I think I got this one. EPA regulates (outdoor) air quality based on particle counts. I am in a city that gets regularly spanked on our PM 2.5 counts. The PM 2.5 count to EPA regulated Air Quality Index (AQI) in repeated on this page:
http://data.fnsb.us/airquality/AQNearRealTime , FWIW I live kinda near the "oa" in Broadmoor towards the left side of the 'rectangle of death' aka non attainment area.
There are probably similar EPA regs for PM10 and so on, outdoor PM2.5 is the thing EPA is spending tax dollars on here.
David:
I had previously used the Dylos formula for calculating AQI from their meter (at your suggestion in our previous thread). This is the explanation on Bill Pentz's website:
http://billpentz.com/woodworking/cyclone/dylos.php
In essence, it is PM 2.5 = (Small Particles - Large Particles) /100
Now the units may be wrong here, and David please correct me if that is the case. I believe this gives the number in mcg/m3 which is the typical units for PM 2.5.
Alan
The next time I run my wide belt, I'll put both meters next to each other, and look at the readings.
- After I ask a stranger if I can pet their dog and they say yes, I like to respond, "I'll keep that in mind" and walk off
- It's above my pay grade. Mongo only pawn in game of life.
Yes, that formula provides a rough estimate of PM2.5 and the units are indeed mictogram per cubic meter. If you want to trudge through the math the assumptions are a particle diameter of 1.5 micron and density of 1.6 g/ml.
Obviously there's a lot of room for uncertainty when you have to assume an average particle diameter for a distribution that ranges over a 5:1 range. That's actually a 125:1 range for the mass per particle. Size distribution varies a lot for different materials and generating processes as well as distance from the source.
For more details on using particle counts to estimate PM levels see this paper.
Beranek's Law:
It has been remarked that if one selects his own components, builds his own enclosure, and is convinced he has made a wise choice of design, then his own loudspeaker sounds better to him than does anyone else's loudspeaker. In this case, the frequency response of the loudspeaker seems to play only a minor part in forming a person's opinion.
L.L. Beranek, Acoustics (McGraw-Hill, New York, 1954), p.208.
My old hero.
- After I ask a stranger if I can pet their dog and they say yes, I like to respond, "I'll keep that in mind" and walk off
- It's above my pay grade. Mongo only pawn in game of life.
The air quality agency for the Los Angeles region has done a lot of work testing consumer sensors against lab-quality equipment. They have evaluations for many popular models. http://www.aqmd.gov/aq-spec/evaluations/summary-pm
I was involved with a project a few years back where we decided to use purple air sensors, as much for their interface as for their accuracy/precision.
Found what appears to be the same product on Amazon:https://www.amazon.com/Digital-Quali...2319002&sr=8-3
Costs more, but free returns if you have Amazon Prime and you can avoid the spam from Banggood everybody is warning about.
I didn't buy it from Amazon since at the time it said "not in stock" and the projected delivery time was so long.
How long does it take to quit getting emails from Banggood? I clicked to get off their list but 4 days later I still get several promotional emails a day.
BTW, I didn't see anywhere I signed up for emails when purchasing. Maybe it was in their Terms of Service or Privacy notice (which I did read or try to) but clicking that was required for the purchase. Did I miss something or were they being sneaky?
JKJ
Last edited by John K Jordan; 09-22-2021 at 1:24 PM.
- After I ask a stranger if I can pet their dog and they say yes, I like to respond, "I'll keep that in mind" and walk off
- It's above my pay grade. Mongo only pawn in game of life.
At this point, is there a prefered air-quality measurement tool for the shop?
Are the purple air sensors useful for shop measurements?
(I'd bought a dylos years back, but it recently stopped working--shows all 0 after a few minutes)
Matt