I looked into it a bit. The Purple Air sensors apparently have a large, but very consistent bias with wildfire smoke, so that they tend to give higher numbers than more sophisticated monitors. For that reason, I PERSONALLY use the LRAPA adjustment when I use Purple Air. Right now, for example, in Brisbane where I am, the unadjusted Purple Air numbers are in the 80s and 90s. LRAPA adjusted numbers are around 55. When I look out the window, the sky is blue and I can see the trees and brush on Mt San Bruno pretty clearly, with only a bit of haze in between. I would not hesitate to ride in this air - except I'm at work.
I bring this up solely for information! Everyone has to make the decision for themselves what AQI they're willing to ride in, and whether or not they want to use any adjustments for the Purple Air numbers. They're your lungs, after all! When SwimmerMike and I made the decision the last two Saturdays to put off the C&V ride, we used the straight numbers out of an abundance of caution and we'll continue using those for the group ride. Cross your fingers for this Saturday.