What Counts as a Good AQI Number?

You open Aether and see a single figure — 42, 78, 164 — and want a straight answer: what is a good AQI number? The Air Quality Index is designed for exactly that question. It rolls complex pollution data into one score so you can decide whether the air is fine for a run, safe for kids to play outside, or better spent indoors.

Most countries use a similar 0–500 scale with colour bands. Lower is cleaner. The trick is knowing which band counts as good for you personally — because a moderate reading that is harmless to a healthy adult may be too much for someone with asthma.

What is a good AQI number on the standard scale?

Green and yellow — where most days should land

AQI 0–50 is Good (green). Air quality is satisfactory, and air pollution poses little or no risk for the general public. If you are asking what is a good AQI number for everyday life, this is the target — outdoor exercise, open windows, and normal activities are all reasonable for most people.

AQI 51–100 is Moderate (yellow). Air quality is acceptable, though unusually sensitive individuals — people with mild asthma, for example — may notice effects during long outdoor exertion. For many cities, a reading in the 60s or 70s is a normal, decent day.

Once you climb above 100, the air is no longer good for everyone. Sensitive groups should start adjusting plans; above 150, the general public should pay attention too.

When AQI is no longer good

AQI 101–150 (orange) is Unhealthy for Sensitive Groups. Children, older adults, and people with heart or lung disease should reduce prolonged outdoor exertion. Healthy adults can often still walk or commute, but hard training may wait.

AQI 151–200 (red) is Unhealthy. Everyone may begin to experience health effects; sensitive groups should avoid prolonged outdoor activity. AQI 201–300 (purple) is Very Unhealthy — outdoor exertion should be avoided. Above 300 (maroon) is Hazardous; everyone should minimise outdoor exposure.

These breakpoints align closely with WHO thinking on short-term exposure, though national agencies may use slightly different formulas. Your app shows the dominant pollutant driving the number — often PM2.5 in smoke or winter smog, ozone on hot afternoons.

What is a good AQI number for you personally?

Context beats a single threshold

A good AQI number for a marathon trainer differs from a good number for a toddler with bronchitis. If you are healthy, many coaches treat anything under 100 as workable for moderate runs, under 50 as ideal. If you are in a sensitive group, under 50 is the comfort zone and you should scrutinise anything above 75 before strenuous plans.

Duration matters. AQI 95 for a twenty-minute walk is not the same as AQI 95 for a two-hour football match. Route matters too — a good city average can hide bad air along a highway verge.

• Good for most people: AQI at or below 50.
• Generally acceptable: 51–100, with caution for sensitive groups.
• Adjust plans: 101–150 for children, older adults, and respiratory conditions.
• Limit everyone outdoors: 151+; postpone sport and heavy exertion.
• Emergency conditions: 201+ — follow local health advisories.

Using AQI as a daily habit

Check the number once in the morning and glance at the hourly forecast before afternoon activities. Compare PM2.5, ozone, and the overall AQI — the worst pollutant wins. Over time you will learn what a good AQI number looks like in your neighbourhood across seasons.

Aether shows live readings, pollutant breakdowns, and forecasts so you are not guessing from haze alone. Pair the index with how you feel — scratchy eyes, wheeze, or unusual fatigue on a yellow day are signals to take the number seriously.