Interpreting Dylos 1100-pro readout questions

[Scott Winners]

I can't decide if I should get a hotel room tohight or stay home. I _think_ I can stay home.

I did find this article online: https://aqicn.org/experiments/what-is-the-dylos-monitor-actually-measuring/

And I read Bill Pentz' page: https://billpentz.com/woodworking/cyclone/dylos.php

I think that means my PM2.5 count ( I prefer to work in micrograms per cubic meter if that is all right with you) is 1.05 or maybe 1.3 and my PM10 count is about 0.26? Yes? No? I am not very smart. I think I have pretty clean air. This is at the side table next to my recliner chair in the same room as my wood stove loaded about 15 minutes before.

Pic one is the Dylos readout, the second is an EPA funded outdoor airquality array about 4 miles from my house.

Thanks

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[Scott Winners]

This is about an hour after loading the wood stove, roughly enough time for my filter box to get about 2 passes at all the air in the volume of the house ass/u/me-ing perfect circulation.

[Alan Lightstone]

Scott, those numbers are great, and your math is correct. My typical numbers of small particles in ambient air with my Dylos are about 500 (I can't remember what the typical larger particle counts in ambient air are.) In my workshop, my personal rule is that the air cleaners get turned on, and I wear a respirator when the small particle count exceeds ambient air, so 500. The vast majority of people reading this have worse PM 2.5 numbers than you right now.

I would have to keep both (or all 3) air cleaners on for probably about an hour to reach those numbers.

It also looks like your air cleaner is working very well. Lowering the particle count while the wood stove is producing particles is fantastic.

Stay home. I just read an article that the atmospheric river might give the Chugach mountains 12 FEET of snow:eek:

And pat yourself on the back. You've done a good thing with that air filter.

And there are worse places to be living and breathing the air than Fairbanks, right now. Lovelock, NV has an AQI of 168 this morning. Squaw Valley, CA is at 155. And Lahore, Pakistan wins the global award with an AQI of 397. The outside air in Fairbanks this morning is 36 (PM 2.5 of 8.7), so a good day there. The wind is coming from Canada.
Ah, those Canadians. ;)

Mine, on the Gulf of Mexico is AQI of 26 outside (PM 2.5 of 6.4), 0 inside.

www.iqair.com is a good resource for finding the AQI and PM 2.5 counts near your neighborhood. https://www.iqair.com/us/air-quality-map?lat=27.7858&lng=-82.74&zoomLevel=10&placeId=i8igFrtTEyq4NBKwK

The one I chose in Fairbanks is 147 Clay St. No clue where that is in relationship to your home, but there are quite a number of measuring sites in Fairbanks. Just 2 in my whole county of about 1 million people. I wonder why that is.

[Scott Winners]

Thank Alan. I am very glad David talked me into also buying the $60 particle counter, it should be here tomorrow. My numbers are, I think, shocking low, and I partly wonder if my Dylos didn't get knowcked out of calibration on the trip up here. My Dylos counts did go up when I baked a loaf of bread on Saturday, and again when my wife oven roasted some vegetables on Sunday, but I am routinely seeing counts like 40 small and 3 large first thing in the morning before loading the stove.

Fairbanks has all those sensors becuase of wintertime temperature inversions, we can go weeks at a time with AQIs in the 125-175 range with PM2.5 as the controlling pollutant. The "NCore" sensor is the one closest to my house, but I am upwind of it.

Will revisit Wednesday.

[Alan Lightstone]

Bring it into your shop and sand something. You’ll know soon enough.

[Doug Garson]

Currently the AQI in Vancouver is 45 and Richmond, part of Metro Vancouver to the south and closer to where I live is 60. My shop meter is reading 7. I haven't been working in the shop for a few days as I'm getting our garden pond ready for winter. Not sure how accurate my shop meter is, not a Dylos, but it does trend in the right direction.

[Scott Winners]

Currently the AQI in Vancouver is 45 and Richmond, part of Metro Vancouver to the south and closer to where I live is 60. My shop meter is reading 7. I haven't been working in the shop for a few days as I'm getting our garden pond ready for winter. Not sure how accurate my shop meter is, not a Dylos, but it does trend in the right direction.

Coverting particle counts to AQI is a bit of a bother. I noticed this weekend an outdoor PM2.5 count of 4 micrograms per cubic meter = AQI of 17. I don't have a conversion table handy.

[Scott Winners]

Hopefully David Morse will be along directly to clarify.

Doug's reading of "7" has no units on it so it could be particles per cubic foot or micrograms per cubic meter, possibly milligrams per cubic meter (seems unlikely) or a dimensionless AQI number.

I _think_ and Alan seems to be confirming on a Dylos calibrated for 0.5 and 2.5 the small particle count divided by 100 is a pretty good approximation of PM2.5 in micrograms per cubic meter that can then be stuck in an online calculator like this one:

https://www.airnow.gov/aqi/aqi-calculator-concentration/

to come up with an AQI index. It seems like 12 micrograms per cubic meter of PM2.5 converts to AQI = 50, the top end of the 'good' zone, where a PM2.5 concentration of 6 micrograms per cubic meter gives an AQI of "25", the top end of the excellent zone.

[Scott Winners]

An my thing came in today. Friday and Monday deliveries suggests my two counters came up from Seattle on two different container ships, and then rode the same rails up to Fairbanks on 2 different trains, blah blah. I am especially fond of the little red zero in the bottom right corner. The three green zeroes will give me an opportunity to say "Hapy happy happy" to my youngest daughter in the Duck Dynasty accent that will cause her to squeal.

[Doug Garson]

Looks like you bought the same one as I have. The 7 reading was the bottom right hand reading which is labelled AQI PM2.5. It will be interesting to see a comparison between the Dylos and the cheaper meter.

[Scott Winners]

Looks like you bought the same one as I have. The 7 reading was the bottom right hand reading which is labelled AQI PM2.5. It will be interesting to see a comparison between the Dylos and the cheaper meter.

Excellent AQI is 0-25. 0 is most excellent, 25 is still but just barely excellent, and your controlling pollutant, the one driving your AQI was PM2.5 in that moment. Even the EPA says your particles excellently controlled.

I look forward to collecting a definitive data set. I have seen some comparisons of the Dylos versus the $60 counter but have not been enamored of the size of the data sets used for comparison.

[Doug Garson]

My AQI may be excellent but the Vancouver reading of 45 while stated as good by iqair.com is apparently 1.1 times the WHO annual air quality guideline value so I guess it depends on who (not WHO), you are using as your reference value.

[David L Morse]

Both the Dylos and the Plantower (manufacturer of the sensor) are particle counters and it's appropriate to compare the particle counts, especially since the Dylos counter doesn't provide PM estimates.

The Plantower sensor bins the counts into six separate ranges, the Dylos into two. Fortunately two of the Plantower bins are the same as the Dylos, >.5 and > 2.5 so we can compare those. One problem is that the Dylos reads in Imperial units while the Plantower is metric. To convert, simply multiply the Plantower readings by 2.8.

Using the numbers in the image below you would compare 2.8 x 3490 = 9772 and 2.8 x61 = 171 to the two Dylos numbers. Agreement within about 20 or 30 percent I would consider good. Looking forward to the data!

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[David L Morse]

A particle counter displays it's measurements as number of particles GREATER in size than the reference value. So, for example, if the 2.5µm channel on the Dylos reads 26, that indicates 26 particles in .01 ft³ that are larger than 2.5 µm. It does not mean 26 particles of 2.5 µm size as there are really none that exact size.

A PM value indicates the total mass per cubic meter of particles LESS THAN the indicated size. So, for example, a PM2.5 of 35 means the total amount of material smaller than 2.5 µm is 35 gram per cubic meter.

PM values are cumulative upwards, like stalagmites. PM10 > PM2.5 > PM 1.0. PM10 includes PM2.5 which includes PM1.0 Counts are cumulative downward, like stalactites. (N>10) < (N>2.5) < (N>1.0) etc. N>1.0 includes N>2.5 which also includes N>10.

You're never measuring particles of a certain size. It's either particles greater than or less than that size.

[Scott Winners]

Using the Bill Penz (Dylos)/100 = PM in mcg/m3 I don't have good agreement. The two meters I have do agree pretty well between PM 2.5 @2.0 to 7.0 mcg/m3, otherwise the Dylos reads higher than the Plantower below 2.0 mcg/m3 and the plantower reads about double the Dylos above 7.0 mcg/m3. Given Bill was looking at wood dust and I am looking at wood smoke I am OK with a different conversion.

(Plantower) x 2.8 = Dylos +/- 30% fits my data even worse.

I ordered 3 more of the plantower today, and have an email in to Dylos as well. I want to get another Dylos with the USB port on it so I can import directly to eXcel. Once I have all five meters stacked up I will once again accidently on purpose spill a couple gallons of smoke out of the loading door - at least three hours before my wife gets home.

I found several journal articles online comparing Dylos to high dollar mass meters, favorably, I just need to find a conversion that fits my data after the six way shoot out. It would be very reassuring to me if the two Dylos's are in good agreement during/after the next smoke spill.

I am not looking for high precision from the Plantowers, but they are cheap and easy to operate. If the average plantower is showing AQI = 0 anytime real PM2.5 is 6.0 (or less) mcg/m3, and wakes up between 6.0 and 12.0 mcg/m3 it will be adequate to alert Joe Homeowner to get something done before the PM2.5 count exceeds 12 mcg/m3. My target beneficiaries are young couples say 20-30s with young kids at home and not a lot of extra money laying around. If the filter system works good enough they would not have to buy a particle counter to relax.

[David L Morse]

Using the Bill Penz (Dylos)/100 = PM in mcg/m3 I don't have good agreement. The two meters I have do agree pretty well between PM 2.5 @2.0 to 7.0 mcg/m3, otherwise the Dylos reads higher than the Plantower below 2.0 mcg/m3 and the plantower reads about double the Dylos above 7.0 mcg/m3. Given Bill was looking at wood dust and I am looking at wood smoke I am OK with a different conversion.

(Plantower) x 2.8 = Dylos +/- 30% fits my data even worse.



Keep in mind that the PM2.5 calculation from Dylos particle counts is only a rough approximation. It's based on an "average" particle size of 1.5 micron and an assumed particle mass density of 1.3 g/ml. With only two channels of size resolution you're trying to estimate an average particle mass out of a 125:1 range (mass varies with the cube of dimension). The Plantower sensor has four channels, including a 0.3 micron count, and uses a proprietary algorithm empirically tuned to industrial pollution in China to estimate PM numbers. I would expect the Plantower PM2.5 reading to have better agreement with your official monitoring station than the Dylos calculation.

Plantower x 2.8 / Dylos applies ONLY to 0.5 and 2.5 COUNTS, not PM values.

Also, neither the Dylos nor the Plantower are show raw counts. Those numbers are scaled from the actual analog pulse counts. At very low counts don't expect much correlation. There's a lot of noise in those numbers.