Amazon.com: Digital CO2 Meter with 9999ppm Measurement, Temperature, and Humidity Display | Indoor Air Quality Monitor : Industrial & Scientific
Industrial Air Quality Meter with Real-Time Data Recording of CO2, CO, O2, Temperature & Humidity,(6 in 1) by Lutron AQ-9901SD(Handheld Indoor Detector Sensor Meter Monitor Device Measurement): Amazon.com: Industrial & Scientific
Coreel 4 Gas Monitor, Portable CO2, H2S, O2,EX Gas Detector Meter - Ready to Use (Orange) - - Amazon.com