a burner assembly and a gas box for an atomic absorption spectrometer are disclosed . the burner assembly has a spray chamber for receiving oxygen , fuel and sample material and a burner located on the spray chamber for receiving the mixture so the mixture can be ignited to produce a flame to facilitate analysis of the sample material by atomic absorption of radiation . pressure transducer is provided for measuring the pressure in the spray chamber so that the pressure is not of a predetermined level the burner can be shut off . a fuel line supplies fuel to the spray chamber and an airline supplies air to the chamber . the lines and include flow restrictors and creating an accurate pressure drop thereby ensuring correct mixture of air and fuel .