My grandma lives my parents and she's coming to that age where she starts forgetting things.
What mum is concerned about is grandma leaving the stove on while she's upstairs watching TV. There were times when she left a pot on the stove and evaporated all the water in it causing to burn the inside and leaving a smoky scent throughout the house. She cooks a lot as well.
Because I work throughout the day and so do my parents, there's no one at home to keep an eye on her.
Is there some sort of device that detects when there's a vast amount of gas in the house or even a fail safe device that turns off the stove?
For an audible alert, maybe something like this?
http://www.amazon.co.uk/Mains-Powered-Household-Gas-Detector…
http://www.ebay.com.au/itm/GAS-DETECTOR-IDEAL-FOR-CARAVANS-R…?
DISCLAIMER: I have NEVER used one of these products.
Best advice is to call a company that specialises in safety products.