Other Constituents
Hydrogen peroxide is a very active oxidizing agent. Rain water and snow contain very small traces of it. Hydrogen peroxide is not constant in air, but may be found in very small quantities.
Air also contains small traces of helium, krypton, neon, xenon, which have no important bearing from a hygienic standpoint. Nitric, sulphuric and other acids will at times be found in the atmosphere. These acids are formed principally from industrial processes and will, therefore, be found near industrial centers, rather than in the open country or at sea.