Mpod code is the firmware running on the dedicated environmental sensing platform--Mpod, which is a air pollutant sensing device designed by researchers -- --in University of Michigan. It controls the sensor data collecting, data transmission, and all the other on-board components. This firmware is compiled and tested under the Arduino environment V0022 (http://arduino.cc/en/main/software). It can be uploaded to the Mpod board via bluetooth directly is a bootloader is pre-installed. Otherwise, it can also be uploaded using an Atmega AVR programmer via the 6-pin programming header on board. The functions of the firmware can be described in three categories: data collecting; data transmission; and other functionality. This firmware also has many features designed to enhance the in-field reliability, such as CRC data checking and watchdog timer.