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 Ranges 14 to 140°F (-10 to 60°C)
Accuracy ±0.9°F (±0.6°C)
Resolution 0.1°F/°C
Measuring Range 0 to 99.9% RH
Accuracy ±3% (10 to 90% RH) 
±5% (<10% & >90% RH)
Resolution 0.1% RH
CO2 (Carbon Dioxide)
Measuring Range 0 to 5,000 ppm
Accuracy < 999 ppm: ±40 ppm
>1,000 ppm: ±5% Rdg 
Resolution 1 ppm
General Specifications
Response Time 1 sec
Display Triple LCD display
Backlit Display Yes
Dew Point / Wet Bulb Calculation Yes
Data Hold Yes
Min, Max and Avg Functions Yes
CO2 Short Term Exposure Limit (STEL) Yes (15 mins)
CO2 Time Weighted Average (TWA) Yes (8 hours)
Alarm Yes (audible)
Auto Shut-off Yes (after 20 mins/off)
Low Battery Indicator Yes
Power Supply 4 AA Batteries
Battery Life Approx. 24 hours (continuous use)
Product Certifications CE
Operating Temperature 14 to 122°F (-10 to 50°C)
Storage Temperature 14 to 140°F (-10 to 60°C)
Operating Humidity Range 10 to 85%
Dimensions 7.9 x 2.7 x 2.3" (200 x 70 x 57 mm)
Weight 6.7 oz (190g)