Wildfire Smoke

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 get help" below apply to you.

Why it matters

Smoke can make air unhealthy far from a fire, and it hits people with heart or lung disease, children, older adults and pregnant people hardest.

The numbers, in one place

Published figures for Wildfire Smoke

Measure	Figure
Air Quality Index	check daily at AirNow.gov; higher numbers mean more pollution
AQI 101-150	unhealthy for sensitive groups
AQI 151-200	unhealthy; anyone may start to feel health effects
Masks	a well-fitted N95 respirator can reduce exposure; cloth and surgical masks offer little protection from smoke
Indoors	a portable air cleaner with a HEPA filter can lower indoor smoke levels

What helps

• 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

• 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.

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
• 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 get help

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.