My chamber is a 50cm long piece of 2" galvanized steel pipe, this is sanitary pipe and (unfortunately) not for gas. And my PSV valve has no pressure rating written on it but it looks very heavy duty, but since I'll still have to hold this thing close to my face I'd at least like some kind of guideline on how much pressure she can handle

Currently i'm thinking around 25 bar will be safe, but if the valve can handle over 100 bar i might replace the sanitary pipe chamber with the same length of gas pipe (thicker walls) and aim for 55 bar (+-800psi)
Cheers