This European Standard specifies the safety, construction and performance requirements for combustion product sensing devices intended to be used in combustion control systems, hereinafter referred to as CPSD. This European Standard applies to sensing devices for the measurement of combustion products from burners and appliances for domestic, commercial and industrial use burning:- gaseous fuels according to EN 437; or; - liquid fuels having a viscosity at the burner inlet of 1,6 mm2/s (cSt) up to 6 mm2/s (cSt) at 20 °C, higher boiling petroleum based first raffinates (viscosity greater than 6 mm2/s), that require preheating for proper atomisation. This European Standard applies to all types of stationary sensing devices measuring flue gas components O2, CO, CO2, H2, CxHy, NOx, SO2 or for a combination of them (multiple gasses). This European Standard applies also to sensing devices for extractive systems. This European Standard does not cover sensor requirements for combustible gas, combustible gas mixture and oil quality.