# Are there any cheap air quality sensors? [closed]

I have checked sparkfun and some other websites. It seems that there is no air quality sensors available in the market.

I would like to monitor PM2.5 and PM10. Are there any suggestions?

• PM10 is 10 micron particulate matter. PM2.5 is 2.5 micron particulate matter. You should mention that you are specifically looking for air particulate measurement sensors. There are a lot of different ways to measure and quantify "air quality". Nov 26, 2011 at 6:54

To detect dust, there is Sharp GP2Y1010AU0F, see http://www.watterott.com/de/Sharp-GP2Y1010AU0F-optischer-Staubsensor

It is cheap, measures particulat matter in air by reflection. But it has a huge drift, and it is hard to interpret small readings, but it worked for me up to a point. It is also not particularly sensitive - a minimum of $0.1 mg / m^3$ is quite a lot of dust. But for the price, it is certainly worth a try. And you must read the datasheet, of course.

Problem is, if you measure around humans, the amount of big particle dust (the kind you see blinking in the sun) is abundant, and it becomes even harder to measure fine dust. To measure fine dust, which settles way slower than the big stuff, you will have to do a measurement while you are away.

If you want to measure only the fine dust, you will have to filter that out first, and measure the particulate mass in the filtered air. That is probably not going to be cheap.

I've used some gas sensors from Futurlec with some success - at the very least they are really easy to interface with. I don't know what PM2.5 or PM10 means, but here are a couple of links:

It's a rather specialised field, as you know.
Something like this may make it easier to "do it yourself".

Size selective inlet for manual separation. Calibration could be "interesting". No electronics here - but lots of scope for using them for control.

They say:

• Ambient air is drawn into the size-selective inlet at a constant volumetric flow-rate of 1.13m3/min (67.8m3/h) for both the PM10 and PM2.5 inlets. To achieve this, the HiVol 3000 uses a true volumetric flow-rate controller (via temperature and pressure compensation of a mass flow sensor.)

The size selective inlet (SSI) uses the principle of cascade impaction to seperate particulates based on size. The particles in the air are accelerated through multiple acceleration nozzles. Particles larger than the specified 2.5 or 10 µm cut-point gain sufficient momentum to cause impaction onto a greased collection shim where they are trapped. (The collection shim should be periodically cleaned and re-greased.) The PM10 or PM2.5 particles, however, are smaller and having less momentum, remain entrained in the air-flow and pass to the filter, where they are collected.

The SSI cut-point is affected by airstream velocity / flow-rate, acceleration nozzle diameter, and particle density, composition and shape. The symmetrical design of the SSI overcomes the effect of wind direction and the inlet design makes the collection efficiency independent of wind speeds up to 36 kilometres per hour.