REED R9900 Indoor Air Quality CO2 Meter


This IAQ (indoor air quality) meter simultaneously monitors carbon dioxide, relative humidity, and temperature. The R9900 is capable of automatically calculating wet bulb and dew point temperatures as well as statistical TWA and STEL averages.


  • Triple LCD display simultaneously monitors carbon dioxide (CO2), relative humidity and temperature
  • Automatically calculates dew point and wet bulb
  • Calculates statistical weighted averages of TWA (8 hour time weighted average) and STEL (15 minute short term exposure limit)
  • User adjustable audible alarm
  • Data hold, Max/Min and average functions
  • Low battery indicator and auto shut off


Measuring Ranges14 to 140°F (-10 to 60°C)
Accuracy±0.9°F (±0.6°C)
Measuring Range0 to 99.9% RH
Accuracy±3% (10 to 90% RH) 
±5% (<10% & >90% RH)
Resolution0.1% RH
CO2 (Carbon Dioxide)
Measuring Range0 to 5,000 ppm
Accuracy< 999 ppm: ±40 ppm
>1,000 ppm: ±5% Rdg 
Resolution1 ppm
General Specifications
Response Time1 sec
DisplayTriple LCD display
Backlit DisplayYes
Dew Point / Wet Bulb CalculationYes
Data HoldYes
Min, Max and Avg FunctionsYes
CO2 Short Term Exposure Limit (STEL)Yes (15 mins)
CO2 Time Weighted Average (TWA)Yes (8 hours)
AlarmYes (audible)
Auto Shut-offYes (after 20 mins/off)
Low Battery IndicatorYes
Power Supply4 AA Batteries
Battery LifeApprox. 24 hours (continuous use)
Product CertificationsCE
Operating Temperature14 to 122°F (-10 to 50°C)
Storage Temperature14 to 140°F (-10 to 60°C)
Operating Humidity Range10 to 85%
Dimensions7.9 x 2.7 x 2.3" (200 x 70 x 57 mm)
Weight6.7 oz (190g)