# PM2.5 Monitor Question (particulates 2.5 microns or below)

## Main Question or Discussion Point

I got this generic china pollution monitor. When I turned it on. PM2.5 reads 49 ug/m^3 and PM10 reads 86 ug/m^3. It has vents at the back to measure the background levels. I don't know if my air levels is that high. I can't go to the mountains to test if it will read below 10 ug/m^3.

Anyway. Are PM2.5 (particulates 2.5 microns or below) or PM10 (particulates 10 microns or below) present in every cubic of air like it diffuses into the air for a specific neighborhood?

If you are exposed to PM2.5 OF SAY 49 ug/m^3, does it mean you breathe in all the particulates?

And lastly. Do you have any idea how to create a box where the particulates are suctioned out so the reading can be below 10 ug/m^3? I want to test if the unit can display a lower reading of PM2.5 and PM10. I can't ask the manufacturer since it's generic china unit. Thanks.

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davenn
Gold Member
2019 Award
When I turned it on. PM2.5
what is PM ? Particle Matter ? and if so does the manual specify what type ?

what is PM ? Particle Matter ? and if so does the manual specify what type ?
https://blissair.com/what-is-pm-2-5.htm
"
PM2.5 refers to atmospheric particulate matter (PM) that have a diameter of less than 2.5 micrometers, which is about 3% the diameter of a human hair.

Commonly written as PM2.5, particles in this category are so small that they can only be detected with an electron microscope. They are even smaller than their counterparts PM10, which are particles that are 10 micrometres or less, and are also called fine particles.".

The manual just says PM2.5. It is typical chinese manual that is very brief.

I just want to know how to create a box where all the particulate matter is suctioned out so I can test if the meter would read 2 ug/m^3 instead of ambient 49 ug/m^3. Is ambient meaning it is diffused everywhere in the city and we regularly breathe it in?

davenn
Gold Member
2019 Award
Is ambient meaning it is diffused everywhere in the city and we regularly breathe it in?
I would take ambient as being on a day without excessive air pollution ( you would understand
how levels change from day to day.)
And of ccourse, ambient levels in a city would be much higher than in the country

Maybe NOAA would have info on various levels that they would deem ambient for various USA locations.
If you are in a different country, go to your local atmospheric research institution

Dave

I would take ambient as being on a day without excessive air pollution ( you would understand
how levels change from day to day.)
And of ccourse, ambient levels in a city would be much higher than in the country

Maybe NOAA would have info on various levels that they would deem ambient for various USA locations.
If you are in a different country, go to your local atmospheric research institution

Dave
What kind of PM2.5 monitor do they use in the monitoring centers? I want to buy the most accurate ones available that can accurate measure PM2.5 levels. I can't find a reliable one at amazon which is for consumers. I need one for professionals.

davenn
Gold Member
2019 Award
What kind of PM2.5 monitor do they use in the monitoring centers?
I have no idea, I dont work in atmospheric research
Email the research centre in your country ( where-ever that is ) and ask them

And ... ohhhh.... if you want that level of accuracy, be prepared to spend $1000's so do you really need that level of accuracy ? why ? I have no idea, I dont work in atmospheric research Email the research centre in your country ( where-ever that is ) and ask them And ... ohhhh.... if you want that level of accuracy, be prepared to spend$1000's

so do you really need that level of accuracy ? why ?
I just want to have idea what is really the PM2.5 in my room. My china made meter reads 49 ug/m^3 while my air purifier built in pm2.5 meter reads only 12 ug/m^3. I just want to know what is the case. All wants to avoid pollution, just normal health concern, that's all.

davenn
Gold Member
2019 Award
. My china made meter reads 49 ug/m^3 while my air purifier built in pm2.5 meter reads only 12 ug/m^3. I just want to know what is the case.

Tho I'm not much of a fan of electronics from China, in general, they test gear does work well
And with that said, I would probably trust their meter that you have to be more accurate than
a basic air purifier that probably only gives an approx. reading and probably isn't even calibrated

D

Tho I'm not much of a fan of electronics from China, in general, they test gear does work well
And with that said, I would probably trust their meter that you have to be more accurate than
a basic air purifier that probably only gives an approx. reading and probably isn't even calibrated

D
I bought the unit above because it has CO2, TVOC and HCHO detector too and I'm just curious what is the level in my room.

Why is the CO2 (carbon dioxide) about 547 ppm? I read this is the normal reading elsewhere too even outdoor. But why do we have constant ambient of carbon dioxide in the air?

Also when I tried to breathe out in the inlet of the unit. The TVOC (Total Volatile Organic Compound) gets high about 4 or 5 times. Does our breathe have VOC components??

Tom.G
But why do we have constant ambient of carbon dioxide in the air?
It is a natural part of our atmosphere, just as Nitrogen and Oxygen are. It is also a by-product of animal life. We breath in Oxygen, use it to process nutrition to generate energy, and exhale Carbon Dioxide as a waste product. It is also generated when organic stuff, like dead trees, decompose; it is emitted by volcanoes and when just about anything burns.

Why is the CO2 (carbon dioxide) about 547 ppm? I read this is the normal reading elsewhere too even outdoor.
For around 1,000,000 years the natural concentration stayed below 300 ppm. Then around 1850 or so, we Humans started to industrialize. All the new industry needed energy to make things, so we started burning stuff (wood, coal, oil) to get the energy. One of the major products of burning stuff is Carbon Dioxide. As a result the Worldwide Carbon Dioxide cencentration has risen from about 283 ppm in 1800 to about 412 ppm as of December, 2019, about a 45% increase.

Your local reading of 547 ppm is not especially unusual for being in a city, especially if you are in an industrial area or near a lot of traffic.

The PM2.5 is high at 49ug, probably from vehicle traffic (especially diesel) or industry. Any wildfires upwind from you would also drive the PM very high from the smoke. The national standard for acceptable PM2.5 here in the USA is 12ug. We have been below that for about 10 years now.

https://www.epa.gov/pm-pollution

https://climate.nasa.gov/climate_resources/24/graphic-the-relentless-rise-of-carbon-dioxide/

Cheers,
Tom

sophiecentaur
Gold Member
I can't go to the mountains to test if it will read below 10 ug/m^3.
Perhaps a tent made out of wet bed sheets on a table top that's been washed down (or in the bath??) would give you a pretty clean temporary atmosphere. Experiment and see just how low your reading will go.
Very hard to calibrate anything, I would expect.

Perhaps a tent made out of wet bed sheets on a table top that's been washed down (or in the bath??) would give you a pretty clean temporary atmosphere. Experiment and see just how low your reading will go.
Very hard to calibrate anything, I would expect.
I think something is wrong with the unit above. So I am in the process of buying another pm2.5 monitor, a $149, that uses laser. The original above uses DART electrochemical sensors. But for measuring PM2.5 or PM10. I don't think DART can do that. Perhaps it uses simple light scattering techniques only. The second$149 pm2.5 monitor uses laser in measuring the particles (Laser Egg).

I can't find the exact technical details of how the laser can measure the PM2.5 or PM10, and I have been googling since yesterday.

Anyone knows how the laser counts the particles? Perhaps this can be moved to the Electrical Engineering since I want very technical details of how the technology of laser counting in general pm2.5 monitors is implemented. So want to see list of all techniques.

sophiecentaur
Gold Member
Anyone knows how the laser counts the particles?
An instrument called an eriometer (mind the spelling because Google just won't believe you got it right!!) uses monochromatic light to determine the diameter of particles in suspension. It works on the diffraction pattern of the particles. If you know the diameter, you have the area and that will give you the density of the particle distribution. Of course, if you have a mixture of particles then it's not simple because you see a whole range of diffraction patterns.

I would have given you a link but I could only find historical references to the work of Young and his generation. Have a Google search and you may find something that gives details. The technique is used all over the place.

An instrument called an eriometer (mind the spelling because Google just won't believe you got it right!!) uses monochromatic light to determine the diameter of particles in suspension. It works on the diffraction pattern of the particles. If you know the diameter, you have the area and that will give you the density of the particle distribution. Of course, if you have a mixture of particles then it's not simple because you see a whole range of diffraction patterns.

I would have given you a link but I could only find historical references to the work of Young and his generation. Have a Google search and you may find something that gives details. The technique is used all over the place.
I want to see actual implementation or schematic of it in actual devices. I'm familiar with young as the double slit experiment has been mentioned countless of times everywhere.

The following doesn't use laser, i want to see illustration involving laser:

sophiecentaur
Gold Member
Young knew about a lot more than his double slits. Have you actually read up on the eriometer?
PS Young did not use a laser. Edit: The light from a laser is not too different from light from the sort of source Young would have used (probably filtered sunlight). The advantage of a laser as a source is that it can be cheap and with a high intensity for a well defined wavelength. Is there any other relevant difference that you can think of?
PS the method of particle size separation in the above diagram is pretty smart and very convenient. I wonder how well it deals with particles of different densities.

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After days of analysis. I opted to get a separate Pm2.5/10 monitor based on the Plantower PMS5003 sensor: http://aqicn.org/sensor/pms5003-7003/

Now I'm looking for the best sensors to detect TVOC, HCHO and Co2. Amazon gave me until Feb 22, 2020 to receive the original multi detector. So I have a week to learn about better TVOC detectors. The one I have now is based on the china made DART Electrochemical sensors (see below). Problem with it is if I blow a breath into the unit inlet. All Co2, TVOC, HCHO suddenly increases 5 times. My breath sure doesn't contain VOC (Volatile Organic Compound) or HCHO (formaldehyde), does it?

Theoretically, how can the sensors detect the Volatile Organic Compound anyway? quantum tunnelling?

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I returned the unit in post #1 because it is quite inaccurate and got 2 more accurate ones.

Is anyone familiar with different sensors used pm2.5 monitors?

After returning it, i ordered the Laser Egg which is based on the Plantower 3003 but Amazon didnt send it for days so i changed my mind and got the Dylos instead. These are reviewed in:

https://smartairfilters.com/en/blog/how-accurate-are-common-particle-counters-comparison-test/

After some reading i found out a cheaper product from china (\$40) has the more latest Plantower 5003:

Now running them together.

This is the right one in another location shown so you can see the labels:

Some puzzles. The PM 10 in the right device is higher than its PM 2.5 while in the Dylos. The bigger particles (the right number on the display) are lesser. What sensor and principle produces more accuracy? Please check these sensors data.

https://aqicn.org/sensor/pms5003-7003/

http://billpentz.com/woodworking/cyclone/dylos.cfm