nitrous safty purge

anyone here have a safty purge for thier nitrous bottle. IM not talking about the line purge that bleeds the system and emits a huge cloud of nitrous. Im talking about a line that comes from the bottle valve that leads outside the car so incase the bottle has a leak the n20 doesnt fill the car with gas but leaks outside into the atmosphere. Im asking this because my NOS brand bottle did not come with one and want to know what other people did about this.
ANy input would be appreciated.

found the answer to my question long ago.

What i was talking about is a blowdown tube. They are mandatory for nrha tracks and are a good safty item to have. The retail for like 25 bucks.