The gas-fired heating unit has an atmospheric gas burner including a mixing chamber and a burner medium covering the mixing chamber, a combustion chamber in which the atmospheric gas burner is arranged, a fuel gas/air supply system that has respective inlets for fuel gas and combustion air and an ignition device having at least one pilot flame and supply pipe for pilot flame gas associated the mixing chamber. In order to reduce NOx emissions and reduce ignition noise, the ignition device has an upwardly open mixing space arranged in the mixing chamber and immediately under the burner medium, the supply pipe for the pilot flame gas is connected to the mixing space and the mixing space is provided with an inlet for primary air.