Air quality·ozone 90
ozone 90ppb
AQI 163
unhealthy · moderate

ozone 90 ppb — AQI 163

ozone at 90 ppb scores 163 on the US index, and the Korean grade calls it moderate.

The two systems disagree here

Concentration
90 ppb
US index (AQI)
163
US category
unhealthy
Korean grade
moderate
Concentration that makes 100
70 ppb

Same number, different verdict

A Korean forecast calls PM10 of 150 "bad", but the same value in the US index is 98 — still moderate. The other way round, PM2.5 of 40 has only just crossed into "bad" in Korea while the US index already reads 112, unhealthy for sensitive groups. Neither is wrong; they hold different rulers. Move country and the same air reads differently.

Nearby cells

85 ppb
AQI 150
100 ppb
AQI 188

Same pollutant, other concentrations

10 ppb
AQI 9
20 ppb
AQI 19
30 ppb
AQI 28
40 ppb
AQI 37
50 ppb
AQI 46
54 ppb
AQI 50
60 ppb
AQI 69
70 ppb
AQI 100
80 ppb
AQI 134
85 ppb
AQI 150
90 ppb
AQI 163
100 ppb
AQI 188
110 ppb
AQI 206
120 ppb
AQI 217
140 ppb
AQI 237
160 ppb
AQI 258
180 ppb
AQI 279
200 ppb
AQI 300

How to read this

  • On the left is the US index, on the right the Korean grade — the same concentration measured with two rulers.
  • Index values of 50, 100 and 150 are the boundaries; that is where the category name changes.
  • Forecast grades are usually daily averages, not the reading at this moment.
  • The cigarette figure is only for PM2.5 and assumes a full day of exposure.

Frequently asked questions

Q. How bad is ozone at 90 ppb?

163 on the US index, and moderate on the Korean scale.

Q. Do the two systems agree?

No — this is one of the places where one calls it moderate and the other calls it bad.

Q. What concentration would make the index 100?

70 ppb. This page is at 90 ppb.

Q. What is this pollutant?

ozone. The cigarette comparison is only applied to PM2.5.