A 7-inch (17.78 cm) by 9-inch (22.86 cm) black rubber gas mask. The C3 NBCW (Nuclear, Biological, and Chemical Warfare) protective mask is a full-face respirator, primarily used by military personnel and first responders. It was developed in Canada, with early versions potentially dating back to the 1950s and 1960s. The C3 is an upgrade to the earlier Canadian Light Respirator series and was in service until the 1980’s.