Picture of How To Smell Pollutants
This Instructable explains how to use a gas sensor with your Arduino.

This lets your Arduino smell (and hence you program responses to) overall gas levels for a variety of nasties, including ethanol, methane, formaldehyde, and a bunch of other volatile organic compounds.

My cost to make this actual device was under $100, including the full Arduino kit. Here's a video:
And no, I won't put a shirt on:-)

I've got kits / finished versions of this and some other projectsfor sale @ my website

The closest comparable commercial products I can find are:
-a commercial-quality detector: $2500+
-a lab monitor: $295
-a one-off test kit for volatile organic compounds: $234

I learned about this after hearing about some guys who added VOC sensors to toy dogs. Not sure where/if the docs on that project are, but here's the guide that I followed.

Links explaining what VOCs are and why you might want to care:
-Some symptoms of overexposure to VOCs
-an OSHA regulation on formaldehyde levels
-information on sick building syndrome: 'A 1984 World Health Organization Committee report suggested that up to 30 percent of new and remodeled buildings worldwide may be the subject of excessive complaints related to indoor air quality (IAQ).'
-The Inside Story: A Guide to Indoor Air Quality: "For pollutants other than radon, measurements are most appropriate when there are either health symptoms or signs of poor ventilation and specific sources or pollutants have been identified as possible causes of indoor air quality problems. Testing for many pollutants can be expensive. Before monitoring your home for pollutants besides radon, consult your state or local health department or professionals who have experience in solving indoor air quality problems in non-industrial buildings."
yugnats2 months ago

Hi, great project! Could I use other sensors? I was thinking about using the TGS2602 rather than the TGS2620 as I'm trying to monitor air quality outside my garage. Thanks!

cooperwood6 months ago

I am using AutoRae calibration sensor to sense smell for my project and is working fine.

PatrickG58 months ago

Are you still mailing the kits for this?

Cyme4 years ago
VOC stands for volatile organic content. If your fart, the methane you smell is a VOC. If you drink a beer or a scotch--ethanol--the odour you smell are all VOCs. If you cook fries, the grease you smell is again a VOC. If you paint with an oil-based paint, the solvent from the drying paint are VOCs. And yes, these are air pollutants that can contribute to smog.

gasump Cyme9 months ago

VOC stands for Volatile Organic Compound. Methane is a colourless odourless gas. The rotten eggs type smell commonly attributed to Methane is actually Hydrogen Sulphide commonly generated alongside Methane in, for example, rotting vegetation in the anaerobic process. H2S is a dangerous gas that causes many deaths worldwide every year. This comment may seem 'picky' but if people are going to use projects like this for real/health monitoring you need to get the basic science right or you could end up endangering someone.

smohamad31 year ago
Is it possible for the experiment to work well if i changed to arduino uno and use 39k resistance? -urgent-
please help me.. ^^
jknotts11 year ago
Volatile Organic Compound not content and the equipment involved in Environmental and Occupational health surveillance is a bit more complucated because of the sensitivity that is required to detect many of the toxic industrial materials osha and the EPA regulate.. To coduct a survey you would at a minimum require the use of a photo ionization mechanism calibrated by a federally certified lab. and the sensors for things like oxides of nitrogen, or iso-cyonates exposure levels on a time weighted average basis and that is why you pay $3500 for a multirae gas detector that only reads O2 levels, and 3 slots for toxic gas sensors. I am also interested in designing equipment for health surveillance as well as creating custom microenvironments this design is definitely great for monitoring and control automation if you are interested in exchanging ideas on either subject I'm game. I am new to the electrical engineering field I am half way through my BAS in EE but my background includes 13 years of experience in the Army specializing in Environmental, occupational, and public health and years of college in an environmental science program before switching to a Major in Electrical Engineering.
alavasier2 years ago
I liseman. How did you convert the values readed by the microcontroller to ppm of pollutants? did you calibrate the gas sensor, if so how did you do it? or how did you find teh R0 of the sensor?
liseman (author)  alavasier2 years ago
hi alavasier,

You can roughly calibrate the sensor by matching readings to the datasheet, eg http://www.instructables.com/files/orig/FCF/712B/FEMHW1YS/FCF712BFEMHW1YS.pdf . Putting the sensor in 100% concentration of target gas vs. 100% of a non-detected gas will let you determine min and max.
ftreska liseman2 years ago
How did you set the sensor so its already have a value in ppm ( the value gas in actual condition) which read by microcontroller?
ozmel2 years ago
hi i am doing a wireless sensor network for hydrogen monitoring. i chose arduino uno and MQ-8 hydrogen sensor. i want you to help for the design. sorry for my english i am a frenchspeaker. thank you
bojanmanev4 years ago
can i buy arduino online please tell me the site for buy a want to do this but i haven't got a arduino i m from macedonia
You can buy them assorted places online, in prebuilt or kit form. Since they are from Italy, I expect they're just as easily available in Macedonia as here in the US.
The main site is www.arduino.cc , but there are assorted other sites that sell them.
colorex3 years ago
How To Smell Pollutants? Can't stop thinking bout this...
transuranic4 years ago
could iit be modified to smell any chemical?
Unfortunately, no.
skybosg4 years ago
Put a shirt on!
yeagerxp4 years ago
you should be able to buy arduino from WEB, search for it, it is available in EUROPE,
I know a better way. If you breathe something, and promptly drop dead, it's usually a sign of polluted air. So then you'll know in the future - oh wait.
Actually I've heard of this being done, with birds in cages, not people.
godscountry4 years ago
add this board and sensors,to a quad rotor,a low cost way to inspect accident sites,train wrecks,chemical spills etc. without the risk to humans or animals .Maybe a sniffer for explosives,drugs
tmort6 years ago
can this circuit be modified to add more sensors for mulitple gases and a datalogger?
liseman (author)  tmort6 years ago
hi tmort, yeah, that should be pretty easy to do. if you need accuracy in terms of actual gas concentrations, consider borrowing a fancy, professional gas sensor to calibrate your arduino-based one... hope this helps! -luke
Coffee bean6 years ago
nice! think it could recognize welding gas leaks?

This is For acetylene There's all sorts of Gas sensors though
polar bear67 years ago
why dont you have a shirt on lol
timmy1234s7 years ago
Here is a better place to get the sensors. http://www.futurlec.com/Gas_Sensors.shtml
Could u upload a vid of u fartin on it and the reaction on PC. lol would it go crazy or what :O LOL
I had the same idea.
Great Instructable! Wow! Well Done! I just voted even though votes don't count for this contest but this should win! Great work. I think I read that article your talking about in Make magazine. Nice instructable!!
LinuxH4x0r7 years ago
Woah! I just use a fan when in doubt! Great job!
Looks... complicated.