HEPA filters work really well, it's worth just buying a few big ones and running them inside.

I got a few in CA because of the fires, but I run them all of the time and they work. I also have some AQI sensors and I can see the pm2.5 drop rapidly when the air filters kick in.

I don’t think it’s just particulates, Denver and the front range are routinely in the news for ozone issues [0]. I think that might be altitude related as well, though it may just be pollution. Den doesn’t quite make the top ten list of US cities with ozone problems, but it’s gotta be close [1].

[0] https://www.govinfo.gov/app/details/FR-2019-08-15/2019-17405 [1] https://www.usnews.com/news/cities/slideshows/the-10-us-citi...

I remember flying into Denver in the winter and seeing the inversion of just awful brown haze.

I cried for my lungs on that trip.

There are numerous studies on the myriad bad health effects of PM2.5.

The sooner we can transition to EVs, the better.

What's the PM2.5 contribution of automobile exhaust in a city like Denver, 5-10%ish?

I haven't found exact data for the contribution of ICE vehicles to PM 2.5 levels in Denver, but I've found some evidence of ozone [0] and carbon dioxide [1] contributions in Denver being around 30%, as well as contribution to PM 2.5 in "developed countries" being 25–30% [2].

Later edit: this EPA paper from 25 years ago [3] says "Vehicle exhaust was the largest PM 2.5 carbon contributor, constituting ~85% of PM 2.5 carbon at sites in the Denver metropolitan area".

[0] https://www.bizjournals.com/denver/news/2017/10/30/here-are-...

[1] https://www.denverpost.com/2020/01/19/colorado-air-pollution...

[2] https://publications.iarc.fr/_publications/media/download/37...

[3] https://www.epa.gov/sites/default/files/2020-10/documents/nf...

Also, the location of the pollution matters. The same pollutant can cause more problems released at ground level than from a stack.

Yes, I researched this for evaluating my son's previous school - there's a sharp drop off even from the 10-20-30 metre range to the 100-150 metre one, and things like wind directions certainly matter.

AusGov in their infinite wisdom built this primary school right on top of one of the busiest Melbourne streets for east-west through traffic, with long periods of bumper-to-bumper including the heavy trucks which are the worst. (You'd think cars in Aus have bad standards, but then there's the trucks.)

I'm willing to bet no-one even cared, as evidenced by the complete lack of air purifiers in the classrooms.

I wonder how much brake pads dust also contributes to PM2.5 and how much regenerative braking will decrease that effect.

Yeah, the smell that comes with it in the fall and winter is something else. I like Denver, but the brown cloud is no fun. It’s a downer coming out of the hills on I70 into the city and seeing it hanging there.

I gather it's better now, but flying in to LA in the 90s was similar. It felt like visiting God's ashtray.