The CO2 Check™ device is equipped with an industry-leading Senseair CO2 sensor and uses nondispersive infrared technology (NDIR). The device constantly draws in air, measures the CO2 levels in the air, and updates the readings on the OLED display every 2 seconds. The device has a range up to 10,000 ppm. To accurately measure the CO2 levels in a room, the device should be placed at least 3 feet off the ground and at least 6 feet from windows or doors. Optimal placement is generally on a table, desk or wall in either the middle or perimeter of a room. We also recommend not positioning the device too closely to one's body or face as this will result in high readings as a result of the device measuring the user's own personal exhaled air and not the mixed air in the indoor environment.