Abstract: A method of purifying bleed air from an engine heats the bleed air only to an extent necessary for the bleed air to react under catalysis from a noble-metal-based reactor bed, converting the contaminants to filterable form. The contaminants are then removed with a post-treatment filter. A purifier functioning according to the present invention, which heats the bleed air to a temperature no greater than 450° F. which it attains without a combustor, thus releases less heat to adjoining components than a prior-art purifier, and outputs purified air at a lower temperature than does a prior-art purifier, which typically needs to include a combustor. The purified air is sufficiently cool as to be suitable for immediate release into interior compartments occupied by humans or the air conditioning system.