What AQI is safe for kids to play outside?

The short answer

An Air Quality Index (AQI) of 100 or less is the level where every chart read for this page sends all children out to play. Above that, the answer depends on the band.

At 101 to 150, recess still goes ahead under most written guidance. EPA's school sheet says it is "OK to be active outside, especially for short activities such as recess"¹. New York City says the same for activities under an hour². Utah is stricter. It keeps students with breathing symptoms, and sensitive students such as those with asthma, inside³.

At 151 and above, bring recess in. This is the band where the agencies disagree, and the next sections show why the indoor line is the better supported one. At 201 and above there is no disagreement. All three charts and one district policy move all outdoor activity indoors¹²³⁷.

What the AQI number means

The AQI is EPA's scale for how clean or dirty the outdoor air is. It has six bands, each with a color and a level of health concern⁴. An AQI of 100 generally matches the short-term national air quality standard for that pollutant. EPA says values at or below 100 "are generally thought of as satisfactory". Above 100, the air is unhealthy, "at first for certain sensitive groups of people, then for everyone as AQI values get higher"⁴.

Four details decide how a school should read the number:

• One number, five pollutants. The AQI covers ozone, particle pollution, carbon monoxide, nitrogen dioxide and sulfur dioxide. The number you see is the highest of them, called the main pollutant⁴. EPA's school sheet deals with the two it names: ozone and particle pollution¹.
• PM2.5 means fine particles. These are particles under 2.5 micrometers across. EPA says they cause the greatest problems because they get deep into the lungs⁴. AirNow's Fire and Smoke Map shows smoke as PM2.5 readings⁴.
• Children are a sensitive group. EPA lists "children, including teenagers" as a sensitive group for ozone and for particle pollution⁴.
• The current reading moves. AirNow's current AQI is the NowCast, worked out from hourly monitor readings. EPA says that even when the day's forecast is poor, "there may be times during the day when air quality is OK for outdoor activity"⁴.

Three agencies, side by side

Here are the three charts, band by band. EPA's sheet is the federal one for schools. New York City's covers child care, schools and camps. Utah's reads fine particles only. It counts them in micrograms per cubic meter of air (µg/m3). It marks 35.4 as AQI 100 and 55.4 as AQI 150³.

A school district in Idaho writes the same split into policy. Kimberly School District allows outdoor activity at 101 to 150 only with extra rest periods. Over 150, "all students and staff will remain indoors"⁷.

Which line is right at 151

Two answers circulate for the Unhealthy band. One says recess can go on if play is short and light. That is EPA's 2014 school sheet and New York City's 2023 sheet¹². The other says everyone comes in. That is Utah's sheet and Kimberly's policy³⁷.

The indoor line is the better supported one, for three reasons:

• EPA's own AQI guide treats children as sensitive. For fine particles at 151 to 200, it tells sensitive groups to "consider rescheduling or moving all activities inside"⁴. The school sheet itself says children are "more sensitive than adults to air pollution"¹, yet in this band it asks only for more breaks and lighter play.
• Everyone is affected in this band. Caring for Our Children is the national child care standard. It says that at 151 to 200 "everyone may begin to experience some adverse health effects"⁶.
• Smoke points the same way. EPA's school sheet itself says to "limit outdoor activity when there is smoke in the air"¹.

The softer line persists because its logic is sound as far as it goes. EPA explains that more pollution enters the lungs when a child breathes harder. Shorter, lighter play cuts the dose¹. But EPA's newer AQI guide asks more of sensitive groups on a particle day than the 2014 sheet asks of schools⁴.

Ozone is the one place the guide leaves room. At 151 to 200, it tells sensitive groups not to do "long or intense" outdoor activities. It says to plan them for the morning, when ozone is lower⁴. So on an ozone day, a short, light morning recess fits EPA's wording. On a particle day, it does not.

The 2024 change to the scale

Utah's sheet dates from July 2016³. EPA changed the AQI breakpoints for fine particles in 2024, effective May 6, 2024⁵. A breakpoint is the particle level where the AQI category changes.

The two numbers Utah's sheet turns on did not move. 35.4 µg/m3 is still the top of Moderate (AQI 100), and 55.4 is still the top of Unhealthy for Sensitive Groups (AQI 150). EPA kept those because it kept the 24-hour fine particle standard of 35 µg/m3⁵.

What did change is the top of the scale. Utah's chart puts AQI 300 at 250.0 µg/m3. On the current scale, AQI 300 is 225.4³⁴. That changes no Utah recess call, since every reading above 55.5 already keeps all students in. It matters for charts that act on the AQI number. A reading of 140 µg/m3 used to be Unhealthy. It is now Very Unhealthy, where EPA's and New York City's sheets move everything indoors¹²⁵.

One smoky morning, walked through

Suppose wildfire smoke drifts over a school. At 10 a.m., AirNow shows a current AQI of 165, with PM2.5 as the main pollutant. On the current table, 165 is Unhealthy, so the particle level is between 55.5 and 125.4 µg/m3⁴. Recess is at 10:30, for 20 minutes.

So the same morning splits two ways. Under this page's rule, the class stays in. Now suppose the smoke thins and the NowCast reads 140 by noon. That is back in the orange band. Under every chart above, a short recess can go ahead, and Utah would keep sensitive and symptomatic students in³.

Child care, babies and children with asthma

Child care has a national standard, but no number. Caring for Our Children says adults "should check the air quality index (AQI) each day". They then use it to decide whether it is safe for children to play outdoors⁶. It gives the reason: air pollution can contribute to asthma attacks in sensitive children. Over years it can contribute to permanently smaller lungs that work less well⁶. Which state rules name air quality is covered in daycare outdoor time requirements. The yard itself is covered in childcare playgrounds.

New York City's sheet is written for child care as well as schools. It says young children are more vulnerable than healthy adults². It adds that N95 or KN95 masks can cut exposure when worn correctly, by people age 2 and older². No source read here sets a separate AQI line for babies.

Utah names the sensitive students. They include children with asthma, cystic fibrosis, chronic lung disease, congenital heart disease, weak immune systems or other breathing problems. Parents, with their doctor's advice, should tell the school³. Children with asthma should follow their asthma action plans and keep quick-relief medicine handy, say EPA and New York City¹². Put the plans in the supervision notes for recess staff.

Indoor recess on a bad air day

Moving in does not have to mean sitting still. EPA says ozone is much lower indoors with the windows closed. So it is fine to keep children moving. For particles, indoor air is cleaner only if the building's heating or cooling system filters them and is "installed properly and well maintained"¹. EPA suggests jumping, skipping, sit-ups and push-ups, or cones, hoops and balls in a gym¹. Indoor play spaces covers rooms built for it, and how much outdoor play children need covers why the lost minutes matter.

Watch the heat at the same time. EPA warns that without air conditioning, staying in with the windows shut "may be dangerous" in extreme heat⁴. On a hot day, read this page with how hot is too hot for recess.

Where this answer stops

This page covers the outdoor air pollution the AQI measures. EPA says the AQI "does not apply to hazardous air pollutants, extreme heat, and other aspects of outdoor air"⁴. Pollen is not one of its five pollutants, so a high pollen count will not show up in it. Heat has its own cutoffs, and so does cold: see how cold is too cold for recess. Storms are a separate call, covered in lightning on the playground.

It is written for recess and short outdoor play. Sports practices and games run longer, and EPA and New York City are stricter about those at 101 to 200¹². A child's own asthma action plan, from their doctor, outranks any general line here. No source read here sets a safe number of minutes at each AQI. EPA's sheet says plainly: "There is no exact amount of time"¹.

The three charts and the Idaho policy are examples, not a survey. None of the charts is law, and the Idaho policy binds only its own district. Check your own district or licensing rules, which state recess laws and school playgrounds can help you find. For heat, cold, smoke and storms together, sun, UV and heat illness and first aid and emergencies cover what to do when a child gets sick outside.