Wildfire / Smoke

Air Pollution and Spare the Air Days

Air quality emergencies can be caused by particle pollution (particulate matter) such as dust, dirt, soot, smoke or drops of liquid.  Some particles are large enough or dark enough to see, for example you can see smoke in the air. Others are so small you cannot see them in the air.  Effects of particulate pollution on campus may be felt when meteorological conditions, such as an inversion layer, trap particulates in the air we breathe.  Fortunately, the San Francisco fog usually moves in with cooling ocean breezes to clear away the air pollution. There are times however where this does not occur for several days in a row.  The Bay Area Air Quality District may issue “Spare the Air” alerts for particular days in anticipation of a weather event that could cause an increase in particulate matter.

More information can be found at the Environmental Health & Safety website and at the Centers for Disease Control Air Quality and Physical Activity.

WildFire Smoke Drift

The major wildfires in California have the potential to cause air quality emergencies.  Even distant wildfires in the Sierra Mountains or further north, can result in significant smoke drift that dramatically  impacts the air we breathe on campus. When an air quality emergency occurs, AlertSU messages will advise the campus community to take common sense steps to address personal health and comfort:

  • Stay indoors as much as possible.
  • When indoors, keep windows and doors closed.
  • In vehicles, use air-recirculation mode.
  • Drink plenty of water to help minimize potential irritation.
  • When outdoors limit prolonged and heavy activity. Consider the difference between a short bike ride to class, and a long vigorous run.
    • Prolonged exertion: This means any outdoor activity that you’ll be doing intermittently for several hours and that makes you breathe slightly harder than normal. A good example of this is working in the yard for part of a day. When air quality is unhealthy, you can protect your health by reducing how much time you spend on this type of activity.
    • Heavy/Strenuous exertion: This means intense outdoor activities that cause you to breathe hard. When air quality is unhealthy, you can protect your health by reducing how much time you spend on this type of activity.
  • If you do need to be outside, monitor the air conditions and potentially shift activities to when the air quality has improved.
  • Remember you can use the Marguerite shuttles to get around campus, there are many routes available, check the Stanford Marguerite website for more information.
  • If you have outdoor activities monitor the conditions and limit your exposure.
  • Airnow.gov  is an online resource where you can monitor current air quality conditions, and learn more information.
  • Consult with your healthcare provider if you experience smoke related health issues.
  • Given that the above precautions are taken, masks are not recommended at this time for healthy individuals. Using respirator masks can make it harder to breathe, which may worsen existing medical conditions. For sensitive populations, including those with lung or heart disease or who are chronically ill, we recommend consulting with their personal health care provider before using any mask. Further considerations regarding N95 mask use can be found at the Cal OSHA website.

For individuals who may experience smoke-related health issues, we recommend consulting with one’s primary healthcare provider.



  • Minimize outdoor activities and keep the children indoors as much as possible.  Parents who have specific health concerns should consult their child’s pediatrician for further advice.


  • Individuals experiencing smoke-related distress symptoms should contact Vaden Health Center for further consultation.


  • Department will adjust work schedules and limit operations that expose staff to poor outdoor air quality.
  • For some operations where outdoor exposure is unavoidable, masks will be made available for staff who are anticipated to be exposed to poor air quality. Check with your department supervisor if you anticipate needing to work outdoors during a period of poor air quality.


PIs/Supervisors should review their group’s work activities and apply the following best practices:

  • Postponing prolonged or strenuous outdoor work.
  • Avoiding building-to-building foot travel where possible by scheduling video/phone conferencing, etc.
  • Keeping an open workplace dialogue, ensuring any related concerns and questions

When necessary, Stanford may issue the following information on the use of N95 masks in air quality emergencies:

N95 Masks – Safe Usage Considerations

EH&S continues to stress that the best way to prevent wildfire smoke inhalation is to remain indoors and limit strenuous outdoor activities as much as possible. If electing voluntary use of an N95 mask, users should heed the following considerations:

  • For sensitive individuals, including those with lung/ heart conditions, such as asthma, we recommend consulting with their personal health care provider before using any protective mask.
  • Users might be tempted to stay outdoors longer because they think they’re protected. Continue to limit outdoor activity, even while wearing an N95 mask.
  • As mask effectiveness strongly depends on face fit/seal. N95 users should be clean-shaven so no facial hair interferes with the seal.
  • N95 use FAQs provided by Cal/OSHA:

General Indoor Air Quality During an Air Quality Emergency

Provided doors and windows are kept closed, air quality in buildings will be much better than outdoor conditions. How much better will vary depending on the rate at which air “leaks” into the building but is especially dependant on the quality of the air filters used in the ventilation system. For campus buildings, ventilation systems are typically equipped with high-efficiency air filters (MERV 13 rating) that provide at least 90% filtration efficiency of fine particulate matter as small as 1.0 micron in diameter. Typical applications for MERV 13 rated filters include hospitals/ healthcare and other environments that have a higher demand for air quality. To further maximize indoor air quality, campus ventilation systems have, where possible, implemented a smoke mitigation protocol which further reduces the infiltration of air pollutants/odors by minimizing the amount of outdoor air pulled into the building. Note that laboratory buildings continue to provide filtered 100% outdoor air.

Despite highly efficient building air filtration systems in place, smoke odors may still be noticeable indoors during large-scale regional wildfires.  Although some may experience varying levels of smoke-related irritation while indoors, building air filtration systems consistently allow for better air quality than found outdoors, and remain the best means for minimizing smoke exposure during extended periods.

(NOTE:  OSHA is releasing guidelines for employees using N95 masks in air quality emergencies.  When this guidance is received, it should be included here.)

Toxic Chemical Release

On rare occasions, a toxic chemical may be released into the air from spills or fires at manufacturing or industrial facilities.  If a strong odor or irritating symptoms are expected to be experienced on campus, Stanford can issue an AlertSU message advising the campus community to shelter in place and take other precautions.