At what AQI level do you mask outside?

Yes, the particulates are quite large and are effectively blocked by an N-95 mask. I actually use the industrial ones, with the built-in exhalation port that makes it easier to breathe. This is a one-way valve, so it keeps out the bad air, but makes it easier to exhale. It also stays drier because much of the moisture from your breath is going out of the mask.
Picture of an example below - we but them by the dozen from a big-box home improvement store and look for the NIOSH certification on each mask.

That said, wildfire smoke is also irritating to the eyes. Wearing glasses, especially wraparound ones, and using soothing (not "redness-reducing") eyedrops helps. We really like the Optiva drops in individual vials that we can carry in our pockets and use as needed.

We get air quality alerts which include guidelines "for sensitive groups" or other categories.
It's easy to check air quality by zip code or city on AirNow.gov.
Here's one guideline.
https://www.cedars-sinai.org/newsroom/la-wildfires-mask-up-to-protect-against-poor-air-quality/#:~:text=An%20Air%20Quality%20Index%20level,problems%20could%20experience%20health%20effects.

Hi pacathy-
Have you seen the N95 by 3 M that is a three panel.??
I, myself, wear that one 90% of the time around people, doing house cleaning or in other environments that I feel the mask is needed.
Barbara

@pweg I never worry about whether I am the only person in a mask, whether it is for air quality or infection reduction. My daughter is a nurse, long Covid sufferer and has severe asthma. Her attitude is now mine. "What I do is for my health. If people ask I will explain, but I really don't care what they think."

My husband, neighbor and I wear masks on poor air quality days to mow and do year work I don't pay too much attention to the AQI - my lungs tell me if it is necessary. We always mask in airports and planes no matter what others are doing. Our Asian neighbors, who have much worse pollution in their countries, often mask in poor air quality - right down to little preschool children.

Sue, I don’t see the pictures of the mask that you mentioned, could you please send it?
Thanks!

I have tried twice and it won't go. Google "N95 respiratory mask"

Sue,

Based on your description in an your earlier post in this thread, I bought some of these masks on Amazon and am giving them a try to prepare for some upcoming travel I hope to do next month. I have not used them yet so I am not personally endorsing this model. But I thought it would be helpful if I uploaded a picture. Does this look like the kind of mask you use?