Safety Pressure Release Valve on torches

[tomexposure]

Hi there,
I was just wondering if anyone could let me know the relevance of the pressure release valves on some of the torches. For example the Bersub and the FaMi lights have them but then there are other expensive lights which do not have them. Could it be a potentially leaky area or it there because of the potentially of leaking.
Hopefully someone can elaborate on my queries and let me know if you think it is really necessary.

Thanks a lot,
Tom