Get the Facts

What is the Spare the Air program and who’s involved?

 In 1991, the Spare the Air program was established by the Bay Area Air Quality Management District to reduce air pollution and provide advance notice when air quality is forecast to be unhealthy.

Because most air pollution is preventable, Spare the Air is focused on educating the public and promoting changes in behavior that will help prevent unhealthy air quality. The program reaches out to several audiences:

  • AirAlerts are an email service that informs the public the day before a Spare the Air Alert is called. It encourages Bay Area residents to modify their behavior to prevent unhealthy air quality and gives advance notice to people with respiratory sensitivities, such as asthma or emphysema. Sign up to receive your own AirAlerts.
  • The Employer Program provides more than 2,100 businesses with free tools to educate employees about pollution prevention and advises them when a Spare the Air Alert is issued. For more information or to sign up for the Employer Program, click here
  • Community Resource Teams provide an opportunity for local residents to work together and plan educational activities and programs that reduce air pollution in their communities. Join your area’s resource team.
What is a Spare the Air Alert?

A Spare the Air Alert is called when air quality is forecast to be unhealthy. A Spare the Air Alert is issued the day before unhealthy air is forecast. In the summer, Bay Area residents are asked to reduce their driving to help minimize pollution, and people who are sensitive to unhealthy air are advised to limit their time outdoors, particularly in the afternoon hours.

Because ozone is a preventable pollutant, doing things like cutting back on driving and the use of other gasoline powered equipment can make a substantial difference in the amount of pollution that occurs.

When a Spare the Air Alert is called in the winter, between November and February, the use of wood-burning devices is prohibited indoors and outdoors.

When do Spare the Air Alerts usually occur?

In the Bay Area, the summer Spare the Air season generally runs from April through October. During this period, vehicle exhaust and hot temperatures combine to form smog.

In the winter, cold temperatures and still air trap smoke close to the ground to create unhealthy air quality. When air quality is forecast to be unhealthy between November and February, a Winter Spare the Air Alert is called and the use of all wood-burning devices is prohibited both indoors and outdoors.

How will I know when a Spare the Air Alert has been called?

For those who sign up for e-mail AirAlerts, these will be issued the day before Spare the Air Alerts go into effect.

Spare the Air Alerts are also shown prominently on the and websites.

Many television and radio stations also announce Spare the Air Alerts. Several Bay Area newspapers carry the air quality forecast, usually on the weather page of the papers.

Residents can also check the daily forecasts on the home page of this Spare the Air website, or call the Air District's toll-free line at 1-800-HELP AIR.  In the winter, residents can also call 1-877-4NO-BURN.

Can I receive an AirAlert?
Yes. AirAlerts are automatically emailed to the media, participating employers, cities and counties, and any individual who requests it.  Sign up to receive your own AirAlert.  In addition to receiving email AirAlerts, there are two optional features to consider.
  • Get your AirAlert wherever you are by signing up to receive it as a text message in your cell phone, and
  • You can sign up to receive a daily Air Quality Forecast via email, as well.
What causes air pollution?

Air pollution can be both natural - such as fires or volcanic eruptions - and man-made. Most of the air pollution in the Bay Area is man-made, and results from industrial processes and everyday activities like driving, boating, using household products or lawn and garden equipment, burning wood, painting, barbecuing, etc.

In the summertime, ground-level ozone causes the most serious air quality problems. Commonly referred to as "smog", ozone is a gas formed when sunlight reacts with oxides of nitrogen and volatile organic compounds emitted by cars, buses, trucks, construction equipment, gas stations, refineries, and many other sources.

While some ozone is produced every day, cooler temperatures and steady winds normally keep it from accumulating to unhealthy concentrations. However, on long, hot, stagnant days, ozone can build up to levels that violate federal and state health-based standards.

In the wintertime, especially between the months of November and February, particulate matter, or soot, is the major air quality concern. Tiny particles, either solid or liquid, can be produced by a variety of natural and man-made sources. Particles less than 10 micrometers in diameter can cause significant health problems, with those under 2.5 micrometers, known as "fine" particles, considered to be the most dangerous. These latter are produced by any kind of combustion (motor vehicles, wood burning, power plants, etc.) and some industrial processes.

What’s the difference between “good” and “bad” ozone?

Ozone can be good or bad, depending on where it is.

Ozone is a molecule that is similar to oxygen (O2), except that it consists of three oxygen atoms (O3) and tends to be unstable. It is found in both the upper and lower atmosphere.

Stratospheric or "good" ozone occurs naturally, high in the atmosphere from about 15 to 35 miles above the earth's surface. Here, it protects us by absorbing the sun's damaging rays and is essential for human, plant, and animal life on earth.

Ground level or "bad" ozone is a pollutant that damages human health, crops, and the environment. Ground-level ozone develops from chemical reactions that occur between sunlight and the emissions from some human activities. For example, exhaust from cars, lawn mowers, leaf blowers, and other gas-powered engines, as well as emissions from power plants, dry cleaners, paints, and even some common household products all react with the sun and create bad ozone.

Can you see ozone?

No, ozone is a colorless gas. However, on days with high levels of ground-level zone, there is usually poor visibility. This is caused by two factors:

  • The reddish-brown haze is from oxides of nitrogen, better known as NOx. NOx is converted into ozone air pollution when it "cooks" in the direct ultraviolet rays of the sun.
  • Fine particles (often referred to as “particulate matter”) suspended in the air also contribute to reduced visibility. Fine particles consist mainly of soot and other by-products of combustion, particularly from automobile exhaust.
When the air looks murky, is it always from pollution?

Not always. Small particles of water vapor can cause light to be scattered so thoroughly that the blue of the sky does not come through. This phenomenon is common in the South Bay during warm weather.

What are the health effects of air pollution and who is affected?

Many residents experience some kind of air pollution-related symptoms such as watery eyes, coughing, or wheezing. Even for healthy people, polluted air can cause respiratory irritation or breathing difficulties during exercise or outdoor activities. Your actual risk depends on your current health status, the pollutant type and concentration, and the length of exposure to polluted air.

The people most susceptible to severe health problems from air pollution are:

  • Individuals with heart or lung disease
  • Individuals with respiratory problems such as asthma or emphysema
  • Pregnant women
  • Outdoor workers
  • Children under age 14 whose lungs are still developing
  • Elderly residents whose immune systems are weaker
  • Athletes who exercise vigorously outdoors

High air pollution levels can cause immediate health problems, such as:

  • Aggravated cardiovascular and respiratory illness
  • Added stress to heart and lungs causing them to work harder to supply the body with oxygen
  • Damaged cells in the respiratory system
  • Damage to deep portions of the lungs, even after symptoms such as coughing or a sore throat disappear
  • Wheezing, chest pain, dry throat, headache, or nausea
  • Increased reactivity to allergens and particles
  • Eye irritation
  • Reduced resistance to infection, increased fatigue, or weakened athletic performance

Long-term exposure to polluted air can have permanent health effects, including:

  • Accelerated aging of the lungs and loss of lung capacity
  • Decreased lung function
  • Development of diseases such as asthma, bronchitis, emphysema, and possibly cancer
Is it safe to do vigorous exercise during a Spare the Air Alert?

During a Spare the Air Alert in the summer, it is usually safest to exercise in the morning because ground-level ozone generally doesn't build up to unhealthy levels until the afternoon.

Winter pollution patterns are somewhat inconsistent, but in general fine particle pollution peaks when temperature inversions are strongest in the evening and overnight through the early morning hours. On many winter days when a Winter Spare the Air Alert is in effect, the warmer middle part of the day is often safest for exercising.

Are there any other environmental consequences of ground-level ozone?

Ground-level ozone also causes damage to plants and crops.

  • Ozone interferes with the ability of plants to produce and store food so that growth, reproduction, and overall plant health are compromised. Plants and trees weakened in this way become more susceptible to disease, pests, and environmental stresses.
  • Ozone can kill or damage leaves so that they fall off the plants too soon or become spotted or brown. These effects can significantly decrease the natural beauty of an area, such as in national parks and recreation areas.
  • Ozone has also been shown to reduce agricultural yields for many economically important crops, such as soybeans, kidney beans, wheat, and cotton.

Scientists believe the effects of ground-level ozone on long-lived species, such as trees, add up over many years, so that whole forests or ecosystems can be affected.

What are the Bay Area’s major sources of summer air pollution?

Overall, mobile sources - particularly cars and light duty trucks - are the biggest source of Bay Area air pollution, contributing 75 percent of the emission inventory.


What can I do to help reduce summer air pollution?

There's a lot you can do, probably much more than you realize. Taking any of the actions listed below will help, and the more you do, the more air pollution you will help prevent.

The biggest action you can take is to drive less. Here are a few ideas to consider:

  • Burn calories not fuel – use your legs and walk or bike
  • Take public transit and read a book during your commute
  • Call 511 to find rideshare opportunities
  • Put off all nonessential trips and activities that require engines until the air is better
  • Telecommute if your employer will allow it
  • Take your lunch to work and avoid mid-day driving

If you must drive:

  • Offer a ride to a friend or coworker
  • Combine trips – your car emits more pollution right after a cold start
  • Run your errands at night, after dark
  • If you must refuel, do it after dark and don’t top off the tank
  • Drive your most fuel-efficient car
  • Keep your car well-tuned and your tires inflated
  • Drive smoothly, this saves fuel and lowers emissions
  • Drive the speed limit, higher speeds mean more pollutants
  • Consider purchasing a reduced-emission vehicle, such as a hybrid.

Things to do at home:

  • Use an electric or old fashioned push lawn mower
  • If you can’t put off mowing with a gas mower, do it late in the day
  • Use a broom instead of a leaf blower
  • If you barbecue, use a gas grill instead of charcoal 
  • Turn off the lights and any other appliances you can do without
  • Use water-based paints
  • Go “natural” for the day and keep your hairspray in the cabinet
  • Keep all aerosol spray cans in the cabinet until the air improves
Do I have to worry about a Spare the Air Alert if the forecast for my city is “good”?

Yes, if there is a Spare the Air Alert in effect.

Air is almost always on the move, and pollution created in one area can drift to another where it can "cook" into smog later in the day. If the forecast for your area is good, you don't have to worry about your health, but what you do that day can make a big difference in the lives of others. This is particularly true in the Bay Area where winds tend to blow pollution from San Francisco and other urban areas into neighboring valleys in the East and South Bay.

How can I monitor air quality in my area?
Daily air quality forecasts are available at Daily air quality forecasts are also available on the Air District's toll-free phone line at 1-800-HELP-AIR. Many newspapers in the Bay Area also carry daily air quality forecasts.
What is an ozone movie?

Ozone Movies use real-time air monitoring data to show ozone air pollution levels throughout the region, by animating ozone concentrations as they build up on a map of the Bay Area.

What are the harmful health effects of ozone?

Ground-level ozone can cause several types of short-term health effects:

  • Ozone can irritate the respiratory system. Ozone can cause coughing, irritate your throat, eyes, or nose, and/or cause headaches. These symptoms can last for a few hours after ozone exposure and may even become painful.
  • Ozone can reduce lung function. "Lung function" refers to the amount of air that you draw in when you take a full breath and the speed at which you are able to blow it out. Ozone can make it more difficult for you to breathe as deeply and quickly as you normally would.
  • Ozone can aggravate asthma. When ozone levels are high, more asthmatics have asthma attacks that require a doctor's attention or the use of additional medication. Ozone makes people more sensitive to allergens (such as dust mites, pets, and pollen) which are the most common triggers for asthma attacks.
  • Ozone can inflame and damage the lining of the lung. Ozone's effect on the lining of the lung is comparable to the effect of sunburn on the skin. Ozone damages the cells that line the air spaces in the lung. Within a few days, the damaged cells are repaired, just as our skin recovers from a sunburn naturally.

Scientists suspect that ozone may have other effects on people's health, as well. Ozone may aggravate chronic lung diseases, such as emphysema and bronchitis. Also, studies in animals suggest that ozone may reduce the immune system's ability to fight off bacterial infections in the respiratory system.

Most of these effects are considered short-term because they eventually cease once ozone levels subside. However, there is concern that repeated short-term damage from ozone exposure may permanently injure the lung. For example, repeated ozone impacts on the developing lungs of children may lead to reduced lung function as adults.

Who is most at risk for experiencing the health effects of ozone?

  • Children. Children are more sensitive to pollution than adults. Children typically spend more time and are more active outdoors. Pound for pound, they breathe more than adults. Their air passages are narrower than adults', so it takes less inflammation or irritation to obstruct a child's airways. Children are also more likely to have asthma or other respiratory illnesses.
  • Adults who are active outdoors. Healthy adults of all ages who exercise or work vigorously outdoors are considered a "sensitive group" because they have a higher level of exposure to ozone than people who are less active outdoors. Ozone is typically a problem in the afternoon due to pollution generated in the morning.
  • People with respiratory diseases, such as asthma. There is no evidence that ozone causes asthma or other chronic respiratory disease, but these diseases do make the lungs more vulnerable to the effects of ozone.
  • People with unusual susceptibility to ozone. Scientists don't yet know why, but some healthy people are simply more sensitive to ozone than others.
Why did the Air District pass the Wood Burning Rule?
The Air District passed the Wood Burning Rule to limit harmful health impacts from fine particulate matter, or soot, a dangerous pollutant that can easily bypass filters in your nose and throat and penetrate deep into your lungs On cold, still winter days and nights, wood smoke is the single largest source of air pollution in the Bay Area. This pollution can cause serious health effects, particularly to children, older adults and those suffering from respiratory illnesses.

On cold, still winter days and nights, about one-third of the particulate pollution comes from wood smoke.

Can we burn manufactured logs during a Winter Spare the Air Alert?

No. The rule prohibits burning any solid fuel, including pellets and manufactured logs.

How do you determine violations of the Wood Burning Rule?

Air District inspectors do a visual inspection of a home or business that is suspected to be burning during a Winter Spare the Air Alert . If they are found to be in violation of the Wood Burning Rule, inspectors document the violation and send the information to headquarters for verification. After the violation is verified, first-time violators will be issued a Notice of Violation, but will have an opportunity to take the Air District’s Wood Smoke Awareness School online or by mail in lieu of paying a fine. Those who are found in violation a second time are issued a NOV citation and are subject to a $500 fine. Repeat violators who subsequently continue to burn in violation of the regulation will face increasing financial penalties.

Do inspectors knock on doors of violators?

No, air quality inspectors do not knock on doors of those found to be burning during a Winter Spare the Air Alert.

How many air quality inspectors do you have?

The Air District has 70 inspectors throughout the Bay Area.

If I have no other source of heat, can I burn? Are there exemptions available?
If a wood-burning stove or fireplace is your sole source of heat and there is no other permanently installed heating system (e.g. gas, electric or propane) in your home or business, there is an exemption available. Call 877-4-NO BURN (877-466-2876) for more information or visit the wood burning compliance page.
What triggers the Air District to call a Winter Spare the Air Alert?

From November through February, the Air District issues a Winter Spare the Air Alert when air quality is anticipated to reach unhealthy levels and exceed the federal 24-hour average standard for PM2.5, which is 35 micrograms per cubic meter and corresponds to 100 on the AQI scale.

How can the public check if there’s a Winter Spare the Air Alert in effect?
Visit or to see if an alert has been issued.
You may also call 1-877-4NO-BURN (1-877-466-2876) to check the Winter Spare the Air Alert status and to report wood smoke complaints.

Sign up to receive automatic phone alerts by calling 1-800-430-1515. Residents can also sign up for AirAlerts to receive e-mail notification when Winter Spare the Air Alerts are called.
I did not receive my phone/email alert. What should I do?
Make sure you clicked the appropriate link on your confirmation e-mail from Enviroflash when you signed up. Check your SPAM/ junk mail folder and add and to your safe sender’s list. If you still do not receive the email alerts, email us at

If you’re not receiving your phone alerts, email us at so that we can check our records.
How many Winter Spare the Air Alerts do you expect this winter?

On average, there are 15-20 Winter Spare the Air Alerts each winter.

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