LP shutoff solenoid valve

[Midwilshire]

We're looking to put in an electric valve to turn on the LP at the tanks when needed, and turn them off immediately thereafter.  I was going to buy a 24vdc one to match the house system, but now I'm thinking I might as well interconnect that solenoid valve with the fire alarms for automatic shutoff, just in case we forget to turn the tanks off.

Could someone describe how they interconnected theirs?  What voltage is the signal wire on a typical fire alarm?  Do you use that signal to open a normally closed relay in the solenoid control circuit?

Thanks very much,

Mike