I have two AirGradient units in my house in different rooms. They both detect 0 PM 2.5 (very rarely 1), but their PM 0.3 readings seem consistently high to me. One room never gets below 30, and currently is reading 156! The other occasionally gets as low as 5, but typically is over 20.
I can’t seem to easily find any good references about smaller particles. Do these numbers make sense, or are they clearly wrong? Is my house covered in asbestos or what?
The PM03 are particle counts and not ug/m3 as the other PM parameters.
So it’s normal that they are a lot higher.
Some questions:
I can see in my own house that either the two sensors are not calibrated the same, or one room has about 2x the amount of another room as a matter of course.
Have you tried moving both sensors to the same room?
In my house I consistently have a reading of 0 for pm2.5 but 0.3 is over 100 like yours.
To make sure, I brought my unit outside and saw a jump in numbers that made it similar to what AirNow shows for my area.
I haven’t tried moving the sensors to the same room yet… I’m planning on letting them exist in their separate rooms for a few days, and then swapping them. Not quite sure if that’s the best approach, and I’ll probably put them in the same room at some point to get a direct comparison between what they are reporting.
I do research regarding health effects of ultrafine airborne particles such as PM0.3 or PM0.1. It is a relatively young reseach field with many open questions. Scientists around the globe work on this emerging topic.
We know that the total mass of these particles is generally very low, whereas the total particle number is very high. The latter raises the question whether these particles pose a health risk. I am unaware of guidance from health or environmental agencies regarding PM0.3 or PM0.1, which is likely the result of the unclear health implications.
For scale: a 0.1 micrometer particle is equally long as 1000 hydrogen atoms. This comparison emphasises that we get close to the atomic level of matter, which makes research complex.
My gut feeling is the smaller the particle, the bigger the damage. So this is a field that needs better sensors and research for sure.
Already 2 microns is super small. As particle size decreases, the penetration efficiency into the lungs increases due to lower inertia. At some point, however, the particles are so small that brownian motion (= diffusion) dominates the depositon mechanism already before the particles reach the lungs. During my aerosol lectures, we learned that particles of around half a micron have the highest deposition rate into the lungs (see link below). I often hear people saying “the smaller the particles, the deeper they get into the lungs.” I am unaware of evidence to support this statement.
Personally, I am concerned about the mass of solid particles that reach my lungs and do not dissolve. In other words, I am worried about the mass of stuff in my lungs that accumulates and does not belong there. I am less worried about liquid particles or salt particles, as they may dissolve and do not (or less) accumulate.
On the other hand, I am concerned about ultrafine particles (= nanoparticles) reaching my lungs even if the mass is low. I am not necessarily concerned about my lung health, but more my general health as some of these particles likely enter my body and reach all organs with unknown implications. I normally measure 10’000 nanoparticles per mililiter of ambient “clean” air, but I have no clue where these particles come from. Neither do I know what they are or whether this number is just a normal natural background level or whether it is greatly polluted air. There is currently no clear evidence to say that these particles are a problem. Similarly, it is unclear whether they are not a problem. This field of research has just started to pick up momentum.
At the end of the day, we should not forget that particles at some point become atoms as they get smaller and smaller. Today’s instruments have lower size cut-offs of just a few nanometers - these particles are basically just a group of a few atoms. Are particles of that size a problem? Maybe not necessarily, but I assume it highly depends on what the particles are made from. There are definitely many research questions to be explored
It’s coming from catalytic converters and air traffic, I guess. For decades now.