AQI Detail Page
AQI 400: cigarette equivalent, interpretation, and what to do next
At AQI 400, a full day of exposure is roughly equivalent to smoking 18.2 cigarettes. The point of this page is not just the number. It is helping you decide how much of your routine should change.
AQI category
Hazardous
PM2.5 estimate
400.5
µg/m³
Daily equivalent
18.2
cigarettes / 24h
If repeated daily
546
cigarettes / 30 days
What AQI 400 means
Avoid outdoor exposure unless it is essential, and use layered indoor protection.
People with breathing or heart problems may need professional medical advice if symptoms worsen.
Exposure framing
1 hour: about 0.76 cigarettes.
2 hours: about 1.52 cigarettes.
24 hours: about 18.2 cigarettes.
7 repeated days: about 127.4 cigarettes.
Scenario guidance at AQI 400
These are the kinds of day-to-day decisions users commonly make from this reading.
Commute or errands
Avoid2 hours equals 1.52 cigarettes at AQI 400.
Delay nonessential errands and consolidate unavoidable travel.
Outdoor exercise
Avoid1 hour equals 0.76 cigarettes at AQI 400.
Skip outdoor exercise and wait for cleaner air.
Kids, school, or playground time
Avoid3 hours equals 2.28 cigarettes at AQI 400.
Keep children inside and use the cleanest indoor space you can maintain.
Sleeping with windows open
Avoid8 hours equals 6.07 cigarettes at AQI 400.
Seal the room as much as possible and run filtration continuously.
Why the estimate is credible
The site first converts AQI into an estimated PM2.5 concentration and then applies Berkeley Earth's cigarette-equivalence framing.
The estimate is most useful for comparing air-quality dose across times, situations, and repeated days. It should not be treated as a literal smoking-equivalence medical claim.
View next
Commute exposure planner
Use AQI to decide whether a daily commute is routine, cautionary, or worth changing.
Outdoor exercise risk guide
Translate AQI into a clear decision for running, cycling, or training outside.
Kids and school exposure guide
Plan school runs, recess, and after-school time when children are more sensitive than adults.
City planning pages that pair with this AQI
Use these as repeat-visit guides when the same types of air-quality questions keep returning.
Los Angeles AQI planning guide
Interpret LA air quality for commuting, outdoor exercise, and smoke-season decisions.
San Francisco AQI planning guide
Use AQI to decide on transit, neighborhood differences, and wildfire smoke response in the Bay Area.
New York City AQI planning guide
Interpret AQI for street-level exposure, commuting, exercise, and occasional smoke events in NYC.