After two years of effort, the Department of Defense is field testing its new, M-50 gas mask. By late next year, production will begin. The 1.5 pound M-50 will replace three different gas masks used by the army, navy and air force. The M-50 is lighter than the masks it is replacing, more comfortable to wear and provides better protection. 

Although gas masks are rarely used, except for protection against tear gas in riot control situations, there has been a series of new ones developed since the five pound M2 gas masks of World War II. Several new masks were developed during the war, and culmination of those efforts was seen with the M9, which was introduced in 1947. There followed the M17 (which allowed you to drink) in 1959, and the M27 (which was a lightweight one just for protection from tear gas) in 1968. After that, the M30 ran into cost overruns in development and was dropped in the 1980s (but the navy and air force finished development and adopted it as the MCU-2/P). So the army came out with an improved M17A2, that made it easier to talk with the mask on. The M40 then came out in 1992. Actually, the M40 was basically an improved M30, which was sneaked past the media and Congress as the "new" M40. 

In 1996 the M46 (for aircraft crews) came out. In the late 1990s, it was proposed to develop one new model, the M50, for all services. This was also called the Joint-Service General-Purpose Mask (JSGPM) program. This model will build on all the earlier ones. Although millions of gas masks have been made for American troops in the last sixty years, none have ever encountered any enemy chemical weapons (a few have been sued when there were accidents with American chemical weapons.)