Rheem TRD

[Twowaxhack]

For those who are interested this is a Rheem thermal release device that allows combustion air to enter the heater.

If the burn chamber overheats for any reason the oil filled vile will break and a spring activated door will close to stop combustion.

Here is a pic.

 

[Twowaxhack]

This will stop and extended vapor burn of flammable vapor by the water heater.

An example would be spilled gasoline in the area. The water heater would burn this vapor until the burn chamber overheated.