Indoor Air Guide
What does your AQI number actually mean?
The air can look perfectly clear and still carry an AQI that affects how you feel. Here's how the 0–500 Air Quality Index scale works, what each band means for your body, and why "moderate" isn't the same as "fine."
AQI (Air Quality Index) is a standardized 0–500 scale that converts pollutant concentrations, PM2.5, PM10, ozone, and others, into a single number. 0–50 is good, 51–100 is moderate, and above 100 starts to affect sensitive groups. The catch: even a "moderate" reading around 69 can leave people with asthma or allergies with a tight chest, itchy eyes, or unexplained fatigue, moderate doesn't mean harmless.
The air looks fine. It isn't always. At a moderate AQI, people with asthma or allergies already feel it, and even healthy lungs are working a little harder than usual.
The 6 categories of the Air Quality Index
AQI is calculated from the pollutant with the worst reading at the time, usually PM2.5 or ground-level ozone. These are the standard EPA categories used across most air quality reporting.
"Moderate" doesn't mean harmless.
An AQI of 69 sits comfortably inside the "moderate" band, officially fine for almost everyone. But officially fine isn't the same as unnoticed.
At this level, people with asthma or allergies already feel it, a tighter chest, itchy eyes, a fatigue they can't quite explain. Even healthy lungs are working a little harder than they would on a genuinely good-air day.
You don't need a red alert to make a smarter choice. Skip the long run outside today; if you need fresh air, morning or evening, when traffic is lower and AQI tends to drop, is the better window.
What to actually do with an AQI reading
You don't need to memorize the scale, just know the three moves that matter most.
Morning or evening, not midday
AQI tends to drop when traffic is lower. If you need fresh air, that's the window, skip the long run when it's peaking.
Don't let outdoor air become indoor air
Above moderate, outdoor pollution infiltrates indoors fast. Close windows and rely on filtered indoor air instead.
Asthma, allergies, kids, older adults
If anyone in the home is in a sensitive group, treat "moderate" as your cue to check, not just "unhealthy" ratings.
BAVAMA tracks what AQI leaves out.
Outdoor AQI tells you about the air outside. BAVAMA tells you what's actually happening in the room you're standing in, PM2.5, CO2, VOCs, and more, measured directly.
- 1Direct indoor PM2.5 tracking, the pollutant that usually drives your local AQI number, measured where you actually breathe.
- 2Plain-language status, so "69" becomes "borderline, sensitive groups should be cautious today."
- 3A clear next step every time, close the windows, run the purifier, or go ahead and open up.
AQI, answered
It's technically "moderate," and moderate doesn't mean harmless. Most healthy people won't notice anything, but people with asthma or allergies can already feel it, a tighter chest, itchy eyes, or fatigue they can't explain. Even healthy lungs are working slightly harder than on a genuinely good-air day.
Below 100 is generally fine for healthy adults, and below 50 is ideal. If you're in a sensitive group (asthma, allergies, heart or lung conditions), be more cautious once AQI passes 100, and consider timing outdoor activity for morning or evening when traffic, and often AQI, is lower.
AQI is a composite score calculated from several outdoor pollutants (commonly PM2.5, PM10, and ozone), usually reported by government monitors for outdoor air. PM2.5 and CO2 are individual measurements you can track directly indoors, a home air monitor reports these directly rather than a full outdoor AQI composite, since components like ozone behave differently indoors.
Monitoring stations measure several pollutants, convert each to its own sub-index using EPA breakpoint tables, and report the highest sub-index as the overall AQI. That's why the "dominant pollutant" (often PM2.5 or ozone) can change from day to day in the same city.
Yes, once AQI passes "moderate," outdoor pollution starts infiltrating indoor air more noticeably. Keep windows closed, run a HEPA purifier if you have one, and save ventilation for when outdoor air quality improves.
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