This paper is supplementary to one which appeared in the December, 1942 issue of this journal. In many applications of bactericidal lamps in air conditioning—such as food preservation, processing, etc.—low concentrations of ozone are desirable to protect surfaces and air pockets not reached by the radiation. A few tenths of one part of ozone per million parts of air is generally sufficient and is obtainable by selecting a lamp with a wall which transmits in addition to the very bactericidal 2537A radiation a few percent of 1850A. The latter is absorbed by the oxygen in the air forming ozone. The reciprocity law (amount of bactericidal action proportional to concentration×duration of ozone) is applicable for moderate concentration ranges. The bactericidal effect of ozone is nearly independent of humidity for surface infection of foods, etc., while high humidity is required for destruction of air borne bacteria. No oxides of nitrogen are produced by high transmission glass or quartz lamps. The ozone output of a lamp is reduced by decomposition by intense 2537 radiation either from the same lamp or from another lamp nearby. Moderate increases in the temperature of a high transmission lamp does not affect the ozone output but increases the dissociation constant until, at 150°F, practically all the ozone is immediately decomposed. The ozone concentration produced by a lamp is substantially reduced by rise in relative humidity, which moderately absorbs 1850 radiation and decomposes much of the ozone produced. Approximate reflection coefficients for 1850 radiation at various surfaces have been obtained by an indirect method.

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