Purple Air finally got back to me after a couple weeks. The "Support" email worked whereas the "Contact" email did not.
Did they seem good? Are you buying one?
Wow that took a long time, ordered in early August, received in mid-November. But after an initial delay, email contact was pretty good, I got questions answered, I got updates.
It was pretty easy to mount and register, first one in SW Idaho. Boise.purpleair.com. Four days later another one popped up on the map across town. The nearest active EPA PM2.5 monitor is 7 miles west.
It seems very sensitive. At first it was mounted on a post on the far end of our patio. One small cigar smoked in the interior of the patio on a slightly breezy afternoon, I didn't even see any smoke going towards the monitor, but it spiked. Also thought it would be far enough from the grill, about 25 feet. We grilled just a few jalapeno poppers, again, smoke going up, but the monitor measured a spike again. We just moved it to a far south corner of the house under the eaves where there is better ventilation. It's probably about 100 feet from our fire pit, but I have a feeling next time we have a fire we'll generate some New Delhi-level measurements.
PM2.5 seems to drive the AQI. Probably in the summer ozone will come into play, but ozone seems more predictable: hot day, lots of sun, lots of cars, diurnal ozone pattern. I feel like with the monitor I'll get a better idea of how bad the winter inversions and summer wildfire smoke are.