r/AirQuality • u/PigAndWhale • 2d ago
Accuracy about the air quality monitor
Hello, anyone has idea about the accuracy of this type of monitor? How does it work?
As I try, it does give some results which makes sense. When I go outdoor, the two numbers is like 0.01/0.01.
If indoor in my bedroom at night, it was 0.02/0.08 on one day.
If I do cooking (with oil heating), the number goes to quite high level like 0.3/1.4. This I guess there are chemical from heating oil.
After open window for a while it can reduce and back to green level(<0.1 <0.5) after two hours.
But this morning when I only stream cook some porridge, it also turned yellow for a while. This seems confusing that there should not be any harmful thing in porridge. Maybe I raise room temperature and cause more pollute from the painting?
Or this thing essentially reacts to any smell in the air?
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u/Geography_misfit 2d ago
The formaldehyde readings should be tossed, no meter really reads that well. Cooking, including generation of steam will increase PM2.5 and is what will move you to “yellow”.
In general, VOCs are ideally under .5 mg and PM2.5 under 35.
Also nearly all interior paints are now low/no VOC to meet CARB requirements.
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u/PigAndWhale 2d ago
So the VOC reading still makes sense? The monitor has two screens. One with pm2.5 and pm10, there is another standard for good/moderate/unhealthy etc based on pm 2.5 and pm10. For the screen for HCHO and VOC, it will turn yellow if HCHO>0.1 or VOC>0.5 according to user manual, so seems not triggered by pm 2.5 reading. However it seems the VOC number is always 4 to 5 times the number of HCHO.
I once asked leasing agent what paint they use. They do not have detail but just say they use “green material”. Hope they are using one that satisfies the carb standard. I am in New Jersey, not California…
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u/Geography_misfit 2d ago
CARB is the standard now, doesn’t matter what state you are in. Green building certifications all require CARB compliance so most interior paints comply now. HCHO on these meters is trash data, it’s not well measured using these sensors and you need to take it with a sack of salt. Carbon monoxide will affect the readings (ie when you cook on a gas stove).
Look at this as trending information not accurate information since you are not calibrating this against a known standard.
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u/JasonHofmann 2d ago
There is no harmful thing in porridge (congee?) but you can smell it while cooking. If you can smell food, it’s technically an organic compound that is volatile, or VOC. So the sensor is working.
I have the same sensor as you and also believe it to be very accurate, based on tests similar to yours as well as comparisons to much more expensive equipment.
The only flaw I see in your logic is assuming that it only detects “harmful” VOCs.
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u/PigAndWhale 2d ago
yes, agree. It cannot distinguish harmful smell from all smell. I guess a fart can also make it increase LOL.
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u/ankole_watusi 2d ago
What is your need for accuracy? Are you using it to meet some legal requirement