From 2/2, gas alarms are mains but if the same as last year then the power supply is about 12v and it runs ok from boats 12v system, also have fire blankets.
I'll add the gas alarm to my Aldi bilge alarm (sold for bathtubs) and the Lidl smoke alarm & CO indicators! Brilliant cheap safety stuff, why can't other big chains supply that sort of safety stuff at a similar price?