China Air Quality: What the AQI Numbers Actually Mean

TL;DR: 30-second version

China reports air quality as one number, 0 to 500, called the AQI. Under 100 is fine for most people. 150 is where you cut outdoor exercise. 200 or higher means stay in, and mask if you must go out. The catch nobody mentions: a 150 in China is not the same as a 150 back home, because the two countries use different formulas. We translate the whole scale below.

The short answer

The short answer: the AQI is a single number that tells you how polluted the air is right now, from 0 (clean) to 500 (very bad). You don’t need the science to use it, you need one mental chart: green and yellow are fine, orange means sensitive people take care, red means skip outdoor workouts, purple and maroon mean stay in.

What the numbers actually mean

China grades air under its national standard (HJ 633-2012), and the six tiers are simple:

• 0-50 (green): excellent. Best days of the year for a long run.
• 51-100 (yellow): good. Normal life, no thinking required.
• 101-150 (orange): lightly polluted. Kids, older adults and anyone with asthma should trim outdoor time.
• 151-200 (red): moderately polluted. We move workouts indoors and keep windows shut.
• 201-300 (purple): heavily polluted. Indoor day. Wear a mask if you have to go out.
• 300+ (maroon): severely polluted. Everything is indoors; an N95 for urgent errands only.

Why Beijing’s 150 is not LA’s 150

Here’s the detail most guides skip: China and the US EPA calculate the index from the same pollutants but with different breakpoints. In the US, PM2.5 at 35.5 micrograms per cubic meter scores AQI 100. In China, the same index of 100 only appears at 75 micrograms, roughly double. So an AQI of 150 in Beijing describes dirtier air than an AQI of 150 in Los Angeles.

The practical version: when your app shows a Chinese number, don’t bother converting it to home-town values. Trust the color instead, that’s the honest part.

One more thing: the US embassy monitor feeds that expats used to watch went quiet in 2024, so almost everyone now reads the official Chinese monitoring network or a third-party app. The list below is what we actually keep on our phones.

What to do at each level

Rules we actually follow, without obsessing:

• Under 100: nothing changes. Run, cycle, walk the kid to school.
• 100-150: sensitive groups ease off. Everyone else, carry on.
• 150-200: move the workout indoors. Close the windows. Turn on the purifier if you own one.
• 200-300: indoor day. If you must go out, wear an N95 or KN95, the thin blue surgical masks do almost nothing for PM2.5.
• 300+: treat it like a small blizzard. Mask for anything urgent and keep it short.

On masks: look for the N95 (US) or KN95 (China) label. Both filter around 95 percent of fine particles when they seal against your face, and a box of ten runs about 20 to 40 RMB in 2026. Cloth and paper masks are for politeness, not particles.

The three apps we actually use

• Air Matters: English interface, shows both the Chinese index and the US-style index, plus hourly forecasts.
• Blue Map (by the IPE institute): pulls straight from the official state monitoring stations, has an English mode, and shows station-level readings.
• Your phone’s built-in weather app: fine for a glance, same official data underneath.

Whatever you pick, check the number once in the morning with your weather, the way you check if it will rain.

Indoor air: the part you control

On bad days, indoor air is usually better than outdoors, unless you cook, burn incense, or smoke. A stir-fry without the range hood can push indoor PM2.5 above street level in under ten minutes, which surprises most people.

The cheap fix is a HEPA purifier sized to the room. For a bedroom around 15 to 20 square meters, look for a CADR around 200 to 300 cubic meters per hour; living rooms need bigger. Decent Xiaomi and Philips units run about 600 to 1,500 RMB in 2026, and a pocket PM2.5 sensor, about 150 to 300 RMB, turns “I guess it’s fine” into an actual number.

Two free habits: shut the windows when the outdoor AQI passes 150, and open them for ten minutes when it drops back under 100, because indoor CO2 builds up too.

Quick answers

Q: What AQI is unhealthy?
A: Most healthy adults are fine under 150. Above 150, cut outdoor exercise; above 200, stay in. Kids, older adults and people with asthma should trim outdoor time above 100.

Q: Is China’s AQI the same as the US AQI?
A: No. China’s formula reaches the same index number at roughly double the PM2.5 concentration, so Chinese readings run lower for identical air. Compare colors, not numbers.

Q: Do air purifiers actually work?
A: Yes, when they match the room size (check the CADR number) and you change the filter on schedule. We run ours on orange days and the indoor sensor drops quickly.

Q: Which mask should I buy?
A: N95 or KN95 with a good seal, about 2 to 4 RMB per mask in 2026 if you buy a box. The blue surgical ones block droplets, not fine particles.

Editorial review: EasternReset Team · Snapshot: 2026-09. Found an error? Email us.