What the AQI colors mean when wildfire smoke is in the air

One scale, six levels

The AQI turns pollution measurements into health guidance

The U.S. Air Quality Index is EPA's tool for communicating outdoor air quality and health concern. A higher AQI means more pollution and a greater potential health risk. The reported AQI reflects the pollutant with the highest index value at that place and time, so always check the listed primary pollutant too.

• EPA calculates AQI values for ground-level ozone, particle pollution, carbon monoxide, sulfur dioxide, and nitrogen dioxide.
• Fine particle pollution, called PM2.5, is the key pollutant to watch when wildfire smoke is affecting the air.
• AQI values at or below 100 are generally considered satisfactory, although people who are unusually sensitive may notice effects in the Moderate range.
• Above 100, the guidance becomes more protective—first for sensitive groups and then for everyone as the number rises.

Read the color and the number

What each EPA AQI category means

The color is a quick signal, but the category name and number provide the decision-making detail. These ranges apply to ozone and particle pollution, including wildfire smoke.

Green · Good · 0–50

Air quality is satisfactory, and air pollution poses little or no risk.

Yellow · Moderate · 51–100

Air quality is acceptable, but a small number of unusually sensitive people may need to reduce exposure.

Orange · Unhealthy for Sensitive Groups · 101–150

Sensitive groups may experience health effects. For particle pollution, this includes people with heart or lung disease, older adults, and children.

Red · Unhealthy · 151–200

Some people in the general public may experience effects, and sensitive groups may experience more serious effects.

Purple · Very Unhealthy · 201–300

EPA describes this as a health alert: the risk of effects is increased for everyone.

Maroon · Hazardous · 301 and higher

EPA describes emergency health conditions in which everyone is more likely to be affected.

A color change is not a cliff where risk suddenly begins or ends. Use the newest local value, identify the pollutant, and follow the activity guidance for your health situation.

Current is not the same as forecast

Use the NowCast for now and the forecast for planning

AirNow's current AQI is a NowCast—not a single instant reading and not tomorrow's prediction. EPA's calculation uses multiple hours of monitor data, weighting recent hours more heavily when conditions are changing quickly. That lets the familiar AQI scale describe the most current hour available.

1. Check the NowCast before a walk, run, outdoor job, practice, or other activity happening soon.
2. Use the AQI forecast to plan later today or tomorrow. State, local, and tribal air-quality forecasters issue these daily predictions where available.
3. Recheck current conditions before going outside. Smoke levels can improve or deteriorate after a forecast is issued.
4. Look at the primary pollutant. The health guidance for ozone can differ from the guidance for PM2.5 smoke.

When smoke is the concern

Use the Fire and Smoke Map—not only the AirNow dial

EPA recommends the AirNow Fire and Smoke Map during wildfire smoke events. The main AirNow dial may show ozone when ozone has the highest AQI, or it may lack a nearby PM2.5 monitor. The smoke map focuses on fine particles and provides more location detail.

• The map combines permanent and temporary PM2.5 monitors with thousands of air-quality sensors.
• It can show whether air quality is getting better or worse, along with smoke plumes, fire locations, and smoke forecast outlooks where available.
• Map colors cover approximate areas. A nearby reading may not perfectly describe conditions on your street, especially near a changing smoke boundary.
• If the air looks or smells smoky, reduce exposure even when a monitor is distant or data is temporarily unavailable.

Use the exact product name

Outlooks, forecasts, alerts, watches, and warnings are different

Several official products may appear at the same time. Their names describe different information, agencies, time periods, and hazards. Read the location, valid time, pollutant, and action statement instead of treating every colored map as a warning.

Smoke outlook

An outlook is planning information for areas where wildland fire smoke may be a concern. It describes expected smoke and air-quality patterns; it is not a monitor reading or a local evacuation order.

AQI forecast

A forecast predicts the day's AQI. It is usually prepared by a state, local, or tribal air-quality agency and can change as emissions, wind, mixing, and smoke transport change.

Air Quality Alert or Action Day

Environmental agencies may issue an alert or call an Action Day when unhealthy air is forecast. In some areas, the NWS distributes an Air Quality Alert on the agency's behalf. Follow the exact alert text for the affected counties, pollutant, timing, and recommended actions.

Watch

A watch means the named hazard is possible. A Fire Weather Watch concerns conditions that could support rapid fire spread; it does not measure the smoke concentration people are breathing.

Warning

A warning means the named hazard is expected, imminent, or occurring. A Red Flag Warning addresses critical fire-weather conditions, while an evacuation warning or order comes from local authorities. Neither replaces the current AQI.

The words “health alert” and “health warning” in EPA's AQI category descriptions communicate health concern; they do not automatically mean that the National Weather Service issued a weather watch or warning.

Reduce smoke exposure

Build a simple plan before the air turns unhealthy

Everyone should reduce wildfire-smoke exposure, but people with heart or lung disease, older adults, children and teenagers, pregnant people, and outdoor workers may face greater risk. Plan around both air quality and heat so that cleaner indoor air does not become dangerously hot.

1. Choose one room that can serve as a cleaner-air space. Keep windows and doors closed when smoke is present, and use a properly sized air cleaner if one is available.
2. If the system can safely use it, EPA recommends a high-efficiency HVAC filter rated MERV 13 or higher. Set compatible systems to recirculate indoor air instead of drawing smoky air inside.
3. Avoid adding particles indoors through smoking, candles, wood-burning appliances, frying food, sweeping, or vacuuming.
4. Reschedule strenuous outdoor activity or reduce its duration and intensity. Take breaks in a cleaner indoor space if essential work cannot be moved.
5. Cloth face coverings do not filter wildfire smoke. A well-fitting N95 respirator can reduce particle exposure when someone must be outside, but it does not remove gases and must be worn correctly.
6. Keep the cleaner-air room cool. If the home becomes too hot, move to an air-conditioned public building or cleaner-air shelter and follow local emergency instructions.