Systems and methods using the properties of supercritical water to allow raw air including a contaminant to be combined with water and to be purified in a supercritical water oxidation (SCWO) process. A supercritical water oxidation (SCWO) air purifier will generally take in a mixture of water and raw air which includes oxygen via a pumping and mixing apparatus, put the mixture into a supercritical water reactor (SCWR), and run the resultant effluent stream through a system for separating the water from the resultant clean air and the other relatively harmless outputs of the supercritical water reactor (SCWO).