You're standing on the curb of a house you might actually buy. The agent says “great neighborhood, great schools.” What they don't say: last August, the AQI here hit 187 for two weeks because of a wildfire 300 miles away, and your asthmatic 8-year-old would have spent every recess inside.
Air quality isn't the kind of thing real estate listings ever mention. But if you're moving across the country — especially with kids, a respiratory condition, or just a love of running outside — it's the difference between feeling great in your new home and quietly regretting the move every July through October.
Here's what “good AQI” actually means, and the questions to ask before you commit.
100K+
Estimated U.S. deaths per year linked to long-term PM2.5 exposure — most from heart and lung disease, not lung cancer.
Harvard T.H. Chan School of Public Health · 2022
The AQI scale, in real terms
The Air Quality Index (AQI) is a 0–500 scale combining ozone, PM2.5, PM10, carbon monoxide, sulfur dioxide, and nitrogen dioxide. The colors and ranges:
- 0–50 Good (green): Air feels clean. No restrictions for anyone.
- 51–100 Moderate (yellow): Fine for most people. Sensitive groups may notice it.
- 101–150 Unhealthy for Sensitive Groups (orange): Kids, elderly, asthmatics should limit prolonged outdoor exertion.
- 151–200 Unhealthy (red): Everyone should reduce outdoor activity. N95 if you must be outside.
- 201–300 Very Unhealthy (purple): Stay indoors. Run HEPA. Schools usually move recess inside.
- 301+ Hazardous (maroon): Health emergency. Common during major wildfire events.
It's not the average that matters — it's the pattern
Boise has a lower annual AQI average than Atlanta. But Boise hits AQI 150+ for 30–60 days during wildfire season, while Atlanta rarely exceeds 100. Two very different living experiences. When evaluating a city, ask three pattern questions:
- Spike days: How many days per year above AQI 100? Above 150?
- Seasonality: Are bad days clustered in summer (ozone), winter (inversions), or fall (smoke)?
- Trend: Is the city getting better or worse over the past 5 years?
Cities that look fine on a Tuesday visit:
- Salt Lake City — winter inversions trap PM2.5 in the valley for weeks
- Fresno / Bakersfield — central valley dust + ag emissions, year-round
- Portland / Seattle — clean most of the year, brutal during August/September smoke
- Phoenix — ozone alerts on most hot summer afternoons
- Denver / Boulder — front range brown cloud + wildfire smoke
Long-term PM2.5 — the quiet one to watch
AQI dashboards focus on today. But the health research is increasingly clear: it's the long-term average PM2.5 exposure — the air you breathe day after day for years — that drives heart disease, stroke, dementia, and pregnancy complications. The EPA tightened the annual PM2.5 standard from 12 to 9 µg/m³ in 2024 specifically because of this evidence.
If you're moving somewhere with annual PM2.5 averaging 12+ µg/m³, that's a number worth taking seriously, even if no single day looks alarming. Areas of concern include the San Joaquin Valley, parts of the Ohio River Valley, and downwind of major freight corridors.
What to actually do about it
You can't move the freeway. But you can make practical choices:
- Choose neighborhood over city. Within most metros, distance from highways, ports, and rail yards matters more than the city average. A mile of buffer often cuts PM2.5 noticeably.
- Invest in HEPA. One purifier per main living area, run 24/7 during smoke events. Cheap insurance compared to a respiratory ER visit.
- Tight envelope, MERV-13 filter. If you're buying or renovating, modern weatherization plus a MERV-13 HVAC filter is a real upgrade.
- Know when to stay in. Apps like AirNow, IQAir, and PurpleAir push alerts when local PM2.5 climbs.
Indoor air matters too — radon, VOCs, and gas stoves
Outdoor AQI gets the headlines, but you spend 70% of your time indoors. Radon (a colorless, odorless gas seeping up from soil) causes ~21,000 lung cancer deaths per year — more than drunk driving. Gas stoves release NO₂ at levels regulators wouldn't allow outdoors. VOCs from new carpet, paint, and furniture contribute too. Test for radon during your home inspection regardless of outdoor AQI.
Frequently Asked Questions
▸What AQI is considered unhealthy for children?
Kids start being affected at AQI 101 (Unhealthy for Sensitive Groups). At AQI 151+, everyone is affected — kids should limit outdoor play, especially anything with heavy breathing like sports. Schools in California, Oregon, and Washington increasingly close or move recess indoors above 150. If you have an asthmatic child, you'll want to know how often the city you're moving to hits that range.
▸What's a normal AQI in the U.S.?
About 70% of U.S. counties average under AQI 50 (Good) on a typical day. But 'typical' hides the spikes. The cities you should worry about aren't the ones with high averages — they're the ones with 10–40 days a year above AQI 100. That's where the real long-term health hit comes from.
▸Is PM2.5 worse than ozone?
PM2.5 (fine particle pollution) is generally worse for long-term health — it lodges deep in your lungs and crosses into the bloodstream. Ozone is worse for triggering asthma attacks and acute lung irritation, especially on hot summer afternoons. A city like Bakersfield gets hit hard by both. Phoenix is mostly ozone. The Bay Area is mostly wildfire PM2.5.
▸Should I avoid moving to a city with bad air quality?
Not necessarily — but you should know the pattern. A healthy adult can live in moderate-AQI cities with a HEPA purifier and an N95 in a smoke event. Families with young kids, pregnant women, asthmatics, or anyone with heart disease should weigh it carefully. Pollution exposure in early childhood is linked to lifelong lung capacity reduction, and that doesn't reverse.
▸How do I check air quality history for a specific neighborhood?
EPA's AirNow.gov shows current AQI and 7-day forecasts by ZIP. For multi-year history, EPA's Outdoor Air Quality Data tool (epa.gov/outdoor-air-quality-data) lets you pull annual stats by monitor. PurpleAir.com adds crowd-sourced sensors at much finer geographic resolution. For one-shot research on an address, a paid environmental report bundles all three with PM2.5 and ozone trends in plain English.
▸Does a HEPA filter really help with wildfire smoke?
Yes — when properly sized for the room and run continuously, HEPA purifiers cut indoor PM2.5 by 80–95%. The Wirecutter and Smoke Air Quality testing have confirmed this in real smoke events. The catch: cheap purifiers with HEPA labels often don't move enough air to keep up. Look for a CADR rating of at least 200 for a typical bedroom.
▸What about radon? Is that part of AQI?
No — AQI is outdoor air. Radon is indoor air, comes from the soil, and is the #2 cause of lung cancer in the U.S. after smoking. About 1 in 15 U.S. homes has elevated radon. Always include a radon test in your home inspection regardless of AQI, especially in EPA Zone 1 states like Iowa, Pennsylvania, Ohio, and Colorado.
Bottom line
A good AQI score isn't today's number — it's the pattern across a year. Before you commit to a city, look at spike days, seasonality, and the long-term PM2.5 average. Then pick a neighborhood with as much buffer from highways and industry as your budget allows.
Related: research a neighborhood before moving out of state, environmental risks before buying a house, FEMA flood zones explained, is flood insurance required in Zone X.
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