State Fire Marshal Stephen Coan says it's important to check propane grills for leaks as summer approaches, but there's no sign of a widespread problem after recent reports of tampering.
Coan investigated after Cape Cod fire departments got calls this month about suspicious blue color on brass propane tank valves. The discoloration was feared to ammonia contamination and an explosion risk. He said Friday only one 20-pound gas cylinder among more than 50 tested had been filled with ammonia, which could weaken the tank.
Methamphetamine makers have put ammonia in empty propane tanks, but Coan said that's no longer common.
He said brass exposed to ammonia is light blue, while normal corrosion is blue-green.
Coan said people don't need to be concerned about ammonia if they don't smell it, and have kept their tanks secure.