49 C.F.R. § 176.220
Smoking or open flame and posting of warning signs
(a) Smoking or the use of open flame is prohibited in any hold or compartment containing a Division 2.1 (flammable gas) material, near any Division 2.1 (flammable gas) material stowed on deck, or near any ventilator leading to a hold containing this material.
(b) A sign carrying the legend: