A residential combustion analyzer is a handheld diagnostic instrument used to measure the gases and conditions produced by fuel-burning appliances like furnaces, boilers, and water heaters. By sampling the flue gas, it evaluates key parameters such as carbon monoxide (CO), oxygen (O2), carbon dioxide (CO2), stack temperature, and draft pressure. These measurements allow technicians to assess combustion efficiency, identify unsafe operating conditions, and properly tune the appliance for optimal performance and fuel use. In short, a combustion analyzer ensures heating equipment is operating safely, efficiently, and in compliance with industry standards.