What does one do with an air quality report?

I know I’m walking the line with putting this in GQ, but I feel that there must be a factual answer to why news stations do this.

Here in Paris, every morning, there is an air quality forecast that tells how good/bad the air will be that day. I think the same thing exists in LA.

My question, assuming the air is bad, what is one to do? I understand that when the weather is bad (rain, snow, etc.) one can prepare oneself by dressing accordingly, but what does one do with an air quality report? Stop breathing?

Should I by a mask?

For people with asthma or other respiratory ailments, a bad air quality report is an indication that they may want to stay indoors as much as possible or take other precautions when going outside.

An air quality report can help you make decisions about timing outdoor exercise – pick which days of the week you’ll go for a run, for instance.

If the pollutant is ozone (‘smog’), then you could also make sure you’re getting your strenous outdoor work done as early in the day as possible. Smog gets worse through the day, usually peaking late afternoon. Even for healthy people, high ozone can damage the lungs slightly – I’m not saying the damage is necessarily worse than the benefit of exercising, but why not minimize the damage as much as possible?
Masks won’t help for smog.
If the problem is pollen, a mask might help. Though air quality warnings aren’t that useful for hayfever, because it doesn’t matter how much total pollen there is, only how much of whatever pollen you’re allergic to.

Yeah, I thought it could also help people schedule outdoor errands and such.

interesting question though… if the air quality is poor, how long does that take to filter into various kinds of buildings?? I mean, we don’t generally live and work in airtight structures with their own oxygen replenishment/CO2 scrubbing units built in. Wouldn’t any bad elements in the air outside get inside soon??