Tear Gas rounds for Short Range Missile launchers were created by the Terran Hegemony in the mid-2370's. Developed as a less lethal alternative to standard SRM loads, the Tear Gas rounds are not usually used by military forces. The most common users are law enforcement agencies who need to disperse a large group of people. They're launched either from an infantry-style launcher or can be loaded into the magazines of PoliceMechs like the Copper or PM6 Peacemaker.
Because they are an area effect weapon, Tear Gas rounds are not targeted at a unit like standard SRMs. They are instead fired near a target, and the irritant payload then spreads out over a wide area. Due to this unique targeting method, the Tear Gas SRM cannot be used with Streak, Narc, or Artemis fire control systems. They can be fired from standard SRM or MML launchers.
Since they're completely ineffective against most battlefield units, they are only rarely seen on the battlefield.
- Tactical Operations, p. 372, "Tear Gas"