Gas detector.

The description says: "12V model with non-polarised (reversible) power terminals for easy wiring ". It also says it has a "relay output". II should guess the red and black for power leads and the other three connect to single pole double throw relay. You might need to connect it to a power supply and expose it to gas to be sure which two represent the n/o contact. Or you could just join the two which are currently shorted together and use with the one that isn't for a normally open switch if you need one.

Thanks for the help I had guessed what the red and black were but the others confused me, Sounds like I couldn't do it much harm

I often used to wonder about the gas man going up and down the street with a naked flame looking for a colour change that indicated a gas leak.I mean we all could smell it, but it seems it can go a long way underground till it finds its way out. I realise its quite safe while trying to find the source, but it frightened the heck out of me the first time I saw it done. Has to be in open air of course or boom. Brian