Holding the Breath
The first regulations and those in general use up to near the close of hostilities, prescribed that the soldier should hold his breath and adjust his mask. It seemed impossible to overcome the natural inference that “holding the breath” meant first the drawing of a full breath. This was obviously highly dangerous if gas were actually present before the alarm was heard, as was often the case with projector and artillery gas shell attacks. The change was then made to the phrase “Stop Breathing and Stay Stopped until the Mask is Carefully and Accurately Adjusted.”