Recently, red phosphorus is widely used in military applications as the base material in screening smoke munitions. In this study, in order to clarify the IR - screening properties, the IR transmission spectrum of red phosphorous smoke was measured in our laboratory. As the result, it was found that far - and middle IR screening factor was absorption of phosphoric acid. It was also found that IR - screening performance was not dependent on the combination of oxidizer and metal, but dependent on the amount of red phosphorus.