Pray so they do not serve alone. Ephesians 6:10-20
Chemical weapons effects dissipate over time. Most likely it would be something else, I think.
This is true of non-persistent chemical warfare agents.
There are also persistent chemical warfare agents, which hang around for a long time.
They have different tactical and strategic uses. Examples; persistent agents can be used for long-term area denial, whereas non-persistent can be used for short-term area denial. Either can also be used to kill and incapacitate the enemy, and degrade enemy performance due to hampering effects of protective gear. Various individual agents and classes of chemical agents have various uses and advantages.