The chemical reaction takes place while the weapon is in flight. Firing the munition ruptures the capsules. The munition spins rapidly in flight, which thoroughly mixes the two precursors, so they can react with one another. Finally, a bursting charge aerosolizes and distributes the chemical agent.
One example of a binary chemical weapon is the United States Army M687. In the M687, methylphosphonyl difluoride (known to the military as DF) and a mixture of isopropyl alcohol and isopropyl amine (known as OPA) are 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.
Unconfirmed sources have stated that the Soviet Union was experimenting 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.