BTU-4500 Features include the following:

• Up to Four Gas Sensors:
  O₂, CO, NO, & NO₂
  OR O₂, CO, NO, & SO₂
  OR O₂, CO, NO, & C_xH_y (HydroCarbons)
• Dilution Pump For CO Auto-Range Measurements Up To 50,000 ppm
• Built-In Impact Printer (non-thermal)
• Low NO_x Capable with 0.1ppm resolution
• ALL Gas Sensors are Pre-Calibrated & Field Replaceable
• Efficiency, Excess Air, & CO₂ Calculations
• Stack Gas & Air Temperature Measurements
• Draft & Differential Pressure Measurements
• External Water Trap for Condensate Removal
• Rechargeable Lithium Ion Battery Pack
• Unbreakable Metal Hose Connectors
• Internal Memory (up to 900 tests)
• PC Software Package
• Field Upgradeable Kits to add more sensors!