Wildfire Smoke: What Published Guidance Supports

Key takeaways

• Air Quality Index: check daily at AirNow.gov; higher numbers mean more pollution
• AQI 101-150: unhealthy for sensitive groups
• Most useful single change: Check AirNow.gov or the AirNow app when smoke is in your area.
• Commonest mistake: Exercising outdoors when air quality is unhealthy.
• See a doctor if any of the signs under "When to speak to a doctor" below apply to you.

What it is

Smoke from wildfires, which contains fine particles (PM2.5) that can travel hundreds of miles and harm the lungs and heart. It sits within Weather Safety. Below are the published figures, in one place.

The numbers, in one place

What helps

The advice below comes straight from the guidance cited at the foot of this page.

• Check AirNow.gov or the AirNow app when smoke is in your area
• Stay indoors with windows and doors closed, and set air conditioning to recirculate
• Create a clean room with a portable air cleaner or a do-it-yourself box fan filter
• Have a plan and extra medicines ready if you have asthma, COPD or heart disease

What to avoid

The common mistakes, including the ones that sound sensible.

• Exercising outdoors when air quality is unhealthy
• Frying food, burning candles, smoking or vacuuming indoors on smoky days
• Relying on a dust mask or bandana for protection

In depth

Wildfire smoke is a mix of gases and tiny particles from burning trees, plants, buildings and everything inside them. The particles that matter most for health are fine particles called PM2.5, which are small enough to be breathed deep into the lungs and some of which can pass into the bloodstream. They irritate the airways and trigger inflammation throughout the body, which is why smoke affects the heart and blood vessels as well as the lungs.

Because smoke can travel hundreds or even thousands of miles, people far from any fire can be exposed. Smoke levels can change quickly with the wind, and a sky that looks only a little hazy may still contain unhealthy amounts of PM2.5. That is why the Air Quality Index is more reliable than looking outside. Smoke events are becoming more frequent and longer in many parts of the US, so planning ahead is increasingly useful.

The effects range from stinging eyes and a scratchy throat to asthma attacks, worsening COPD, heart rhythm problems, heart attacks and strokes in people at risk. Healthy adults often recover quickly once the smoke clears, but repeated or long exposures are a growing concern. The goal is to reduce how much smoke you breathe, mainly by staying indoors with cleaner air, using air filtration and wearing a well-fitted respirator if you must be outside.

Signs and symptoms

• Stinging or watery eyes and a runny or stuffy nose
• Scratchy throat and coughing
• Wheezing, chest tightness or shortness of breath
• Headache and unusual tiredness
• A fast or irregular heartbeat
• Needing your rescue inhaler more often than usual

Causes and risk factors

• Living downwind of active wildfires, even at great distances
• Spending long periods outdoors, especially doing hard physical work or exercise
• Leaky homes, open windows and HVAC systems that bring in outside air
• Existing asthma, COPD, heart disease or diabetes
• Age, with children and older adults more affected
• Pregnancy
• Lack of access to air conditioning or air filtration

How it is checked

Most smoke-related symptoms are recognized from timing: they start or worsen when smoke is present and improve as air quality gets better. Your doctor will ask about your symptoms, how much smoke you were exposed to and any existing heart or lung conditions. For people with asthma or COPD, they may check breathing with a peak flow meter or spirometry and review your action plan.

If you have chest pain, a fast or irregular heartbeat or severe breathlessness, doctors may order an electrocardiogram, blood tests or a chest X-ray to look for heart or lung problems. These symptoms need urgent care, and chest pain or severe trouble breathing is a reason to call 911 rather than wait for an appointment.

Treatment and support options

Creating a clean room

Pick a room where you spend a lot of time, such as a bedroom. Close windows and doors, and run a portable air cleaner with a HEPA filter sized for the room. A do-it-yourself version using a box fan with a MERV 13 or higher furnace filter attached can also lower particle levels. Keep the room cool, since closing up a house in hot weather can create a heat risk.

Using your HVAC system

If you have central air, set it to recirculate and use the highest-rated filter your system can handle, often MERV 13. Run the fan more often to keep air moving through the filter. Change filters more frequently during smoke events, because they clog faster. Ask an HVAC technician if you are unsure what your system can take.

Wearing a respirator

An N95 or similar respirator that fits snugly around the nose and mouth can greatly reduce how many particles you breathe. It does not filter gases, and it only works if it seals well; facial hair breaks the seal. Respirators are not designed for small children. People with heart or lung disease should ask their doctor whether wearing one is safe for them.

Managing existing conditions

If you have asthma, COPD or heart disease, review your action plan with your doctor before fire season. Make sure you have enough of your medicines, know when to use your rescue inhaler and know which symptoms mean you need urgent care. Your doctor may suggest adjusting treatment during prolonged smoke events.

Prevention

• Sign up for local air quality alerts and check AirNow.gov when fires are burning
• Buy air filters and N95 respirators before fire season, when they are easier to find
• Plan where you would go if your home gets too smoky or too hot
• Keep car windows closed and set ventilation to recirculate when driving through smoke
• Avoid adding to indoor pollution with candles, frying, smoking or gas stoves on smoky days

Day to day

During a long smoke event, try to keep a routine indoors. Move exercise inside and keep it lighter, since harder breathing draws in more particles. Keep children's outdoor play short when the AQI is high, and check with schools and camps about their smoke policies. Keep pets indoors as well. Drinking enough water and using saline nasal rinses or eye drops may ease irritation.

After the smoke clears, cleaning up ash needs care. Wet down ash lightly before sweeping, wear an N95 and gloves, and avoid using leaf blowers or dry sweeping, which stir particles back into the air. Ash from burned buildings can contain harmful substances, so keep children and pets away. Smoke events can also be stressful, especially if you have had to evacuate; reaching out for support is reasonable.

For specific groups

Children

Children breathe more air for their body size and spend more time active outdoors, so they take in more smoke. Their lungs are still developing. Keep them indoors in cleaner air on smoky days, and know that N95 respirators are not designed to fit young children.

People with heart or lung disease

Smoke can trigger asthma attacks, COPD flare-ups, heart rhythm problems and heart attacks. Have an action plan and medicines ready, limit exposure aggressively and seek care early if symptoms worsen.

Pregnancy

Wildfire smoke exposure in pregnancy is linked to lower birth weight and preterm birth. Pregnant people should reduce exposure as much as possible and talk to their obstetric provider about whether wearing a respirator is right for them.

Outdoor workers

Workers who cannot avoid being outdoors breathe more smoke because of physical effort. Some states have specific rules requiring employers to provide respirators and other protections when air quality is poor. Ask your employer about the plan.

Questions to ask your doctor

• Should I change my asthma or COPD medicines during smoke season?
• Is it safe for me to wear an N95 respirator with my health conditions?
• What AQI level should prompt me to stay indoors or leave the area?
• Which symptoms mean I should go to urgent care or the emergency room?
• How can I protect my child, who has asthma, during smoke events?
• Could smoke be affecting my heart, and what should I watch for?

More questions, answered

Can I tell how bad the air is by looking outside?

Not reliably. Air can look only slightly hazy while particle levels are unhealthy, and smoke can sit higher in the atmosphere where it looks dramatic but affects ground-level air less. Check the AQI from official monitors instead.

Do air purifiers really help with smoke?

Yes. Portable air cleaners with HEPA filters, when sized correctly for the room, can significantly lower indoor particle levels. Avoid air cleaners that produce ozone, which is itself a lung irritant. A box fan with a MERV 13 filter is a lower-cost option.

Is it safe to exercise outdoors during wildfire smoke?

When air quality is unhealthy, it is best to move exercise indoors or postpone it. Hard exercise makes you breathe faster and deeper, drawing more particles into the lungs. Healthy adults can follow the AQI guidance; people with heart or lung disease should be more cautious.

Will a surgical mask protect me from smoke?

Surgical masks, cloth masks and bandanas let most fine smoke particles through because they do not seal around the face. A well-fitted N95 or similar respirator offers much better protection. None of these remove the gases in smoke.

Should I leave the area during a wildfire smoke event?

Many people can manage smoke at home with a clean room and closed windows. If you have serious heart or lung disease, cannot keep your home air clean or cool, or symptoms are getting worse, staying with family or friends somewhere with cleaner air may be sensible. Follow any evacuation orders.

Can wildfire smoke affect people far from the fire?

Yes. Smoke can travel across states and even across the country. People hundreds of miles away have experienced unhealthy air from distant fires. That is why checking local air quality matters even if there is no fire nearby.

Related topics

• What the Guidance Really Says About Air Pollution and the AQI (Environmental Health)
• Air Quality: What the Evidence Actually Says (Respiratory Health)
• COVID-19: What the Evidence Actually Says (Infectious Diseases)
• Smoke Alarms and Fire Safety: What the Evidence Actually Says (Injury Prevention)

Where to go next

• Starting Out With Wildfire Smoke
• Answers to the Common Questions on Wildfire Smoke
• Wildfire Smoke — the reference entry
• Weather Safety: The Complete Guide
• Hurricane Preparedness and Emergency Kits: Sorting the Evidence From the Noise
• Carbon Monoxide During Power Outages: What the Evidence Actually Says

When to speak to a doctor

Call your doctor if smoke makes asthma, COPD or heart symptoms worse. Call 911 for chest pain, severe shortness of breath or trouble breathing.

Where this comes from

• AirNow — Wildfire Smoke Guide for Public Health Officials
• EPA — Wildfire Smoke and Your Patients' Health
• CDC — Wildfire Smoke

How this page was put together

Every figure, recommendation and warning above is taken from the guidance named in Where this comes from. Nothing on this page is inferred, summarized or generalized beyond what those bodies publish: where they give a number, it is their number, and where they are silent, so are we. Pages are rebuilt whenever the underlying record changes. Sign-off by a named clinician, where it has happened, is shown at the top of the page along with the date.

Medical disclaimer

This article is general information, not medical advice. It cannot account for your own history, medication or circumstances. Always speak to your doctor, pharmacist or another qualified health professional before making changes that affect your treatment, and never delay seeking medical advice because of something you have read here. In an emergency, call 911.