Is ozone 172 normal?

Not normal. Ozone index is considered as normal level between 0 and 50, moderate pollution level between 50 and 100, and serious pollution level over 100. Ozone 172 has reached the level of serious pollution, so it is not normal. Ozone index is an index used to express the concentration of ozone in the air, and the specific ozone index standard will change with the change of region, season and weather.