An MC 331 cargo tank is used exclusively in chlorine service. Under 49 CFR 180.407, what leakage test interval applies to this tank?

49 CFR 180.407(c)

Chlorine is an extremely hazardous, highly regulated lading, yet DOT allows a longer leakage test interval for qualifying MC 330/331 tanks in dedicated chlorine service because of the robust construction standards those tanks already meet. Understanding this exception keeps a driver from mistakenly treating a compliant chlorine tanker as overdue.