Abstract: An apparatus to detect and measure the amount of phosphorus in phosphorus-containing compounds comprises a burning chamber with a housing having an integral combustion chamber. A flammable reducing agent such as hydrogen is introduced into the combustion chamber along with a sample containing phosphorus admixed with air or oxygen. At least a portion of any phosphorus in the sample will be converted into phosphorus monoxide (PO) by the combustion. The resulting phosphorus monoxide is immediately drawn into a low-pressure, ambient temperature reaction chamber and reacted with ozone to convert the phosphorus monoxide to chemiluminescent phosphorus dioxide. A light-measuring device then measures the intensity of the light released from the chemiluminescent phosphorus dioxide.