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Wildfire Smoke FAQs

For information regarding Air Quality in your area, visit the Air Quality website.

For additional information about Wildfire safety, visit the CDPH Wildfires page.

For information on N95 Particulate Mask Use and Distribution Locations, visit the Masks page.


What's in smoke that's so harmful?

Smoke is a complex mixture of water vapor, fine particles and many different chemicals, including aldehydes, acid gases, sulfur dioxide, nitrogen oxides, polycyclic aromatic hydrocarbons (PAHs), benzene, toluene, styrene, metals and dioxins. The type and amount of fine particles and chemicals in smoke varies depending on what is burning, how much oxygen is available, and the burn temperature. The fine particles from wildfire smoke create the biggest health concern.

What are some of the health effects of wildfire smoke?

Wildfire smoke contains fine particles which are respiratory irritants, and when inhaled deeply, can affect the lungs and the heart. Exposure to high concentrations of fine particles can cause persistent cough, runny nose, phlegm, wheezing, and difficulty breathing. Individuals with respiratory conditions, compromised immune systems or other significant health issues can be particularly susceptible to fine particles. However, exposure to wildfire smoke can affect healthy people, too, causing respiratory symptoms and reductions in lung function. The body's ability to remove foreign materials from the lungs, such as pollen and bacteria, can be affected, too.

Even short-term exposure (i.e., days to weeks) to fine particles can aggravate pre-existing heart and lung disease. 

Are some people more affected than others?

Not everyone who is exposed to wildfire smoke will have health problems: age, individual susceptibility – including the presence or absence of pre-existing lung disease such as asthma, Chronic obstructive pulmonary disease (COPD) or heart disease, and other factors – determine whether someone will experience smoke-related health problems.

Specific groups, including children, pregnant women, elderly individuals, and people who are sensitive to air pollution (such as those with pre-existing heart and lung disease) should take precautions to limit exposure to wildfire smoke.

Anyone concerned about the potential health implications of exposure to wildfire smoke should discuss this with their primary healthcare provider and check the Air Quality Index on the AirNow website each day for the air quality forecast and for information about ways to reduce exposure.

What if I have asthma, another lung disease or heart disease? 

If you have asthma or another lung disease, make sure you follow your healthcare provider's directions about taking your medicines and following your asthma action plan. Have at least a five-day supply of medication on hand and call your healthcare provider if your symptoms worsen. For individual concerns from specific smoke events, consult a medical professional.

If you have cardiovascular disease, follow your healthcare provider's directions and call if your symptoms worsen. If you think you are having a heart attack or stroke, dial 9-1-1.

How can I reduce exposure to wildfire smoke?

Individuals who are particularly sensitive to smoke should consider temporarily evacuating an area with unhealthy levels of wildfire smoke, even if a mandatory evacuation order isn't in place, until air quality conditions improve. 

For most people, staying inside in a safe place with the doors and windows closed can usually reduce exposure to air pollution by at least a third or more. 

If you have a central air conditioning system in your home, set it to re-circulate or close outdoor air intakes to avoid drawing in smoky outdoor air. Be sure to change your air filter on a regular basis.

Some communities have designated clean air shelters where people can go for respite from smoky conditions. This is particularly important for people without air conditioning on hot smoky days, when staying indoors with windows closed can be hazardous. Places to consider going include public libraries, hospitals, movie theaters, and other public buildings with good HVAC systems.

Reduce other sources of indoor air pollution: smoking cigarettes, using gas, propane and wood-burning stoves and furnaces, spraying aerosol products, frying or broiling meat, burning candles and incense, and vacuuming can all increase particle levels in a home and should be avoided when wildfire smoke is present.

What if I don't have air conditioning/HVAC?
Leaving the area may be best for those with health conditions that put them at higher risk from exposure to smoke. Go to a local public building with air conditioning such as a movie theater, mall or library. Seek a local clean air shelter. Seek shelter at a friend or relative's home away from smoke.
If you must stay put:
Stay as cool as possible and drink plenty of water.
Set up an air purifier in a basement room, if possible. For a list of recommended air purifiers visit the California Air Resources Board

Should I wear a mask during a wildfire, even if it's not really smoky where I am?
Surgical masks, dust masks, bandanas or other face coverings do not offer protection from particle pollution. Inexpensive paper "comfort" or "dust" masks commonly found at hardware stores are designed to trap large particles and do not provide enough protection for your lungs. 
Mask use may give the wearer a false sense of security, which might encourage too much physical activity and time spent outdoors. Also, wearing a mask may actually be harmful to some people with heart or lung disease because it can make the lungs work harder to breathe.


Respiratory masks may be beneficial for some people, provided they are worn properly.

People with respiratory or heart conditions should consult with their healthcare provider prior to wearing a respirator mask. Respirator masks can be effective in reducing exposure to smoke particles. However, they should only be used after first implementing other, more effective methods of exposure reduction, including staying indoors with doors and windows closed, reducing activity, and using HEPA air cleaners indoors to reduce overall smoke exposure. 

For adults, NIOSH N95 or P100 masks, when worn correctly, have been shown to filter particles and improve the quality of the air being inhaled.  Masks can be ordered online or purchased at hardware stores. 

Children should not wear these masks – they do not fit properly and can impede breathing. If the air quality is poor enough that a child requires a mask, the child should remain indoors, in a safe place, and evacuation should be considered.
For information on using masks for wildfire smoke, review these tips from the U.S. Environmental Protection Agency


How can I tell if the air is unhealthy?

Many local news and local air quality agencies report air quality forecasts on their websites, especially when there is a wildfire. You can also check the Air Quality Index (AQI) for current air quality in your area. 
You can also see the location of fires, the path of smoke plumes, and air quality information on the AirNow website under "Current Fire Conditions".
The AirNow program accepts, stores, and displays data provided by air quality agencies on an hourly basis. The data is available to the public via national, regional, and local maps on airnow.gov and through email notifications, widgets, and smart-phone apps.


What is the Air Quality Index (AQI)?
The AQI is used to report information about the most common air pollutants, including particulate matter (PM2.5 or PM10) and ozone. For more information, visit AirNow.

How does wildfire smoke affect pets and livestock?

The effects of smoke are similar for humans and animals. High levels of smoke may irritate your animal's eyes and respiratory tract. Strategies to reduce animals' exposure to smoke are also similar to those for humans: reduce the time spent in smoky areas, provide animals with plenty of water, limit activities that will increase breathing and reduce exposure to dust or other air pollutants. If your pet or livestock is coughing or having difficulty breathing, contact your veterinarian.

How can wildfires affect drinking water quality?

Wildfires destroy plants that stabilize soil. By burning ground cover, fires also release chemicals such as nitrates and phosphates that affect water quality. Erosion and release of these chemicals into surface water can decrease the quality of drinking water. Nitrates and phosphates can also promote growth of harmful algae. Flame retardants used by firefighters may also find a way to drinking water sources. Water suppliers will monitor your drinking water source so check with them to see if the water is safe to drink and use.

When should local officials issue warnings or cancel local activities?

School and local officials should consider the following when deciding to close or curtail local activities or events due to wildfire smoke:

  • Is the activity being held inside or outside?
  • Do smoke levels reduce visibility and make it unsafe to travel to the activity?
  • Are highly sensitive groups such as asthmatic children participating?
  • What time of day will activities be held?
  • Are smoke forecasts available for the day? Based on the smoke forecast, will the smoke level be higher or lower at the time of the activity and at the time individuals will travel to the activity?
  • Are smoke levels inside public buildings likely to be similar to or lower than those in private homes? For example, if local populations do not have air conditioning and the activity is held inside a public building that does have air conditioning and it is hot and smoky outside, it may benefit the public to seek relief indoors.
  • Is it practical to cancel part of the activity?
  • Are smoke forecasts likely to put any or all populations at increased risk? See below for Recommended Actions.

Is it practical to continue with the event as planned but issue a warning for sensitive groups? For example: holding the high school football game but issuing a warning that encourages sensitive groups — such as grandparents and young children — to stay at home and not attend the event?

For more information, click here Wildfire Smoke: A Guide for Public Health Officials

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