Pollution consists of multiple substances, gases, ash, smoke, suspended dust, pollen, and volatile organic compounds. The latter, along with microparticles PM, are harmful to health, as they are so small that they penetrate our bloodstream when we inhale them. PUROH eliminates volatile organic compounds and microparticles in a very rapid four-phase reaction that results in harmless substances such as oxygen, water, and soluble carbonates. The air-free factor or natural detergent reaction occurs naturally in the upper layers of the atmosphere. PUROH generates the same higienizing effect as open air.