The Dwyer AQH-20 Indoor Air Quality Meter reduces the number of instruments a contractor has to carry by measuring carbon dioxide concentration, air temperature, and humidity percentage in one device. A large backlit LCD display shows all three parameters simultaneously. The Model AQH-20 can display dew point or wet bulb temperatures in place of the ambient temperature.

Minimum, maximum, and average readings are easily accessible through function buttons. Pressing the hold key holds current values for recording. An audible alarm warns when ambient conditions become hazardous. Specifications: CO2 0-2000ppm (±30 ppm ±5% of reading); temperature 14-140°F (-10 to 60°C) ±0.9°F (±0.6°C); humidity 0-99.9% RH (±3% RH 10-90%, ±5% elsewhere). Response times: CO2 <30 sec, temperature <2 min, humidity <10 min. Uses (4) AA batteries, 30 sec warm-up.