The Arduino makes an ideal platform for prototyping and data collection with the SenseAir K series of CO2 sensors.
Arduino CO2 Sensor Application Note
From Wikipedia:
Arduino is a single-board micro controller to make using electronics in multidisciplinary projects more accessible. The hardware consists of an open-source hardware board designed around an 8-bit Atmel AVR microcontroller, or a 32-bit Atmel ARM.
The software consists of a standard programming language compiler and a boot loader that executes on the micro controller. Arduino boards can be purchased pre-assembled or as do-it-yourself kits. Hardware design information is available for those who would like to assemble an Arduino by hand.
When using the Arduino software stack, all boards are programmed over an RS-232 serial connection, but the way this is implemented varies by hardware version. Serial Arduino boards contain a level shifter circuit to convert between RS-232-level and TTL-level signals. Current Arduino boards are programmed via USB, implemented using USB-to-serial adapter chips such as the FTDI FT232. Source