M2 gas mask
... that the M2 gas mask protected the wearer for at least five hours against the common World War I chemical weapon phosgene?
... that the <b id="mwFXw"><a href="./M2_gas_mask" id="mwFX0" rel="mw:WikiLink" title="M2 gas mask">M2 gas mask</a></b> protected the wearer for at least five hours against the common World War<span id="mwFX4" typeof="mw:Entity"> </span>I chemical weapon <a href="./Phosgene" id="mwFX8" rel="mw:WikiLink" title="Phosgene">phosgene</a>?