Flue gas loss is the calculated percentage of energy that escapes unused during combustion. This is calculated using measurement data via a defined formula. In principle, according to this formula, low flue gas temperatures or a high CO2 concentration, for example, have a positive effect on flue gas loss. According to the 1st BImSchV, the following limit values must be observed: ≥4 – 25 kW = max. 11%, > 25 – 50 kW = max. 10%, > 50 kW = max. 9%. The lower the flue gas loss of a heating system, the higher its efficiency (100% ./. 5% flue gas loss = 95% efficiency). The calculation of flue gas loss marked the beginning of the ecom flue gas analyzer success story in 1985.