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
PORTABLE O2/CO2 ANALYZER - Geneq Online
Air / CO2 Gas Mass Flow Meter (plus Kit) 5300-3 | TSI
RI-600 Standalone Carbon Dioxide (CO2) Gas Monitor by RKI Instruments
Coreel 4 Gas Monitor, Portable CO2, H2S, O2,EX Gas Detector Meter - Ready to Use (Orange) - - Amazon.com