Wildfire Smoke: When to Restrict Activities and How to Protect People

Who is most at risk and what smoke exposure does

Wildfire smoke is a mixture of gases, vapors, and tiny particles, some visible only under a microscope. It irritates the eyes, nose, throat, and lungs and can cause coughing, wheezing, and difficulty breathing. According to the U.S. Centers for Disease Control and Prevention (CDC) and Environmental Protection Agency (EPA), fine particles (PM2.5) reach deep into the airways, so children, older adults, pregnant people, and people with asthma, COPD, heart disease, diabetes, or chronic kidney disease face higher risk of adverse effects.

Higher risk does not make healthy adults immune: sustained exposure at unhealthy levels can produce symptoms in anyone. The working principle is simple — if it looks or smells smoky outside, reduce time outdoors and avoid strenuous exertion such as running, mowing the lawn, or heavy physical work, because harder breathing draws more smoke into the lungs.

• Children and youth under 18;
• pregnant people;
• people with asthma, COPD, and other lung disease;
• people with heart disease or diabetes;
• older adults and those who work outdoors.

Using the Air Quality Index as your decision tool

The Air Quality Index (AQI) is built to help people reduce the inhaled dose of smoke by acting on three levers: the concentration of the pollutant (be active when air is better), minute ventilation (walk instead of jog), and duration of exposure (spend less time exerting outdoors). The two most useful sources during an event are the daily AQI forecast and the Fire and Smoke Map, both on AirNow and its app; near large fires, look for Smoke Outlooks that predict air quality in six-hour blocks so you can schedule errands for cleaner windows.

The color scale tells you when to act. Green (0–50) and yellow (51–100) are generally acceptable. Orange (101–150) is "unhealthy for sensitive groups": they should reduce prolonged and strenuous outdoor activity. Red (151–200) is unhealthy for everyone: avoid strenuous outdoor exertion. Purple (201–300) and maroon (301+) are very unhealthy and hazardous: everyone should stay indoors and keep activity levels low.

• 0–50 (green): normal activity for all;
• 51–100 (yellow): sensitive groups monitor symptoms;
• 101–150 (orange): sensitive groups limit prolonged exertion;
• 151–200 (red): everyone avoids strenuous outdoor activity;
• 201+ (purple/maroon): stay indoors, minimize activity for everyone.

The clean-air room: your strongest indoor defense

The most effective protection is limiting time outdoors and making the air indoors cleaner. CDC recommends picking a room you can close off from outside air, keeping windows and doors shut, and running a portable air cleaner or filter to keep that room clean even when the rest of the building is smoky. For a central heating and cooling system, use high-efficiency filters (ideally MERV 13 or higher if the system can handle it) and switch the system to recirculate or close the outdoor-intake damper.

Equally important is not polluting the air you are trying to protect. Avoid candles, gas, propane, wood stoves, fireplaces, and aerosol sprays; skip frying or broiling food, tobacco smoking, and vacuuming. If you build a do-it-yourself box-fan filtration unit, never leave it unattended. In hot weather, closed windows raise heat risk, so monitor the CDC HeatRisk level and know where cooling centers are.

When and which respirator actually helps

Cloth masks, surgical masks, bandanas, and wet cloths are not designed to seal to the face and will not stop fine smoke particles. If you must be outdoors for extended periods or are in an ash-covered area, use a particulate respirator approved by NIOSH with the words "NIOSH" and "N95" or "P100" printed on it. Choose one with two head straps, sized to cover your nose and under your chin, and check the seal each time; leakage around the edges lets unfiltered air in.

A respirator only works worn correctly: one strap below the ears and one above, nose clip pressed firmly with both hands, and clean-shaven skin where it seals. Discard it when it gets hard to breathe through or becomes dirty. People with heart or lung conditions and pregnant people should ask a doctor before relying on one; in heat or during exertion, respirators raise heat-illness risk, so take breaks and drink water.

Children aged two and older can wear respirators, but NIOSH-approved sizes for very young children do not exist; pick a fit that covers nose and chin without blocking vision and that the child will keep on. Masks and respirators are not recommended for children under two.

Workers, schools, and organized activities

Where outdoor work cannot be avoided, employers should frequently monitor local air quality and apply the hierarchy of controls: relocate or reschedule tasks to smoke-free or less smoky areas and times, reduce the intensity of physical exertion, and give frequent breaks in clean air. If respirators are required, they must be NIOSH Approved and used within an OSHA-compliant respiratory protection program; in some jurisdictions such as California, specific rules protect workers from on-the-job wildfire smoke exposure.

Schools and youth groups should apply the same logic before scheduling physical education, practice, and outdoor play: check current and forecast AQI. At orange levels, move intensive activity indoors for sensitive children; at red and above, cut or cancel outdoor exertion for everyone and shift to indoor spaces with cleaned air. Event organizers should publish clear cancellation criteria in advance so staff and families know the plan rather than improvising mid-event.

• Set a named owner to check AQI and forecast each morning and afternoon.
• Agree on thresholds for moving, reducing, or canceling outdoor activity.
• Designate backup indoor venues with air cleaning and a communication plan.
• For workers: relocate tasks, lower intensity, take breaks in clean air.
• Review plans with participants, parents, and people with chronic conditions.

Preparing for the season and knowing when to seek help

Protection starts before the smoke arrives. For people with chronic conditions, CDC recommends talking with a clinician, following an asthma action plan if one exists, and stocking a 7–10 day supply of medicines in a waterproof, childproof container in case of evacuation. Buy foods that need no frying or broiling, identify a clean-air room, and check your filters. In hot weather, keep heat on the radar, since sealed homes can overheat.

Seek care if you develop or worsen coughing, shortness of breath, chest discomfort, palpitations, or unusual fatigue; for severe trouble breathing, chest pain, or a suspected heart attack or stroke, call emergency services or go to an emergency department. Smoke can linger for days after a fire is contained, so keep checking air quality even after flames are controlled.

These recommendations reflect U.S. CDC and EPA materials and are informational, not medical advice; other countries use different air-quality standards and thresholds, so verify local guidance. Individual decisions about health should be made with a qualified clinician.

• Before season: medicines for 7–10 days, action plan, clean-air room.
• During event: watch AQI and forecast; stay indoors as much as possible.
• First response: move to cleaner air and remove respirator if dizzy.
• Emergency: call for help with severe breathing trouble or chest pain.

A decision protocol for responsible operators

Facility managers, event organizers, and school leaders benefit from a written protocol decided in advance rather than in the moment. Name the person who checks the AQI and forecast each morning, fix the thresholds at which activities move indoors, are reduced, or are canceled, and designate indoor fallback spaces with air cleaning plus a reliable way to reach participants and families. Confirm that people with chronic conditions can access their action plans and medicines.

Flexibility matters more than a rigid number: the right call depends on the activity's intensity and duration, the participants' risk profile, and the availability of clean indoor space. If people develop cough, wheeze, or shortness of breath while carrying out routine tasks, lower the intensity or postpone the work — symptoms override a formal threshold. Document each decision so the next event runs faster and more consistently.