Ooohhh, That Smell: Arduino Monitors Air Quality

According to [Dr. Tom Lehrer’s] song Pollution, “Wear a gas mask and a veil. Then you can breathe, long as you don’t inhale!” While the air quality in most of the world hasn’t gotten that bad, there is a lot of concern about long-term exposure to particulates in the air causing health problems. [Ashish Choudhary] married an Arduino with a display and a pollution sensor to give readings of the PM2.5 and PM10 levels in the air.

The sensor uses a laser diode and a photodiode to detect and count particles, while a fan moves air through the system. If you aren’t up on pollution metrics, PM2.5 is a count of very fine particles (under 2.5 microns) and PM10 is a count of particles for 10 microns. You can find a datasheet for the device online.

One thing to note is that the sensor has a finite lifespan. The datasheet claims “up to” 8,000 hours. If you ran the sensor continuously that’s not quite a year, so you might want to be judicious about how often you light up the device.

This isn’t the first time we’ve seen this particular sensor. If you want to find the exact source of a pollutant, consider this build.

26 thoughts on “Ooohhh, That Smell: Arduino Monitors Air Quality

    1. Yeah, I read the title and thought … yeah right and my DMM measures Neutrinos.

      The manufacturer calls this sensor a dust sensor.

      In the data sheet (from the manufacturer) it’s called “Laser PM2.5 Sensor”. The additional datasheet (which includes) serial commands for other functions) is called “Laser Dust Sensor Control Protocol”

      There is this note in the datasheet “Scope of application Detector of PM2.5;Purifier”

      Then there are the sellers who add “Air Quality” and call it and “Air Quality Dust Sensor” which is bending the facts already.

      Then others call it an “Air Quality Sensor” which is completely untrue.

      Now HAD throws another misrepresentation into the confusion with “exposure to particulates in the air causing health problems”.

      it’s like “Oh, Oh, My hand is hurting so much” and getting the response “Well perhaps you may consider taking out of that fire”

      You CAN see dust. By the time it get so dense that it’s causing you respiratory difficulty it’s highly visible so you don’t need this sensor to tell you that.

      Granted: This sensor will detect particles a little finer than your average dust (approx PM2.5 to PM10) but it really doesn’t have the resolution to measure those things that are bad for your HEALTH.

      Those things that have the potential to compromise health are things like volatile compounds (including organic) and chemical/biological toxins. Most of these are in the range of 10nm to 600nm or 0.01um to 0.6um. That is far below the range of this sensor.

      I actually like this article and the project itself and it is useful for some things but …

      Let’s not call it something that it IS not. Lest I will have to my weegee (ouija) board and voodoo doll with me when I visit HAD.

      1. At the risk of sounding pedantic, you may be doing just what you’re describing here by misrepresenting what these sensors can measure. These sensors can measure particles which are smaller than 2.5 um. Take a look at the picture here ( to get an idea what we’re talking about. These particles are associated with different kinds of pollution and are small enough to get absorbed into our bodies.

        Although science is still getting to grips with all the ways this influences us, there’s no question prolonged exposure to quite modest levels is unhealthy. Quantities well in excess of what the WHO considers safe are invisible to the human eye, until you start getting to the extremes. See the WHO guidelines for the 24 hour and yearly mean exposure here (

        I’m currently evaluating the SDS011 and a couple of competing sensors for a project and I’m pleasantly surprised by what they can measure. While getting a fully accurate and calibrated number is complicated for a number of reasons, I am impressed by their ability to detect both small and large quantities of pollutants, with good linearity and excellent resolution. You can not only see the impact of events in your immediate surroundings, but can even differentiate between them. The more modern sensors bin the particles in ever more sizes, which may even allow for fingerprinting of the type(s) of pollutant if you do your homework.

        1. OK: Re: Info-graphic

          Items included:
          Sand (not recommended fo this sensor :)
          Hair: A lounge chair gives a better metric
          PM10: Dust, Pollen, Mold
          PM2.5: Combustion Particles, Organic Compounds, Chemicals

          Not included: smaller air-born items
          Viruses, Bacteria, Carcinogens (cancer causing), Toxins, Toxigens (genotoxic substances), Mutagens, Neurotoxins, VOCs, biotoxins, Mycotoxins.

          Unfortunately nobody told these types of “particles” that they have to fit within a range of sizes within one decade to make them convenient to measure and categorize.

          To say, for example, that organic compounds are detectable in the PM2.5 range is completely different from saying that all organic compounds are in the PM2.5 range. They are not.

          The same applies for much of the information you presented. While these things are true and they are in fact hazardous, that does not mean they are the “most” hazardous or even that they are “more” hazardous than other substances outside of the scope (and particle size) of the document.

          Now about the word “health” –

          I’m going to suggest that the person that has a cough and sniffle is actually doing better health-wise than the person that now biologically de-composing in the corner of the room (from CO poisoning) however this metric may suggest that air quality is better in the corner of the room.

          Ok this is obvious, what I am saying is that “health” is a very broad term.

          For example only 10% of cases of Motor-Neuron Disease (MND) are cause by the persons genetics. The other 90% are from “environmental” causes. These may or may not be air-borne.

          So what I am saying is that, if you want a good “picture” to draw “information” from with regard to “air quality” then you need to at the very least include “metrics” from PM0.1as PM2.5 will exclude a lot of the “information” that describes the “picture”.

          Thankfully, most manufacturers have a drop in PM0.1 unit to replace the PM2.5

          Most of the “really bad” stuff is below PM2.5 and in fact much of it is below PM0.1 but at least PM0.1 will give you a glimpse into the window.

          For air quality you really need to characterize the air. It’s not just about how much of what size particle. Its about “what environments” create the ratios of particle sized being detected.

          1. I have to admit that even after two lengthy posts I still don’t know what issue you perceive. You speak of measuring neutrinos using a multimeter, which is obviously a fantasy, while sensors measuring fine dust particles are not only feasible but real. They do not exhaustively measure every kind of pollutant you will encounter, but I doubt anyone would be naive enough to think this. To measure other pollutants or ranges you will need other sensors. My carbon monoxide alarms will not tell you about other pollutants and risks either, yet they’re definitely very useful to have around.

            These sensors can’t conclusively tell you the air quality is good, but they can tell you it’s not good. They provide a useful indication of particles between 0.3 to 10μm, with a convenient digital output of PM2.5 and PM10 values. These values line up beautifully with pollutant bins specifically indicated by the WHO as impacting our health. Numbers too high? Not good. It’s really not more complicated than that.

          2. Simple

            1) By no means whatsoever does this unit qualify to be called an “Air Quality Sensor”.

            2) Any reference to health or health effects are nothing more than speculative as it is totally beyond the scope of this device to metric any causative link.

          3. 1) These sensors measure particles in the air, specifically in the two bins described by the WHO in their ‘WHO Air quality guidelines for particulate matter, ozone, nitrogen dioxide and sulfur dioxid’ rapport. Note the ‘Air quality’ right before the ‘particulate matter’.

            2) The WHO rapport explicitly mentions particle source is not deemed to be a factor due to the adverse impact on health being similar world wide when similar particle levels are observed. Conversely, while these sensors shouldn’t be considered highly calibrated or scientific, they can provide the user valuable insights into unsafe air conditions and may help understanding the source of said particles. Coincidentally, it’s these very sensors various governmental agencies are fielding with the help of citizens to better understand particle pollution.

            WHO versus random internet guy. WHO wins.

          4. I guess you win!

            If you believe that anything published by WHO is the latest in their research then you need to understand that WHO doesn’t do any research internally. They just review documents that have already been pier reviewed by the scientific community. WHO documents are often the science from a decade or more before.

            If you believe that a PM2.5/10 sensor can also detect O1, NO2, SO2 then go right ahead and market it as an “Air Quality” sensor. I look forward to the law suits. Did you ever wonder why the manufacturer wont even call it an “Air Quality” sensor.

            So you win the prize of being that “random internet guy”.

            Might I mention that there are a large number highly intelligent and professionally educated people that visit this site.

            I personally learn a lot about other fields on this site.

            But I guess, with your attitude and naivety you also win the prize of being that member that is “not worth chatting to”.

            Enjoy your prize “winner”.

  1. This is an ineffective way to deal with that particular problem (even if it is a fun way to learn), because you would be better off just assuming that the air is full of pollution based on your location, then take steps to remove them. Electrostatic filters will remove a lot of the particles before the air has even hit a HEPA filter, then activated carbon for the volatile compounds. If that air has gone through an area with a lot of plants first, even better. But the only 100% effective filter is a cold trap and gas distillation setup, then you can drop 100% of the incoming air out of the gas phase and only keep the molecules you want, N2 and O2, but that is hideously expensive from an energy consumption point of view. Popping up from that rabbit hole again I guess the bottom line is that monitoring stations and air quality control are two very different problems and we should not confuse the two because what is the point of some neato device that just cries “Run away, run away!”, when there is nowhere to go?

      1. If you are on the move like that then your sensor, in its fixed location and microclimate, is just as likely to mislead you. Some other optical system looking at a distant target such that the beam path traverses the territory you will exercise in would be more informative. Pro tip, think before you snark on technical matters.

    1. And you can verify that your electrostatic/HEPA/carbon solution is effective because of…what? Guess work? Hopes and prayers? Assuming it working without monitoring is even worse.

      1. This sensor isn’t useful for that anyway. HEPA, by specification filters 99.97% of particles 0.3um (microns) or larger. This sensor is designed for particles of 2.5um or larger. Carbon filters trap even smaller particles then HEPA.

        1. Actually this sensor is designed to detect particles between 0.3 and 2.5 um. It is then extrapolating results for bigger particles. Carbon filters are usually used for volatile compounds, not for particles. Conventional filters are pretty efficient for particles below 0.01 um, they are captured using different mechanism than bigger particles.

      2. Well obviously more is better, that is self evident but that observation has no relevance to the original point made, furthermore the filter chain will always work better than nothing and it is safe to assume that. Seriously, stop and think about it for a while, if your budget is limited what choice do you make?

    2. This kind of pollution can change a lot when weather or other conditions change. Think of traffic increasing or decreasing, wind, rain and more. Having bunker style filters for your home or office is generally unfeasible, but mitigating the issue may be possible. Without knowing whether you need to act, that’s all moot.

      1. Bunker? Most HVAC systems should have HEPA these days, many have carbon filters too, and the electrostatic gear was common in professional darkrooms in the pre digital era, it ran 24/7 and worked perfectly.

        1. Apparently carbon filters in HVAC are a thing. It seems there’s an ANSI standard (ANSI/AHAM AC-1) which aims to measure air purifier effectiveness, which includes fine dust, pollen and tabacco smoke, although that’s for portable indoor purifiers, not HVAC.

          I’m very curious how (practically) effective either are removing smells and things like smoke or smog and how quickly they saturate.

          1. Yes the maintenance cycle would vary according to actual load and configuration, but having an initial electrostatic section that is self cleaning would greatly reduce the particulate matter reaching the other filter sections. Same with the VOCs if the air passes through and area with a lot of plants. So many variables, this means that you could do a very good or a very poor job of designing such a system depending on your skill and attention to details.

    1. Up to now, the Tom Lehrer song must relevant to my electronics exploits was “The Masochism Tango”. (If you don’t have any idea what we’re talking about, go to your favorite online tube on the interwebs and look up some classic comedy. You’re missing out.)

  2. This sensor is ideal for detecting pollen and wood smoke in the air outdoors. I have one on the bench ready for a test run. I am using an esp8266 Oak with MQTT to talk to home assistant. I figure it’s good enough to run it for five minutes every half hour during my waking hours to conserve the heater, fan and sensor.

Leave a Reply

