Wildfire Smoke

smoky skies

Wildfire smoke is a mixture of gases and fine particles from burning trees and plants, buildings, and other material. The primary concern with exposure to wildfire smoke is that it contains fine solid particles (also known as particulate matter) that are 2.5 micrometers (PM2.5) in size or smaller. These tiny particles are harmful because they can reach deep into the lungs.

Breathing in wildfire smoke can produce harmful health effects, and can impact individuals with certain preexisting health conditions and those who are sensitive to air pollution.

Wildfire smoke may reach our UW campuses and satellite facilities from various areas both inside and outside of Washington state due to the increasing extent of area burned by wildfires each year.

Outdoor worker protections

The Wildfire Smoke emergency rule provides protection for personnel working outdoors for more than one hour who may be reasonably expected to be exposed to wildfire smoke.  The rule identifies two action levels to protect personnel when air quality worsens.

Air Quality Index (AQI) reaches 69

When the AQI is at 69 or higher in the location where outdoor work is occurring, the University is responsible for:

Air Quality Index (AQI) reaches 101

When the AQI is at 101 or higher in the location where outdoor work is occurring, University units must implement exposure controls where feasible. Such controls may include:

  • Providing work and/or rest areas in enclosed buildings, structures, or vehicles where the air is effectively filtered
  • Providing portable air cleaners in enclosed areas
  • Relocating work indoors or to an outdoor location with a lower AQI
  • Changing work schedules so that outdoor work can occur when the AQI is lower
  • Reducing the amount of work that involves physical exertion
  • Providing additional rest periods
  • Monitoring personnel for exposure symptoms; refer to the symptoms list in the frequently asked questions section of this page.

Respiratory Protection

When the AQI is at 101 or higher, the University unit must provide respirators at no cost to personnel exposed to wildfire smoke.

  • Respirators must be NIOSH-approved devices that effectively protect the wearers from inhalation of particles at the 2.5 micrometers (PM2.5) size, such as N95 filtering facepiece respirators (KN95 respirators not allowed).
  • Respirators shall be cleaned, stored, maintained, and replaced so that they do not present a health hazard to the user.

Air Quality Index (AQI) of 177

When PM 2.5 reaches 555 µg/m3 (Beyond AQI)

When the airborne concentration of PM2.5 is 555 or more micrograms of gaseous pollutant per cubic meter of ambient air (ug/m3), UW personnel must be enrolled in the respiratory protection program. Personnel must be provided and are required to wear one of the following respirators equipped with high efficiency particulate air filters:

  1. Loose-fitting powered air-purifying respirator; or
  2. Full-facepiece air-purifying respirator; or
  3. Full-facepiece powered air-purifying respirator; or
  4. Other respirators that are at least effective.

The following items do not provide adequate respiratory protection from wildfire smoke:

  • Surgical masks
  • Cloth face coverings
  • Bandanas
  • Scarves


The Wildfire Smoke emergency rule applies to UW work areas where it is reasonably anticipated that personnel may be exposed to wildfire smoke, with the following exemptions.

The Wildfire Smoke emergency rule does not apply when University personnel are:

  • Inside enclosed buildings or structures in which windows, doors, bays, and other exterior openings are kept closed, except when necessary to open doors to enter and exit
  • Inside enclosed vehicles in which the air is filtered by a properly maintained cabin air filter and that windows, doors, and other openings are kept closed except when it is necessary to open doors to enter or exit (buses, light rail, and other enclosed vehicles used for transit systems where doors are frequently opened to board and deboard passengers are not included under the exemption in WAC 296-62-08510 (2)(b))
  • Exposed to outdoor air with a Air Quality Index (AQI) that is 69 or higher for a total of one hour or less during a 24-hour period
  • Engaged in wildland firefighting

Responsibilities for the protection of outdoor workers

Air quality monitoring

University units may obtain air quality data through any of the following resources:

You may also use the information in Appendix A of WAC 296-62-08585 to collect particulate data. This involves used a direct-reading instrument to collect measurements of PM2.5. EH&S is available for this service if needed.

General precautions

When the AQI is greater than 101, it is recommended that everyone stay indoors and keep windows closed, especially sensitive groups, such as older adults and young children, pregnant women, and those with a breathing or heart condition. Read more information on the health effects of wildfire smoke and tips for protecting yourself on the Centers for Disease Control and Prevention (CDC) Wildfire Smoke webpage and in the frequently asked questions section below.

Check the Environmental Protection Agency AirNow website for a reliable report of the current and forecasted air quality in your area. AirNow provides the daily AQI, a rating of how clean or polluted the outdoor air is, along with any potential health effects and recommended steps to reduce exposure. 

The best way to protect yourself against the potentially harmful effects of wildfire smoke is to reduce wildfire smoke exposure, for example, by seeking clean air shelters and cleaner air spaces. It is recommended to keep windows and doors closed as much as possible to avoid worsening the indoor air quality.

University buildings that use heating, ventilation, and air conditioning (HVAC) systems to filter indoor air typically remove up to 90% of harmful pollutants in wildfire smoke.

In naturally ventilated buildings (buildings without mechanical HVAC systems), the indoor temperatures may rise due to windows being closed. If the room becomes unbearably hot, portable electric fans and air-conditioning units can be used to cool the space. Check with your unit leadership and the building coordinator to ensure that the facility electrical system can meet the energy demand.


Personnel must be trained on information regarding wildfire smoke before work that exposes the individual to AQI of 69 (PM2.5 levels of 20.5 µg/m3) or higher, and at least annually thereafter.

The Wildfire Smoke Safety Training course is available on the EH&S Training webpage.

Services available

During wildfire smoke events that impact UW campuses and facilities, EH&S is available for consultation and may perform a site visit depending on the situation. We are equipped to conduct site measurements for airborne particulate matter concentrations and to provide recommendations.

Visit the Indoor Air Quality page on the EH&S website for more information and instructions for requesting an indoor air quality evaluation.

To request assistance from EH&S please contact us at ehsdept@uw.edu or (206) 543-7388.

Frequently Asked Questions

Wildfire smoke is a mix of gases and fine particles from burning vegetation, building materials, and other materials. Wildfire smoke can make anyone sick. Even someone who is healthy can get sick if there is enough smoke in the air. Breathing in smoke can have immediate health effects, including:

  • Coughing
  • Trouble breathing normally
  • Stinging eyes
  • A scratchy throat
  • Runny nose
  • Irritated sinuses
  • Wheezing and shortness of breath
  • Chest pain
  • Headaches
  • An asthma attack
  • Tiredness
  • Fast heartbeat

Older adults, pregnant women, children, and people with preexisting respiratory and heart conditions may be more likely to get sick if they breathe in wildfire smoke.


Elderly persons, pregnant individuals, children, and individuals with heart or lung conditions are particularly susceptible to elevated air pollution levels and should take extra precautions to avoid exposure.

Elevated particulate matter in the air can trigger wheezing in those who suffer from asthma, emphysema, Chronic Obstructive Pulmonary Disease (COPD), or other respiratory conditions.  People with respiratory conditions should talk to their physicians to develop a personal plan for dealing with smoke, including keeping extra medications/inhalers on hand, having an active asthma action plan, and considering whether to include a N95 respirator mask in your personal emergency preparedness kit.

  • Stay hydrated by drinking water during heavy smoke events.
  • Stay inside, preferably in a room with HEPA filtered air with the doors and windows closed.  Seek shelter elsewhere if you do not have an air conditioner and it is too warm to stay inside with the windows closed.
  • Do not add to indoor air pollution. Do not burn candles or use gas, propane, or aerosol sprays. Do not fry or broil meat, smoke tobacco products, or vacuum. All of these can increase air pollution indoors.
  • Take it easier during smoky times to reduce how much smoke you inhale and avoid outdoor strenuous activities.
  • Know your air quality. Stay tuned to local media for changes in smoke or weather conditions. EPA Air Now (link is external) website is the preferred way to check your local air quality.
  • Long-term smoke events usually have periods when the air is better. When air quality improves, even temporarily, air out your home to reduce indoor air pollution, and step outside yourself when you have a chance!

Please reconsider being outside. The only way to completely avoid potential health risks from both chemicals and particulates found in smoke is to avoid exposure. If you must be active outside in smoky areas, take steps to limit your time and level of activity outdoors. Consider the use of a particulate respirator such as an N-95 to filter out some of the particulate matter. These masks do not filter harmful chemicals found in smoke and are proven to provide protection only if individually fitted by a trained technician, but provide limited particulate filtration and comfort for those sensitive to the smoke.  

Please be aware that wearing respirators can not only feel claustrophobic but can provide a false sense of security. They also increase the work of breathing which can be dangerous for those with underlying heart or lung disease.

Note that simple paper “comfort” or “dust” masks commonly found at hardware stores are designed to trap large particles, such as sawdust. These masks will not protect your lungs from the small particles found in a wildfire.

UW strongly recommends that students, faculty, or staff in these high-risk categories, and any who know they are sensitive to smoke, discuss the risks/benefits of N95 respirators with their physician beforehand, and consider purchasing one for personal use before a wildfire smoke event occurs, as part of their emergency kit.

Air quality information is measured primarily in two ways:

  1. NowCast Air Quality Index (AQI)
  2. Concentration of particulate matter 2.5 micrometers (PM2.5) in size or smaller

The table below shows the relationship between AQI and PM2.5 measurements of air quality.

PM2.5 in micrograms per cubic meter (µg/m3) Air Quality Index for PM2.5 (AQI)
20.5 69
35.5 101
555 Beyond limit of AQI

EH&S uses AQI values alone to communicate about air quality.


The National Institute for Occupational Safety and Health of the U.S. Centers for Disease Control and Prevention. NIOSH tests and approves respirators for use in the workplace. 

The method used by the U.S. Environmental Protection Agency (EPA) to communicate air quality using color-coded categories. It shows the air quality for the most current hour available by using a calculation that involves multiple hours of past data using the NowCast. The NowCast uses longer averages during periods of stable air quality and shorter averages when air quality is changing rapidly, such as during a wildfire. The NowCast is generally updated every hour. 


The concentration of PM2.5 for the most current hour available by using a calculation that involves multiple hours of [ 1 ] OTS-3201.2 past data using the NowCast. The NowCast uses longer averages during periods of stable air quality and shorter averages when air quality is changing rapidly, such as during a wildfire. The NowCast is generally updated every hour.

Solid particles and liquid droplets suspended in air, known as particulate matter, with an aerodynamic diameter of 2.5 micrometers or smaller. Measured in micrograms per cubic meter (µg/m3).

People with preexisting health conditions and those who are sensitive to air pollution who are among those most likely to experience health problems from exposure to wildfire smoke.

Examples of sensitive groups include:

• People with lung diseases such as asthma or chronic obstructive pulmonary disease (COPD), including bronchitis and emphysema, and those who smoke;

• People with respiratory infections, such as pneumonia, acute bronchitis, bronchiolitis, colds, flu, or those with, or recovering from COVID-19;

• People with existing heart or circulatory problems, such as irregular heart beat, congestive heart failure, coronary artery disease, angina, and those who have had a heart attack or stroke;

• Children under eighteen years old, and adults over age sixty-five;

• Pregnant women;

• People with diabetes;

• People with other medical or health conditions which can be exacerbated by exposure to wildfire smoke as determined by a physician.

Emissions from fires in wildlands or in adjacent developed areas.

Sparsely populated geographical areas covered primarily by grass, brush, trees, crops, or combination thereof.