Dwyer GSTA and GSTC gas transmitters monitor CO (gasoline engines) and NO₂ (diesel engines) in parking garages and loading docks. Field replaceable electrochemical sensors with 4-year typical life and 5,000-7,500 sq ft coverage.

GSTA models: field selectable analog outputs with invertible output via dip switch. CO ranges configurable from 0-50 to 0-500 ppm; NO₂ standard 0-10 ppm. GSTC models: BACnet or Modbus over RS-485 for building management controller integration. A-449 remote LCD display (sold separately) enables field calibration. CO accuracy: 2% full-scale; NO₂ accuracy: 3% full-scale. End-of-life indication when sensor replacement needed.