Binary chemical weapon

Binary chemical weapons or munitions are chemical weapons wherein the toxic agent in its active state is not contained within the weapon. Rather, the toxin is in the form of two chemical , physically separated within the weapon. The precursors are designed to be significantly less toxic than the agent they make when mixed, and this allows the weapon to be transported and stored more safely than otherwise. The safety provided by binary chemical weapons is especially important for people who live near ammunition dumps.

The chemical reaction takes place when the weapon is deployed. Firing the munition or other deployment action removes the barrier between the two precursors, so they can react with one another. Commonly, there is a final stage which utilizes a bursting charge to aerosolize and distribute the chemical agent.

Binary chemical weapons are chemical weapons within the scope of the Chemical Weapons Convention and therefore their production, use and stockpiling is forbidden in most countries, as at least one of the individual chemicals is likely to be a Schedule 1 chemical for which large scale production is forbidden.

One example of a binary chemical weapon is the United States Army M687. In the M687, methylphosphonyl difluoride (military name: DF, a Schedule 1 chemical) and a mixture of 2 agents held in chambers within the weapon, separated by a partition. When the weapon is fired, acceleration causes the partition to break, and the precursors are mixed by the rotation of the weapon in flight, producing sarin nerve gas.

The Soviet Union and later Russian Federation experimented with binary weapons capable of mixing and distributing two agents that would work together in worsening the effects of the weapon, an example of which would be the combination of nerve agents with blister agents.

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