I found the manufacturer of Sparkfun's gas sensors:
http://www.hwsensor.com/english/product ... ductor.htm
http://hanwei.manufacturer.globalsource ... nsor/2.htm
http://www.alibaba.com/member/rhj2000.html
Complete product line:
MQ131: O3 (ozone) detection in air quality control equipment within 10ppb to 2ppm
MQ132: C2H2 (acetylene) detection, in air quality control equipment within 500 to 2,000ppm
MQ133: for CO2 (carbon dioxide) detection, in air quality control equipment within 500 to 2,000ppm
MQ135: for NH3, nox, alcohol, benzene, smoke, CO2 and other gas detection in air quality control equipment
MQ136: H2S detection in air quality control equipment within 1 to 100ppm
MQ137: NH3 detection in air quality control equipment within 5 to 200ppm
MQ138: n-hexane, benzene, NH3, alcohol, smoke, CO and other gas detection in air quality control equipment for buildings/offices
MQ139: freon in refrigeration and air-conditioners spot detection application within 500 to 10,000ppm freon
MG811 solid electrolyte cell sensor for CO2 detection range 350 to 10,000ppm
I'd be very interested in seeing CO2 (MG811) and O3 (MQ131) levels. If we can get other people to build identical balloons and launch them around the world we'd be able to look at the ozone layer and carbon dioxide levels in the atmosphere in different locations which would be very interesting.