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."
Step 1: Gather Your Supplies
-an Arduino (or equivalent)
-a cable to hook the Arduino up to your computer / provide power
-a computer to read values
-a potentiometer or resistor of known value. anywhere from 500-1k ohms should work
-the gas sensor: a pain to buy in small quantities. i bought 2 and they cost like $22 each, but volume orders get way cheaper... the specific sensor i used was figaro sensors's 2620.
Here's what I used:
-the arduino kit I used
-the different sensors available from Figaro (use different sensors to 'smell' different things)
It' useful but not necessary to have a multimeter and wire stripper handy...
The pdf included with this step is the price list from the sensor manufacturer as of March 2008.