The Extech CO250 air quality meter measures carbon dioxide (CO2), temperature, humidity, dew point, and wet bulb. It also features data logging capabilities and calculates statistical weighted averages of TWA (8 hour time weighted average) and STEL (15 minute short term exposure limit). The CO250 checks CO2 concentrations using a maintenance-free NDIR (non-dispersive infrared) CO2 sensor.

Measurement ranges: CO2 0-5000ppm, temperature 14-140°F (-10 to 60°C), humidity 0.0-99.9% RH. Resolutions: 1ppm, 0.1°F/°C, 0.1% RH. Other features: user programmable audible alarm, backlit triple LCD display, built-in RS232 interface for capturing readings onto a PC, data acquisition software and cable included to record and document CO2, humidity, and temperature data.