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Alameda County Health Care for the Homeless Toolkit for Improving Indoor Air Quality 2
Alameda County Health Care Services Agency
Colleen Chawla, Director
Nicholas Moss, MD MPH, Health Officer
HCSA Office of Homeless Care and Coordination
Kerry Abbott, Director
Lucy Kasdin, Director, Health Care for the Homeless Program
Alameda County Community Development Agency Healthy Homes Department
Larry Brooks, Director
Acknowledgements
March 13, 2023 revision
This toolkit was produced February 2023 by the Alameda County Health Care Services Agency’s Health
Care for the Homeless (ACHCH) program and Alameda County Community Development Agency’s Healthy
Homes Department.
Alameda County Health Care for the Homeless
1404 Franklin Street #200
Oakland CA 94601
510-891-8950
www.achch.org
Alameda County Health Care for the Homeless program is supported by the Health Resources and Services
Administration (HRSA) of the U.S. Department of Health and Human Services (HHS) as part of an award
totaling $4,064,392 and other non-federal funding sources. The contents are those of the author(s) and
do not necessarily represent the official views of, nor an endorsement, by HRSA, HHS, or the U.S.
Government. For more information, please visit www.HRSA.gov.
Writing and editing was provided by : Makda Woldesenbet, David Modersbach Alameda County Health
Care for the Homeless program; Ruben Briones, David Crosby, Alameda County Healthy Homes
Department; Review and Editing by: Debbie Shrem, Janelle Nystrom, Cassandra Marquez, Robert Stepp
California Department of Public Health; Liz Ortiz, City of Berkeley, Brett Singer Lawrence Berkeley Labs
ASHRAE, David Jacobs National Center for Healthy Housing ASHRAE; Aileen Mendoza, Alameda County
Environmental Health; Nicholas Moss MD, Kavita Trivedi MD Alameda County Public Health DCDCP.
Alameda County Health Care for the Homeless Toolkit for Improving Indoor Air Quality 3
Toolkit for Improving Indoor Air Quality in Homeless Shelters and
Congregate Settings
Who is this toolkit for?
This toolkit is intended for program managers, frontline staff, volunteers, and others who
operate homeless shelters, housing, or services in congregate settings. It includes strategies
that can help reduce the spread of airborne diseases such as COVID-19 and asthma triggers in
their facilities. This document does not supersede any other mandatory requirements.
Workplaces must continue to meet the requirements of Cal/OSHA ETS and all other local and
state directives regarding COVID-19. Please review CAL/OSHA requirements in the appendix.
Why does indoor air quality matter?
Improving indoor air quality (IAQ) is a key strategy to reduce the risk of spreading COVID-19 and
other airborne respiratory diseases like influenza, colds, and tuberculosis. Adequate ventilation
and filtration are important ways to improve IAQ. Increasing ventilation by mixing, filtering, and
diluting the air decreases the number of airborne germs that accumulate in shared spaces. This
will create a healthier and more protective environment for staff, residents, and visitors.
Improving Indoor Air Quality is just ONE part of creating a healthy environment!
We can work on multiple levels to create environments that reduce the spread of airborne
germs among residents and staff in homeless and other congregate settings. Some of the key
lessons we have learned during the COVID-19 pandemic will continue to be used now and into
the future:
• Screen for Symptoms: COVID and disease surveillance: Screening for symptoms,
provide isolation, know about emerging illnesses and responding to them.
• Mask Up: Wear a mask in congregate settings, especially among people who are
coughing.
• Make Space: Maintain appropriate physical distancing, reduce closely gathering people
together where possible.
• Test: Make COVID and other testing supplies free and readily available.
• Immunize: Encourage and support vaccinations: Flu, COVID and other immunizations.
• Get Treated: Get treated for COVID and other illness rapidly.
• Program Protocols: Have program-level protocols to prevent and respond to airborne
diseases.
• Ventilate: Use healthy strategies that mix, filter, and dilute the air in your facility.
This guide was developed 2/2023 by the Alameda County Health Care for the Homeless
program in collaboration with the Alameda County Healthy Homes Department. For updates
and information around homeless shelter environmental health resources, go to:
https://www.achch.org/environmentalhealth.html.
Alameda County Health Care for the Homeless Toolkit for Improving Indoor Air Quality 4
Table of contents
1. Key Concepts and Principles for Healthy Air
2. Glossary
3. How to Assess your Facility
4. Heating, Ventilation, & Air Condition (HVAC) Systems
5. Natural Ventilation
6. Portable Air Cleaners (PACs) with High Efficiency Particulate Air (HEPA)
filter
7. Other strategies/technologies & What Not to Do
8. Carbon Dioxide (C02) Monitors
9. Recommended Facility Policies and Procedures
10. Resources
Appendix 1: Bathrooms and Kitchens
Appendix 2: Congregate and Dining Areas
Appendix 3: Dormitories and Sleeping Areas
Appendix 4: Meeting, Group, and Interview Rooms
Appendix 5: Shelter-Based Isolation and Quarantine
Appendix 6: Responding to Air Quality Emergencies
Alameda County Health Care for the Homeless Toolkit for Improving Indoor Air Quality 5
Chapter 1
What Are the Key Principles of Healthy Air in a Facility?
A. Remove/Reduce Sources of Possible Airborne Infection
• Screen residents daily for symptoms of COVID/flu and isolate symptomatic
persons.
• Encourage everyone to wear a mask. Require masking for those who are
coughing/symptomatic.
• Encourage and support vaccination to reduce illness
B. Optimize Ventilation in Your Facility
• Mechanical Ventilation – Optimize your Heating Ventilation and Air Conditioning
(HVAC) systems through discussion with your HVAC maintenance staff, including
contractors. Ensure your system is balanced, pulls in as much fresh air as
possible, runs continuously when people are present, and maintained regularly
(including changing filters).
• Natural Ventilation: Open doors and windows to bring fresh air in when an
HVAC system is not available
• Remove Dirty Air: Keep clean air flowing in and dirty air flowing out
• Air exchanges per hour: Create the conditions to ensure at least 6 Air Exchanges
Per Hour in your facility – sometimes more if needed.
C. Optimize Air Filtration:
• Use portable air cleaners (PACs) with the highest particle removal efficiency such
as high efficiency particulate air (HEPA) filters to clean the air that is circulating in
a room and reduce possible transmission of airborne illnesses. Use portable air
cleaners that are the right size for your space and are approved by the California
Air Resources Board. Avoid ionizers or ozone generators
• Filters used in HVAC systems are MERV-13 grade or higher. MERV 13 is necessary
because it is far more effective at capturing small respiratory particles than any
of lower-rated. Higher rated (greater than 13) will provide only negligible
difference at greater costs and are best reserved for healthcare settings.
D. Roles and Responsibilities.
• Ensure that it is everyone’s responsibility to contribute to a healthy air
environment in your facility through clear procedures.
Alameda County Health Care for the Homeless Toolkit for Improving Indoor Air Quality 6
Chapter 2
Glossary
Airborne Transmission of Infectious Disease: When a person has COVID-19 or other diseases
such as the flu, they release small particles that contain viruses into the air when they breathe,
cough, talk, sing, or sneeze. Droplets and smaller particles or aerosols initially hover around an
infected person’s face— that’s why keeping a distance can help reduce infection. Aerosols can
also move like cigarette smoke and float in the air for hours. People nearby can become
infected with COVID-19 by breathing in enough virus particles.
Air Changes per Hour (ACH): approximates how many times per hour the “dirty” air is replaced
with “fresh” air in a room. ACH is a calculated value that allows standards, guidelines, and
comparisons for ventilation to be made for rooms of different dimensions and which have
different ventilation systems. We recommend getting at least 6 ACH in most shelter facilities,
through a combination of HVAC, natural air, and supplemental equipment such as commercial
exhaust fans and portable air cleaners (PAC) with HEPA filters.
ACH = CADR* (cubic feet per minute or cfm) × 60 (minutes per hour) ÷ room volume
(cubic feet).
For example, if your PAC has a CADR of 350 and your room volume is 6,000 cubic feet,
you will get 3.5 ACH solely through the PAC. You’ll need to add more PACs or other
approaches to get to 6.0 ACH.
Clean Air Delivery Rate (CADR)*:is a measurement, proven through rigorous testing, of a PAC’s
ability to remove pollutants. CADR is the most important metric for measuring PAC
performance. For COVID-19, look for the CADR rating for smoke. Calculate the CADR for the
room you plan to use a PAC with the following equation:
CADR = (ACH 6 x Room volume 6000 cubic feet)/60 minutes
For example, to achieve a recommended ACH of 6 for a room volume of 6,000 cubic
feet, you’ll need a PAC with CADR of 600 or more.
Central Air: Normally refers to a building’s cooling system. Central air usually utilizes air
conditioner that works to distribute cool air through a system of air ducts in a home or building.
CFM: Cubic Feet per Minute. Unit of measurement for CADR. .
Dilution: Dilution means both bringing in fresh air and removing stale air in a room; ventilation
that reduces the concentration of potentially infectious particles in a room.
Exhaust: Pushing or pulling excess moisture, stale air, and unwanted odors out of a particular
room or area. Exhaust fans are commonly found in restrooms and kitchens. Exhaust fans
should be uncovered with nothing blocking them at all times.
Fans: Portable, window, or in-line duct fans are used to create a current of air. Fans help to cool
and mix the air. Examples include ceiling fans, table fans, tower fans, stand fans, wall mounted
fans, or floor fans.
Alameda County Health Care for the Homeless Toolkit for Improving Indoor Air Quality 7
Filtration: Air filters which trap particles to remove them from the air. Some filters can trap
potentially infectious particles; some cannot. HVAC systems have MERV-rated filters in them,
and portable air cleaners should contain HEPA filters.
Forced Air: Normally refers to a heating system and usually utilizes a furnace or heat pump and
vents to deliver temperature-controlled air into rooms. Forced air systems frequently re-heat
and recirculate air back into rooms.
High Efficiency Particulate Air (HEPA) Filter: An air filter that can remove at least 99.97% of
dust, pollen, mold, bacteria, virus, and any airborne particles with a size of 0.3 micron (µm).
When HEPA filters become clogged, they no longer filter air properly and must be replaced.
HVAC (Heating, Ventilation, and Air Conditioning): HVAC refers to the different technologies
used for moving air between indoor and outdoor areas, along with heating and cooling both
residential and commercial buildings, usually with ducting, furnaces, and air conditioners.
Minimum Efficiency Reporting Value (MERV): All HVAC systems will have built-in, replaceable
air filters. MERV refers to the ability of these air filters to filter and capture particles with 1
being the lowest level of filtration and 20 the highest. Air filters for most business or residential
systems have a MERV rating between MERV 5 and 13. MERV 13 filtration is efficient at
capturing airborne viruses and should be the target minimum level of filtration.
Negative Pressure/Positive Pressure: The term “negative pressure” is used to indicate that air
is flowing into a room and out through an exhaust route (fan in window, bathroom exhaust fan,
etc.) “Positive pressure” would be when air is flowing outward from a room into the rest of a
facility, which we want to avoid in isolation rooms.
Natural ventilation: Airflow through windows and/or doors.
Outdoor air: Clean air drawn from outside the building either by natural or mechanical
ventilation. Also referred to as “fresh air."
Portable Air Cleaners (PACs): A device for cleaning indoor air.
Recirculated Air: Air that has been drawn from the inside of the building, passed through filters,
conditioned, and reintroduced into the building.
Room Volume: The quantity of air in a room. Calculate by multiplying length x width x ceiling
height in feet. For example: length 30’ x width 20’ x ceiling height 10’ = 6,000 cubic feet.
Alameda County Health Care for the Homeless Toolkit for Improving Indoor Air Quality 8
Chapter 3
How to Assess Your Facility for Ventilation and Risk of Airborne
Transmission
A first step is to assess your building. How you assess a building is going to be different based
on your role and responsibilities at the facility:
• Building Owner
• Facility/Maintenance Technician
• Program Funder
• Program Lead/Managers
• Program Frontline Staff
• Program Participants/Residents
Based on these roles, there may be different responsibilities connected to developing and
maintaining a safe and healthy indoor air environment:
Program Role Responsibilities
•
ventilation, heat systems.
• Invest in upgrades.
• Ensure that all systems meet local codes.
•
• Maintain adequate mechanical and natural ventilation.
•
practices, as part of contract deliverables.
• Negotiate with building owners for facility upgrades.
• Develop and build in funding to pay for facility upgrades.
•
• Submit work request to address maintenance issues.
• Communicate desired ACH, outside air intake, system settings, and filter
ratings with HVAC/maintenance tech and contractor.
• Develop and maintain work procedures and practices to ensure healthy
air environments.
• Work with funders to identify and pay for facility upgrades.
•
• Ensure Portable Air Cleaners are operated correctly.
• Maintain adequate ventilation according to procedures (open windows,
fans, HVAC, filters) Request training and assessment.
• Review CO2 monitor.
• Report issues or participant feedback to program lead.
• Staff with direct contact to infectious persons (RN, etc)
•
• Raise ventilation issues to staff
Basic Questions to Guide Site Assessment
Your work will be to consider where to focus your attention, to identify the spaces that require
adjustments, know the sizes of each room, and determine activities to carry out at your facility.
Alameda County Health Care for the Homeless Toolkit for Improving Indoor Air Quality 9
Establish what assistance you would like: a walk-through inspection, technical assistance, or an
evaluation of your facility for program review. You might use the below information:
A. What are the uses of your facility?
a. Where do people congregate/spend time?
b. What rooms are used for what purposes?
B. Map your facility/floorplan – acquire or draw a floor plan of the main rooms, halls of
the facility – don’t forget to mark windows and doors.
C. Determine size (volume) of key rooms
a. When we talk about airspace for ventilation, we generally think in terms of cubic
feet. Cubic Feet = Length x width x ceiling height (all in feet).
b. Example: Dining/Congregate area of the facility is 30’ wide, 40’ long and has
ceiling height of 10’. The room volume to use in ventilation calculation is 30’ x 40’
x 10’ = 12,000 cubic feet.
D. Identify High Risk Areas of your Facilities
Which spaces have the most risk of catching COVID and other diseases through the
air? Consider the factors that help virus build up in the air and make it more likely
someone will breathe in enough virus to get sick. For example:
• Places where people aren’t wearing masks
• Crowded spaces, such as common areas – dining rooms or places where people
line up for items.
• People spend a long time together (such as sleeping areas, waiting rooms,
meeting rooms).
• Small rooms – also with low ceiling height.
• People are breathing hard (exercising) or singing – these activities mean people
are expelling more particles or aerosols into the air .
E. Observation
• How does air move through your facility? Consider walking around different
spaces with a burning stick of incense -- watch what happens to the smoke trails.
Does it linger/settle? Does it move out of the room quickly? Note how quickly
and pervasively others can smell the scent.
• You can also use a lightweight (down) feather to trace air currents.
• Where are potential sources of fresh air?
• How hard is your HVAC system blowing? Is it consistent, or automatic based on
temperature? Does your HVAC/ventilation system seem to recirculate stale air?
• Attach light pieces of ribbon or tissue to ventilation supply vents to verify how a
system is working.
F. What are your facility-based processes for addressing IAQ issues?
a. Maintenance: How often are systems inspected? Cleaned?
Alameda County Health Care for the Homeless Toolkit for Improving Indoor Air Quality 10
b. How are issues or problems addressed?
c. What is the chain of command/reporting/response structure?
G. Annual Healthy Building Checkup for your building
Make it a policy to regularly carry out a building “checkup.” This could be done by a
contractor or carried out by staff. Use this checklist and check this helpful resource for
HVAC and ventilation systems.
a. Equipment
i. Yearly maintenance plan for HVAC including regular duct cleaning and
replacement of HVAC MERV filters.
ii. Windows operating, fans in working order and cleaned.
iii. Replace HEPA filters on Portable Air Cleaners.
iv. Ensure that portable air cleaners are appropriately located.
b. Identify activities and areas of the building that warrant special attention.
Examples:
i. Schedule building maintenance.
ii. Clean all rooms, especially those heavily in use.
iii. Assess places where mildew or mold might grow.
iv. Clear out junk and items no longer needed.
v. Determine if room utilization is changing. Establish ways to improve the
air quality if you have new gathering/waiting/interview/sleeping rooms?
H. Program Policies and Procedures:
Are staff and residents following program procedures that promote healthy air
environments?
Alameda County Health Care for the Homeless Toolkit for Improving Indoor Air Quality 11
Chapter 4
Heating, Ventilation, & Air Condition (HVAC) Systems
Heating, Ventilation, & Air Conditioning (HVAC)
Systems are mechanical, built-in ventilation,
heating and/or air conditioning systems. HVACs
help increase indoor air flow by 1) pulling in
outdoor air, 2) mixing the air, and 3) filtering both
recirculated and outdoor air entering the system.
If your building has an HVAC system, follow this
checklist:
Note: It is recommended to consult with a
certified HVAC specialist, especially before
making any changes to your HVAC system.
Follow recommendations by the American
Society of Heating, Refrigerating and Air-
Conditioning Engineers (ASHRAE).
Make sure your HVAC system generates at least 6 air exchanges per hour (ACH). This
means that the HVAC system is replacing unhealthy air in a room at least 6 times every
hour with fresh outdoor air and/or filtered recirculated air. You can maximize Air
Exchanges/Hour through a combination of HVAC, natural air, and air filtration,
depending on the facility and circumstances (outside weather).
Run the HVAC system 24/7 IF the space is always OCCUPIED. If the space is only
occupied for specific hours, run the HVAC system during occupancy and a minimum of 2
hours before and after occupancy of the site. To make sure the system runs
continuously, Disable demand-control ventilation (DCV) controls on the system’s
thermostat. DCV adjusts ventilation based on occupancy or temperature. Disabling DCV
controls will allow the system to operate continuously regardless of temperature or
occupancy. However, you might not want to do this during a smoke or air quality
emergency.
Maintain indoor comfort according to the design temperature and relative humidity.
According to the World Health Organization (WHO) guidance, avoid setting climate
control systems to “cold” low temperatures (below 70oF) and “dry” low humidity
settings (below 40%). ASHRAE recommends a maximum indoor relative humidity of
60%.
If outdoor air quality is safe (especially important during wildfires), increase the
setting on your HVAC system so that it intakes the maximum amount of outdoor air
Alameda County Health Care for the Homeless Toolkit for Improving Indoor Air Quality 12
possible (aim for 100%). Fully open outdoor air dampers and close recirculation
dampers to reduce or eliminate air recirculation.
Generate airflow in the direction of clean air to less-clean air: In other words, supply
filtered/fresh air to spaces with residents, and remove air from spaces with potentially
infectious occupants.
Use the highest MERV-rated filter that your HVAC system can handle. Install at least
MERV-13 filters as they can capture airborne particles such as COVID-19. Some HVAC
systems may not be able to handle a minimum of MERV-13 filters. Consult with a
professional before upgrading your filters.
Follow the manufacturer’s recommendations and talk with a HVAC specialist to
determine how often to change the HVAC filters. When visually inspecting HVAC filters
on your own, always wear a fitted N-95 mask, eye protection, and disposable gloves.
Look to see if the filter is thickly coated with dust. That is a good indication that the filter
needs to be changed. Frequency may change after events such as wildfires, and for
filters located near kitchen exhaust.
Have a HVAC specialist inspect your HVAC systems regularly – at least annually,
preferably twice a year, for hot and cold seasons. Make repairs quickly to prevent
serious issues.
See below for questions to ask a HVAC specialist:
Alameda County Health Care for the Homeless Toolkit for Improving Indoor Air Quality 13
QUESTIONS TO ASK AN HVAC SPECIALIST REGARDING FORCED-AIR SYSTEMS
Ideally your HVAC will use MERV 13 filters or higher (14, 15, etc.) (3M or
Home Depot brand).
MERV 13 filter?
If yes, discuss upgrading your filters to MERV 13.
If no, ask "What is the maximum pressure drop for the required airflow?"
If you can’t use MERV 13, get the highest MERV recommended. Discuss
upgrading your HVAC system or taking other precautions such as
How often do I need to change my
filters?
Your HVAC specialist should know how often to replace filters or describe
what a dirty filter that needs replacing looks like. Ask for a filter
How often should I clean or inspect my HVAC system? At a minimum, your system should be inspected, serviced, and cleaned once a year. Inspection schedules will depend on type and use of the
building. If a system has both heating and cooling functions, heating
Does airflow in my building bring
clean/fresh air to the most
vulnerable people and exhaust
potentially infectious air away from
people?
Remember you want to avoid air flowing from isolation rooms or crowded
areas into other rooms with people. Your HVAC specialist or another
expert, such as an industrial hygienist, can assess the flow of air in a
building using special tools. For example, if a facility has an isolation
room for sick patients, the specialist can determine if HVAC system
changes can prevent air from moving from that space to other areas.
Remember that the direction of air flow may change over time, especially
How do I know my HVAC system is
working well?
HVAC specialists assess how well the system is functioning during their
regularly scheduled inspections. Ask how the HVAC responds to pressure
This table is from Improving Indoor Air - King County https://kingcounty.gov/depts/health/covid-19/ventilation.aspx
Alameda County Health Care for the Homeless Toolkit for Improving Indoor Air Quality 14
Chapter 5
Natural Ventilation and Dilution
Your facility should work to bring in outside “fresh” air to
add to your forced-air HVAC system, increase dilution and
increase Air Exchanges per Hour (ACH) in your facility.
Remember you can maximize Air Exchanges/Hour through a
combination of HVAC, natural air, and air filtration,
depending on the facility and circumstances (number of
occupants, and outside weather).
The goal is to improve air exchange as much as possible.
During or after high occupancy, some facilities may run their
HVAC system AND open windows at the same time – natural
ventilation will increase Air Exchanges/Hour. Depending on
your HVAC system and the circumstances, this may be
effective, but may also serve to wear your HVAC system.
Whether you have an HVAC system or not, you can follow
the following tips to increase natural ventilation:
Open windows and doors when it is safe, and
weather allows.
Use fans to increase the effectiveness of open
windows. A commercial exhaust fan is recommended to pull air up and blow air directly
outside. Meanwhile, leave other windows and doors open--ideally on the opposite side
of the room. This will help promote directional air flow where stale air from inside the
room will move outside. Try to position fans so that the air does not flow from one
person to another. Avoid using ceiling fans unless it can be adjusted so that the blades
are rotating in a direction that draws air up toward the ceiling rather than down onto
occupants.
Reduce occupancy and use of areas
where outdoor ventilation cannot be
increased to the optimal amount.
Encourage spending more time outside
during the day and schedule activities in
different, more healthy locations.
Alameda County Health Care for the Homeless Toolkit for Improving Indoor Air Quality 15
Chapter 6
Portable Air Cleaners (PACs) with High Efficiency Particulate Air
(HEPA) filter
Below are the smaller and larger Portable Air Cleaners currently being distributed by ACHCH as part
of our BAAQMD Clean Air Centers program.
More info (specific to Alameda County): https://www.achch.org/environmentalhealth.html
Alen BreatheSmart 75i Air Purifier
Top Speed: 350 Cubic Feet Minute (CFM)
CADR: 347
Smarter HEPA Smart Air Blast
Top Speed: 1300 Cubic Feet Minute (CFM)
CADR: 1360
Portable Air Cleaners (PACs) with High Efficiency Particulate Air (HEPA) filters are a designed to
remove at least 99.97% of dust, pollen, mold, bacteria, and
any airborne particles with a size as small as 0.3 microns
(µm).
A portable air cleaner should be used constantly and at top
speed to help filter air. A PAC is especially useful in buildings
with inadequate HVAC systems, when a building is crowded,
during cold or extreme heat, and in air quality/smoke
emergencies when it is not feasible to rely on outside natural
air for ventilation.
Checklist for use and maintenance of PACs
Place the PAC in areas where people may spend
the most time and/or where ventilation is poor.
Consider using multiple PACs in high-occupancy rooms.
Do not place PACs against walls, near furniture, curtains, or other objects that will block
the unit’s air intake and outlet.
PLACEMENT OF ORTABLE IR LEANER
Dirty air is pulled in from below and filtered
– be sure to have 4’ of clear
Alameda County Health Care for the Homeless Toolkit for Improving Indoor Air Quality 16
Make sure PAC is placed so the cord is not a tripping hazard or cover the cords.
Select the highest speed and leave the cleaner on for long periods of time.
Change the HEPA filters and carbon prefilters regularly! Follow the user manual for
maintenance needs, information on when to change the filter(s), and safety
recommendations to reduce hazards.
Checklist for choosing a PAC
It is important to choose a PAC that is appropriate for the size of the room.
In general, you want to ensure 6 Air Changes per Hour (ACH) in most rooms. ACH is
measured by how many times “dirty” air is removed from a room and replaced with
“clean” air in an hour. ACH can be achieved through a combination of HVAC, natural air,
and PAC.
Choose a PAC based on a clean air delivery rate (CADR) that is appropriate for the size
of the room. Purchase HEPA air cleaners that, when added together, create the
minimum CADR needed. Multiple units may be placed in the same space to achieve the
recommended CADR.
Choose a PAC with a CADR that will produce at least 6 air exchanges per hour (ACH)
for the size of your room, using the formula below:
1. Calculate Room Volume:
Room Volume = In cubic feet: length x width x height. Example: A room 20’
wide x 30’ wide and 10’ high has a volume of 6,000 cubic feet.
2. Determine How Much CADR you need to achieve 6 ACH:
𝐅𝐅𝐅𝐅𝐅𝐅𝐅𝐅𝐅𝐅𝐅𝐅𝐅𝐅: 𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑 𝐴𝐴𝐴𝐴𝐴𝐴 𝑥𝑥 𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅 𝑣𝑣𝑅𝑅𝑣𝑣𝑣𝑣𝑅𝑅𝑑𝑑(𝑐𝑐𝑣𝑣𝑐𝑐𝑑𝑑𝑐𝑐 𝑓𝑓𝑑𝑑𝑑𝑑𝑓𝑓)60 =𝐴𝐴𝐴𝐴𝐶𝐶𝑅𝑅
𝐄𝐄𝐄𝐄𝐅𝐅𝐅𝐅𝐄𝐄𝐅𝐅𝐄𝐄: 6 𝐴𝐴𝐴𝐴𝐴𝐴 𝑥𝑥 6000 𝑐𝑐𝑣𝑣𝑐𝑐𝑑𝑑𝑐𝑐 𝑓𝑓𝑑𝑑𝑑𝑑𝑓𝑓60 =600 𝐴𝐴𝐴𝐴𝐶𝐶𝑅𝑅
This means that a room with a volume of 6,000 cubic feet will need a PAC that
has a CADR of 600 -- OR multiple PACS that have smaller CADRs that will add
up to at least 600 -- to achieve 6 ACH.
3. Know the CADR of your Portable Air Cleaner (ACHCH’s Alen BreatheSmart 75i =
347 CADR; Smarter HEPA Smart Air Blast = 1360 CADR). Check the PAC and find
the “smoke” CADR specified by the manufacturer in the product description.
Use an online calculator to calculate your needs:
CADR Calculator: Clean Air Delivery Rate in CFM & m³/h
Alameda County Health Care for the Homeless Toolkit for Improving Indoor Air Quality 17
Having more than one PAC for a given space may be necessary. If possible, choose a unit
with either 1) a higher CADR than needed for the space or 2) use multiple units in the
same space to achieve the recommended CADR. These help to allow for effective
filtration using lower, quieter settings.
Choose a PAC that produces little to no ozone, as certified by the California Air
Resources Board (CARB).
Avoid PACs with additional technologies or features (e.g., ionization, plasma, UV lights,
and oil diffusers).
Use at the highest fan setting acceptable for the noise level (usually at or below 60
decibels).
In the above diagram, an functioning HVAC system with MERV 13 filter is filtering air,
replacing dirty air (black arrows) with filtered cleaner air (blue); windows are allowing
entrance of fresh air, exhaust fan is forcing stale air out, and Portable Air Filter is filtering and
cleaning air in the room
Alameda County Health Care for the Homeless Toolkit for Improving Indoor Air Quality 18
Chapter 7
Other strategies/technologies
Upper Room Ultraviolet Germicidal Irradiation (UVGI)
Upper room ultraviolet germicidal
irradiation (UVGI) systems can be
used to inactivate viruses in indoor air
in the upper part of the room. Upper
room UVGI systems are especially
valuable for spaces where ventilation
and air filtration are minimal or
nonexistent. UVGI systems have been recommended to reduce the transmission of
tuberculosis and COVID-19. However, these systems are extremely expensive and require
ongoing maintenance and engineering for installation.
o Consult with a UVGI specialist to determine if your space is a good fit for this
technology. More information: https://www.cdc.gov/coronavirus/2019-
ncov/community/ventilation/uvgi.html
What Not to do?
Fake Technology: Avoid air filters which are not HEPA filter based. These include many devices
that use ionization, plasma, photocatalytic oxidation, hydroxyl radical and other similar
approaches. Most of these air cleaners are not effective and some can release harmful by-
products. Check the California CARB webpage for certified Portable Air Cleaners and tips.
Plastic Barriers/Room Dividers/ Curtains: Partitions such as plastic barriers, room dividers and
curtains can be counter-productive: Partitions may restrict airflow and disrupt ventilation
patterns, trapping a greater amount of contaminated air on one side or the other. There is a
risk that partitions can trap virus-containing particles on one side or the other. Unless partitions
are ceiling to floor, without gaps, they do little to protect people, as particles that contain
viruses will find their way through small gaps. If partitions are in use, consider putting portable
air filters on both sides of the partition to reduce risk.
Avoid direct airflow between people: You should strategically place and use portable fans, air-
conditioning units, and ceiling fans to avoid creating strong airflow from one person directly to
another person. This is a particular concern in poorly ventilated environments.
Alameda County Health Care for the Homeless Toolkit for Improving Indoor Air Quality 19
Chapter 8
Carbon Dioxide (CO2) Sensors
Place CO2 monitors in congregate spaces to monitor air quality.
CO2 sensors measure the levels of carbon dioxide (CO2) that can build up indoors. CO2 levels
rise 1) when a lot of people exhale and 2) “dirty” air is not exiting or inadequate amounts of
fresh air are coming in. A monitor will show “green” when CO2 levels are low, “yellow” when
they are rising, and “red” when CO2 levels are at a more alarming level. These sensors are
visible to all room occupants.
The CO2 level of a room can be a proxy for poor ventilation. However, CO2 levels is NOT a proxy
for your risk of transmission of COVID. Also, high CO2 levels doesn’t mean there’s not enough
air to breathe. There are several factors that affect transmission risk including the number of
people infected in each space, proximity to infected people, masks, portable air cleaners, and
the other mitigation strategies.
How to use the CO2 sensors: o Set up CO2 level ranges. Low: 450 ppm Medium: 625 ppm High: 800 ppm o Place CO2 sensors at a height that is relatively the same as the participants. Avoid
areas at or near windows, near an air vent, or within 2 meters of open flame or
portable air cleaners. o When CO2 levels are rising and reach 800ppm (high), try to reduce CO2 levels:
i. Open windows and doors
ii. Reduce occupancy
iii. Run HVAC system
iv. Increase outdoor air supply via HVAC system, if air quality permits o Reducing CO2 levels back to acceptable levels means that ventilation/fresher air
has improved o Remember that Portable Air Cleaners will filter out possible infectious particles,
however they don’t filter CO2.
Alameda County Health Care for the Homeless Toolkit for Improving Indoor Air Quality 20
Chapter 9
Recommended Policies and Procedures
1. Please evaluate CAL/OSHA COVID-19 Prevention Non-Emergency Regulations, and
ensure that your workplace is compliant with these requirements, including ventilation.
You can use their COVID-19 Model Written Program as a template for developing
workplace protocols.
2. Establish roles and responsibilities for maintaining adequate indoor air quality:
a. Who is responsible for communicating with staff and residents about the
importance of indoor air quality measures? It’s important to talk to residents;
for example, that:
• Ventilation might always be running, it might be a bit cooler than usual
(due to constantly flowing air), etc
• There might be additional noise from PACs and ventilation strategies
• PACs and fans must remain on when people are present
b. Who is responsible for ensuring the HVAC system is operating continuously,
doors/windows are open, portable air cleaners are on, for maintaining
equipment logs, setting up regular maintenance, etc.?
3. Maintain up-to-date logs of equipment such as HVAC, portable air cleaners, filters and
their maintenance schedules (and where the replacements are stored) -- identify staff
roles for making sure these logs are kept up to date.
4. Make sure your HVAC system is regularly maintained by an HVAC professional.
5. Have an HVAC specialist determine the highest Minimum Efficiency Reporting Value or
MERV for the filters that your HVAC system can handle. Use a minimum MERV of 13 or
higher IF POSSIBLE.
6. Aim for a minimum of 6 ACH (Air Changes per Hour).
7. Run the HVAC system continuously when the building is occupied.
8. Bring in as much outdoor air as possible by opening windows and doors, and setting
your HVAC system to bring in 100% outdoor air (if outdoor air quality and weather
permits)
9. Be sure to install and maintain Portable Air Cleaners for additional air filtration in
crowded or frequently-used locations.
10. Pay special attention to higher risk spaces such as congregate dining and sleeping areas
11. Make sure exhaust fans are operating smoothly, and uncovered, especially in kitchens
and bathrooms
12. Room air is changed over at least three times between appointments or groups
Alameda County Health Care for the Homeless Toolkit for Improving Indoor Air Quality 21
Chapter 10
Resources
1. CA Interim Guidance for Ventilation, Filtration, and Air Quality in Indoor Environments:
https://www.cdph.ca.gov/Programs/CID/DCDC/Pages/COVID-19/Interim-Guidance-for-Ventilation-
Filtration-and-Air-Quality-in-Indoor-Environments.aspx
2. CAL/OSHA COVID-19 Prevention Non-Emergency Regulations (2023):
https://www.dir.ca.gov/dosh/coronavirus/Non_Emergency_Regulations/
3. CAL/OSHA Aerosol Transmitted Diseases Standards (2020)
https://www.dir.ca.gov/dosh/dosh_publications/ATD-Guide.pdf 4. Reduce Transmission of COVID-10 Through Air Quality Improvement – A Community
Checklist: https://maphealth.ca/wp-content/uploads/Reducing-Transmission-of-COVID-19-
Through-Improvements-to-Indoor-Air-Quality_-A-checklist-for-Community-Spaces.pdf
5. CDC Ventilation in Buildings Guidance: https://www.cdc.gov/coronavirus/2019-
ncov/community/ventilation.html
6. CDC Homeless Services Providers Interim Guidance: https://www.cdc.gov/coronavirus/2019-
ncov/community/homeless-correctional-settings.html
7. CDC: NIOSH Building Ventilation:
https://www.cdc.gov/niosh/topics/indoorenv/buildingventilation.html
8. CDC Interactive Ventilation Tool: https://www.cdc.gov/coronavirus/2019-
ncov/prevent-getting-sick/interactive-ventilation-tool.html
9. American Industrial Hygiene Association: A Ventilation Checklist:
https://synergist.aiha.org/202012-a-ventilation-checklist
10. American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE)
Guidance for Building Operations During the COVID-19 Pandemic:
https://www.ashrae.org/file library/technical resources/ashrae
journal/2020journaldocuments/72-74_ieq_schoen.pdf https://www.ashrae.org/technical-
resources/filtration-and-disinfection-faq
11. EPA Clean Air in Buildings Challenge toolkit: https://www.epa.gov/indoor-air-quality-
iaq/clean-air-buildings-challenge
12. Improving Indoor Air - King County https://kingcounty.gov/depts/health/covid-19/ventilation.aspx
13. Indoor CO2 sensors for COVID-19 risk mitigation: Current guidance and limitations
https://ncceh.ca/documents/field-inquiry/indoor-co2-sensors-covid-19-risk-mitigation-current-guidance-
and
14. Ventilation Guidance Federation of European Heating, Ventilation and Air Conditioning
Associations https://www.rehva.eu/fileadmin/user_upload/REHVA_COVID-
19_guidance_document_V4.1_15042021.pdf
15. California Air Resources Board Certified Air Cleaning Devices: https://ww2.arb.ca.gov/list-
carb-certified-air-cleaning-devices
16. DIY Box Filters: https://cleanaircrew.org/box-fan-filters/
17. Alameda County Guide for On-Site Isolation & Quarantine for Unlicensed Group Living
Settings: https://covid-19.acgov.org/covid19-assets/docs/healthcare-guidance/guide-onsite-iq-
unlicensed-group-living-settings-2023.02.07.23.pdf
Alameda County Health Care for the Homeless Toolkit for Improving Indoor Air Quality 22
Appendix 1:
Bathrooms and Kitchens
Bathrooms and Kitchens may generate a higher load of airborne particles due to their size and
use.
Bathrooms/Restrooms
o Make sure bathroom exhaust fans are in good shape
and exhaust directly to the outside. If needed, work
with an HVAC professional to install new fans or
upgrade existing fans. If smells linger in the bathroom,
or escape out into the hallway, this may be one
indication that your bathroom exhaust fan is not
working well.
o Keep doors closed and leave exhaust fans on 24/7
o Leave bathroom windows open
o Stagger and schedule use of bathrooms by different groups of users. Let bathrooms
ventilate between uses to reduce airborne particles.
o Make sure the toilets have lids and advise people to shut toilet lids before flushing. In
rare instances, COVID-19 virus found in feces may become airborne when flushed.
o Encourage wearing masks when using the bathroom (except when showering or
performing hygiene activities).
o Portable Air Cleaners are not appropriate for use in bathrooms. They will clog up due
to the moisture in the air.
Kitchen and dining spaces
o Ensure face coverings are worn in the kitchen.
o Run kitchen exhaust hood/fans on high, any time the kitchen is in use. Check
that exhaust fans are working. Exhaust fans reduce cooking fumes that
contribute to poor air quality and aid in pulling in outdoor air.
Alameda County Health Care for the Homeless Toolkit for Improving Indoor Air Quality 23
Appendix 2:
Congregate and Dining Areas:
Dining rooms and other congregate gathering areas require special attention because the more
people there are in a space and the longer, they occupy that space, the higher the risk of
transmission of airborne diseases is. When there are many people using a specific room or area,
try to achieve extra air ventilation and cleaning – we recommend trying to achieve 8 air
changes per hour during times of high use. Below is a summary of what to consider practicing:
o Install a CO2 monitor where it is visible. The CO2 sensor is an indicator for how well
ventilation is in a space
o Try and reduce or arrange capacity to always allow for at least six feet of physical
distancing for all activities. This can be difficult for dining; but try to allow for at least 3
feet of distance between individuals who are dining.
o Consider staggering mealtimes, only allowing a certain amount of people at a time
o Encourage or require residents and staff to wear face masks whenever possible, before
and after eating and drinking.
o Work to “clean out the air” in the hours before and after mealtimes by increasing fresh
air flow through doors and windows and fans.
o Do not use ceiling fans. If you do, only operate them in reverse flow direction to draw
air upwards.
o Consider adding extra Portable Air Cleaners to a dining and congregate room during
times of high occupancy in order to increase air filtration.
Alameda County Health Care for the Homeless Toolkit for Improving Indoor Air Quality 24
Appendix 3:
Dormitory and Sleeping Areas
Sleeping rooms can range from single rooms to shared dorms sleeping twenty or more persons
at night. These rooms pose the highest risk for transmission of airborne illness and need a
careful review to create better air conditions. However, bedrooms and dorms also need to be
comfortable (noise, temperature) so people can sleep in a healthy way.
A goal is to try to get to eight (8) Air Changes per Hour when sleeping rooms are in use. This
can be done through the techniques below and outlined throughout this toolkit:
o Ensure your HVAC systems are operating correctly, and continuously. The HVAC system
should continue to run through the night.
o Use natural ventilation: Open windows or doors bringing fresh air in where possible,
depending on weather and safety conditions
o If the cold makes it difficult to leave windows open, consider safely securing window
fans or box fans (sealing the perimeter around the box fan) to blow air out of selected
windows.
o Increase air filtration using PACs
o Some PACs can be noisy at the maximum level. If it is too noisy, try using
multiple PACs at a lower fan setting so that maximum filtration is still achieved at
a lower noise level.
o Consider creating separate isolation/quarantine spaces/rooms for residents with
symptoms or who are new to the program.
o If residents are sharing sleeping spaces, make sure that resident’s faces are at least six
feet apart. Align beds so that clients can sleep head-to-toe instead of head-to-head.
o If a facility is carpeted, use a HEPA vacuum to reduce the amount of virus and asthma-
causing dander/dust particles that may re-enter the air while vacuuming.
Alameda County Health Care for the Homeless Toolkit for Improving Indoor Air Quality 25
Appendix 4:
Meeting Rooms & Interview Rooms
Many homeless services facilities have meeting rooms for group sessions, or one-on-one offices
where case management or counseling services may occur. These rooms might be considered
higher-risk spaces most in need of ventilation, filtration, and to be used only when appropriate
(ex: confidentiality, privacy). It is recommended to try and get to eight (8) Air Changes per Hour
in meeting and interview rooms.
To ensure a healthier air space for meeting and interview rooms, consider how long staff and
clients spend time together, and how many people are in the meeting room. Also, assess the
size of each room. Ceiling height makes a difference too, as a small space will allow virus to
build up faster in the air. Encourage clients and staff to wear masks. Source control (wearing a
well-fitted KN95 mask) will help protect everyone from becoming infected.
Additional tips:
• Open windows to the outside (weather and safety permitting).
• Open office doors: Keep doors to smaller offices always open.
• Portable Air Cleaners: Consider always running appropriately sized Portable Air
Cleaners.
• Clear the air between appointments or groups: For example, if a group of people is
using a dining or meeting room, change all the air in the room over at least three times
before the next group comes in. If you change the air over three times, at least 95 per
cent of contaminated air will be replaced with outside and/or filtered air by the time the
next group arrives.
Room air can be cleared using HVAC systems, portable air cleaners, open
windows/doors, or some combination of the three. Even if you have an optimized HVAC
system, opening windows and running portable air cleaners on their highest settings can
increase the room’s total air changes per hour and reduce the wait time between
groups.
If you have a PAC or an HVAC system that can provide 6 Air Changes/Hour, it will require
30 minutes to remove 95% of the stale air out of a room.
• If you don’t know the room’s total air changes per hour, use all your tools (HVAC
system, portable air cleaner, open windows/doors) to air the room out for as long as
possible between uses.
Alameda County Health Care for the Homeless Toolkit for Improving Indoor Air Quality 26
Appendix 5:
Shelter-Based Isolation & Quarantine Capacity for Symptomatic or
Sick Individuals
The Omicron COVID surge in January to February 2022 resulted in overwhelming numbers of
infections and rapid transmission of COVID within shelters across the country. The surge
overwhelmed most local homeless Isolation/Quarantine (I/Q) hotel systems, and many shelter
programs nationally were forced to “fend for themselves” to create emergency
isolation/quarantine spaces at their facilities.
As funding for COVID I/Q programs declines so does I&Q hotel capacity, and shelter providers
will need to develop capacity to shelter symptomatic persons on site. This includes planning for
“surge” events where they might have to provide COVID-19 isolation and quarantine in place.
Please refer also to this guide to on-site Isolation & Quarantine for unlicensed group living
settings.
On-Site Care for Symptomatic Residents
• Please closely review the California Department of Public Health Infection Control
Guidance for Clients in Congregate Shelters, Including Shelters for People Experiencing
Homelessness
• If the client has severe symptoms, arrange for immediate medical assessment and care.
Call 911 if you see a person with the following:
o Trouble breathing
o Persistent pain or pressure in chest
o Pale, gray, or blue-colored skin, lips, or nail beds, depending on skin tone
o New confusion or disorientation
• Require the use of N95 masks by staff, volunteers, and residents during times of high
levels of COVID transmission.
• Follow the CDC cleaning and disinfection guidelines for community facilities if someone
is sick.
• Clients with symptoms of COVID-19 should be moved to a private area of the facility for
isolation and be tested as soon as possible.
• If a resident or household infected COVID-19 can isolate/quarantine in their own private
room, they may do so and have meals delivered, and use either a private bath, or a
shared bath that is well-ventilated between uses.
• If infected clients cannot be housed separately, they may be isolated as a cohort in a
large and well-ventilated on- or off-site space with a separate bathroom and a door that
can be closed to other clients.
• Symptomatic clients who have not been diagnosed with COVID-19 should not be placed
with clients who test positive for COVID-19.
• Symptomatic clients should wear a surgical mask, KN/N95 mask if available, or other
well-fitted mask with multiple layers.
Alameda County Health Care for the Homeless Toolkit for Improving Indoor Air Quality 27
• Shared items used by infected/symptomatic clients should be cleaned thoroughly
before use by another client.
On-Site Isolation and Quarantine Rooms
Programs are also learning to develop their own ongoing capacity to provide isolation and/or
quarantine rooms/quarters on-site. Shelter-based I&Q rooms can:
• Enable newly arrived residents to live temporarily in a separate cohort until it is clear
they are not infectious.
• Provide special rooms where symptomatic individuals can quarantine away from the
general population.
• Enable COVID-positive persons to safely isolate-in-place during their contagious
isolation period.
Following are some basic guidelines in development of isolation/quarantine rooms in homeless
shelter programs.
• Specify certain rooms or dorms to be used as I&Q rooms.
• Make every effort to draw in ample quantities of fresh air from windows. Be aware that
using window fans to draw in additional fresh air may result in “positive pressure” that
pushes infectious air into other common spaces. It’s best to exhaust air from isolation
rooms into the outside where it won’t be recirculated..
• Isolation room airflow should bring clean air into an I/Q room with potentially infectious
individuals and must exhaust “dirty air” outside the building -- and not into spaces
shared by healthy individuals.
• The term “negative pressure” is used to indicate that the air is flowing into the room
and out through an exhaust route (fan in window, bathroom exhaust fan, etc.) “Positive
pressure” would be when the air is flowing from the room into the rest of the building,
which we want to avoid in isolation rooms.
• This may mean using window fans
to also force or exhaust “dirty air”
out of a room.
• Keep potentially infectious dirty
air from re-entering shared spaces
by using a negative air machine. A
negative air machine is a fan and
HEPA filter with a known airflow
rate and has its own duct that
filters and exhausts dirty air out
the window– this ensures that no
dirty air is reused. If the space has
its own bathroom, turn on the
exhaust fan. This air is exhausted
directly outside.
Alameda County Health Care for the Homeless Toolkit for Improving Indoor Air Quality 28
• Place HEPA Portable Air Cleaners in isolation rooms, and ensure that you can achieve at
least 8 Air Exchanges per Hour (ACH):
o 8 x length (feet) x width (feet) x height (feet) / 60 = minimum CFM for Portable
Air Cleaner (HEPA)
• Check with a HVAC specialist to create additional ventilation and filtration such as higher
MERV filter rating in I&Q rooms, and to ensure “dirty” air is not flowing from the I&Q
room to other habited spaces.
On-Site Isolation and Quarantine Guidance and Recommendations during a COVID Surge:
Advanced Level: Read the Alameda County Health Care for the Homeless/ACPHD working
document “Guidance and Recommendations for Providing Shelter Based Isolation and
Quarantine for Individuals Experiencing Homelessness in Alameda County” for examples of on-
site isolation and quarantine during a COVID surge.
Alameda County Health Care for the Homeless Toolkit for Improving Indoor Air Quality 29
Appendix 6:
Air Quality Emergencies
During certain emergencies, such as wildfires and power outages, normal procedures for
maintaining adequate indoor air quality may change substantially:
Wildfires
The smoke and other particles generated from wildfires
have the potential to reach indoor environments. In
times of dangerously high levels of smoke or particulate
matter, outside air isn’t “fresh air” anymore. You will
want to reduce the amount of outside air entering a
facility. To reduce the number of harmful particles
indoors, follow some of these tips:
1. Plan ahead: Have volunteers construct Corsi-
Rosenthal air cleaners ahead of time to have
ready.
2. Monitor your local air quality
a. Regional/Bay Area Wide: Air Now (EPA)
b. California Wildfires Smoke Forecasts:
California Smoke Information
3. Keep at-risk residents indoors, especially those
with breathing or heart conditions.
4. Consider creating a “clean room” especially for high-risk residents.
5. Keep outside windows and doors closed & sealed as much as possible.
6. Adjust your HVAC system so that outside air does not enter. Recirculate filtered air.
7. Use as many Portable Air Cleaners with HEPA filter as possible to filter recirculating air.
Use those extra Corsi-Rosenthal air cleaners.
8. Wear N95 masks when outside.
Power outages
Power outages that last for more than a few hours have the potential to affect indoor air
quality. Specifically, there is a risk of carbon monoxide poisoning if portable generators
powered by fuel are not used correctly. To avoid that, follow the tips provided by the
Environmental Protection Agency (EPA) outlined here:
1. Do not use portable generators powered by fuel indoors. Use them outside and
at least 20 feet from building. Consider using portable generators powered by
batteries or solar power.
2. Install CO2 monitors indoors