“A competent chemist could make it, and possibly very quickly, in a matter of days,” says John Gilbert, a senior science fellow at the Center for Arms Control and Non-Proliferation, who spent much of his Air Force career assessing countries’ WMD capabilities. Producing sarin doesn’t require any kind of massive facility; a roughly 200 square foot room would do.
Attackers also don’t require much of it to do serious damage. Gilbert estimates that the Khan Sheikun devastation came from roughly 20 liters of sarin. (Remember: At one point Syria had stockpiled nearly 1,300 tons.)
“It would be possible to obtain, retain, or make relatively small amounts of sarin that would be hard to detect, if somebody really didn’t want them detected by an international organization,” says Gilbert.