[poll] CO2 Measurement Stuffy air alert

Carbon dioxide (CO2) is not just a threat to the environment, it is also an important and often ignored factor in determining air quality in the offi ce and at home. Too high a concentration of CO2 leads to feelings of tiredness, disturbs concentration, and causes headaches. The CO2 meter described here makes it easy to determine the concentration of carbon dioxide in the air. A microcontroller monitors the measured value and can trigger an alarm or start up a ventilation system when a preset threshold is exceeded.

http://www.elektor.in/projects/co2-measurement

Its a great project

we can also use MQ-7 Gas Sensor
application circuit http://wiring.org.co/learning/basics/airqualitymq135.html

Product Link
http://www.onlinetps.com/shop/index.php?main_page=product_info&cPath=76&products_id=988

thanks tps.does the sensor give a linear relation with the concentration. please reply it is urgent.