether the HVAC system is effective in diluting and removing viral
concentrations near their point of generation.
Can ultraviolet lamps be installed within our building’s HVAC system or within
rooms?
According to CDC guidelines, ultraviolet germicidal irradiation (UVGI) should only be
considered as a supplemental technique to inactivate potential airborne viruses in the
upper-room air of spaces with insufficient or no mechanical HVAC system. Because
retrofitting current buildings with this technology is challenging and expensive, and there
are health and safety considerations with UVGI installations, these are specialized and
require careful evaluation by EH&S and facilities groups.
Should duct cleaning be performed and could it reduce transmission of SARS-CoV-2?
According to the EPA, duct cleaning has never been shown to actually prevent health
problems. A majority of the particles in air ducts adhere to duct surfaces and do not
necessarily enter spaces supplied by the HVAC system. EPA does not recommend routine
cleaning of air ducts. Ducts should only be cleaned in certain situations including rodent or
insect infestation, ducts clogged with dust and debris, or if substantial suspect visible mold
growth is present inside the ducts.
What if I have questions or suspect my HVAC system may not be working properly?
• To Report building HVAC issues by campus location, see below:
o On the Seattle campus, contact UW Facilities Customer Care Team at
careteam@uw.edu or submit an Online Work Order Request to main
campus UW Facilities.

July 9, 2021 | www.ehs.washington.edu | COVID-19 Ventilation FAQs | Page 4 of 5

 o At UW Bothell, submit an Online Work Order Request to UW Bothell
Facilities Services.
o At UW Tacoma, submit an Online Work Order Request to UW Tacoma
Facilities Services.
How are ventilation work orders prioritized?
UW Facilities and EH&S collaborate to prioritize ventilation work orders or requests for
information with consideration for ongoing campus operational issues in the following
order:
1. Clinical/Health care/COVID-19 research spaces
2. Lab spaces
3. Instructional spaces (with scheduled classes)
4. Office spaces
5. Support spaces
Resources
Centers for Disease Control and Prevention – Ventilation in Buildings
Environmental Protection Agency – Air Cleaners and Air Filters in the Home
OSHA - OSHA COVID-19 Guidance on Ventilation in the Workplace
UW – COVID-19 Prevention Plan for the Workplace

July 9, 2021 | www.ehs.washington.edu | COVID-19 Ventilation FAQs | Page 5 of 5