Wildfire Smoke and Air Quality: How to Read AirNow’s Smoke Map
The AirNow Fire and Smoke Map shows fine particle pollution (PM2.5) during fires, colored by the U.S. Air Quality Index. It combines permanent regulatory monitors, temporary monitors placed for smoke events, and low-cost air sensors whose readings are corrected to be more comparable with the permanent monitors. Each reading describes the air at that one location, and EPA says smoke can vary considerably even over small distances and short periods of time.
The map is a joint effort of the U.S. Environmental Protection Agency and the U.S. Forest Service-led Interagency Wildland Fire Air Quality Response Program. It is online at fire.airnow.gov.
What does the Fire and Smoke Map show?
The map layers can be switched on and off with the settings gear. EPA’s Fire and Smoke Map FAQ (June 2026) describes these layers:
- PM2.5 readings as colored circles, using the NowCast AQI for the most recent hour.
- Smoke plumes outlined from satellite data by trained analysts at NOAA’s Hazard Mapping System.
- Fire icons for large incidents from National Interagency Fire Center (NIFC) situation reports and for satellite-detected fires.
- Smoke Outlooks, daily smoke forecasts issued by Air Resource Advisors assigned to large wildfires.
- Transport winds from NOAA’s High-Resolution Rapid Refresh (HRRR) model, which give a general direction for smoke plumes.
The map shows only particle pollution. For ozone and PM10, EPA points users to the main AirNow interactive map, which uses permanent monitoring stations.
What do the circle sizes and colors mean?
Circle size tells you what kind of device is reporting. Circle color shows the NowCast AQI category. A gray circle means data is not available.
| Circle | Device | Operated by |
|---|---|---|
| Large | Permanent, regulatory-grade monitor used for official AQI reporting on AirNow.gov | Generally state, local or Tribal air quality agencies |
| Medium | Temporary monitor placed for a smoke event, such as an E-BAM or E-Sampler | Agencies monitoring the smoke event |
| Small | Air sensor that meets EPA performance targets: PurpleAir, Clarity, SensWA or SensOR (as of June 2026) | Commercial manufacturers; SensWA by Washington Ecology and SensOR by Oregon DEQ |
The AQI for PM2.5 is a 24-hour index. To show the latest hour, AirNow uses the NowCast, which uses longer averages when air quality is stable and shorter averages when it changes quickly, such as during a wildfire. Our guide to the AQI and the NowCast explains the six categories.
How are sensor readings different from official monitors?
EPA describes air sensors as non-regulatory technology that is lower in cost, portable and generally easier to operate than regulatory monitors. They appear on the map to give information in areas without official monitoring stations.
Sensor data on the map is corrected to be more comparable with the data reported by permanent monitors. Sensors must pass quality-control screening, and newly registered sensors may take up to 48 hours to appear. Sensors that agencies flag as problematic can be removed, for example sensors strongly influenced by a local pollution source or listed at the wrong location.
As of June 2026, EPA says sensor data is not used on other AirNow maps. It is not used to generate the current NowCast AQI or the forecast AQI on the main AirNow site. Sensor data is also not used to decide whether an area meets national air quality standards; only federal reference or equivalent method monitors count for that.
Why do readings vary across a city?
A monitor or sensor reports the air at its own location for a given time. EPA says how closely that matches the air where you are depends on your distance from it, wind speed and direction, terrain, the location of PM2.5 sources, and the size and amount of particles emitted.
When PM2.5 levels are stable, winds are light and no sources sit between you and the monitor, EPA says your air quality should be similar to a monitor several kilometers away. When levels are changing, smoke plumes move through, sources are nearby, or hills and valleys separate you from the monitor, the gap can be larger. Two nearby sensors can disagree for the same reasons.
Clicking a circle also shows a trend based on the most recent data from nearby PurpleAir sensors, usually from the past 30 minutes. EPA labels the trend Stable, Variable, Worsening or Improving. A Worsening or Improving trend names the category the NowCast may reach in the next few hours if conditions stay the same.
What do smoke plumes and fire icons tell you?
Plumes show where satellites saw smoke, not what people are breathing. EPA notes that satellites detect smoke anywhere in the atmosphere, including smoke high above the ground, so a plume on the map may not affect air quality at ground level. The monitor and sensor circles measure air near the ground, and EPA calls them the most reflective of the air we breathe.
Satellites can see smoke only during daylight on clear days. Plume data becomes available in the late afternoon, Eastern time, and is removed in the early morning when it is outdated.
EPA cautions that large-incident information on the map may not be updated for several days. It also says fire positions from satellite detections should be used as general guidance, not for tactical decisions such as evacuations, without other information confirming the fire. Our guide to satellite fire detections explains what a hotspot can and cannot show. Our live list of active US wildfires brings the official NIFC and NASA FIRMS data together in one place.
What do EPA and CDC advise when smoke is in the air?
Protective actions come from public health agencies, not from this site. These points are quoted or summarized from EPA’s Reduce Your Smoke Exposure page and CDC’s wildfire safety guidelines:
- EPA: “Check your state, local, or Tribal air quality agency’s website or the AirNow Fire and Smoke Map” for current conditions and forecasts.
- CDC: “Stay inside if authorities tell you to do so.”
- EPA recommends high-efficiency filters, MERV 13 or as high as your system can handle, for central air or forced-air systems, and a “cleaner air room” with a portable air cleaner.
- CDC: “If your system has a fresh air intake, set the system to recirculate mode or close the outdoor intake damper.”
- EPA: “If it is smoky outside, avoid strenuous activities, such as mowing the lawn or going for a run.”
- CDC says a respirator fits tightly to the face to filter out smoke and that “An N95 or P100 is most protective.” EPA: “Do not rely on dust masks or bandanas for protection from smoke.”
CDC lists people with chronic conditions like asthma, COPD, diabetes, chronic kidney disease or heart disease, those who are pregnant, children and responders among those most at risk from smoke.
Heat changes the advice. EPA’s Fire and Smoke Map FAQ has a table for smoke during a Heat Advisory or Extreme Heat Warning. At Unhealthy for Sensitive Groups and above, its list includes “Do not close windows if there is no air conditioning.” Heat alerts come from the National Weather Service; our guide to heat alerts explains them. CDC adds: “Always follow instructions given by local emergency management officials.”
Bottom line
The Fire and Smoke Map puts monitors, sensors, smoke plumes and fire locations in one view, but each circle describes one spot. Large circles are official monitors, small circles are corrected sensors, and plumes show smoke that may be high overhead. Fire icons can be days old. Use the map with your local air agency, health officials and the National Weather Service. Our current AQI readings by city show the official AirNow monitor data.
FAQ
Why does AirNow show green when it smells smoky?
EPA says particle levels in smoke can vary considerably over small distances and short periods, so monitors in the same area can show different NowCast categories. The main AirNow site does not include sensor data. The Fire and Smoke Map does, and sensor data updates more frequently.
Is a PurpleAir reading the same as the official AQI?
No. On the Fire and Smoke Map, PurpleAir and other sensor readings are corrected to be more comparable with regulatory monitors and are shown as small circles. EPA does not use sensor data for the main AirNow NowCast, forecasts or compliance with national standards.
What is the difference between the NowCast AQI and the hourly PM2.5 number?
The hourly PM2.5 concentration is a 1-hour average measured by a monitor or sensor, in micrograms per cubic meter. The NowCast AQI uses multiple hours of past data to show the current hour on the AQI scale.
Can smoke high in the sky affect my air quality?
Not always. EPA says satellite plumes include smoke high in the atmosphere that may not affect air near the ground. Ground-level monitors and sensors show what is in the air people breathe.