LED Digital Display High Sensitivity Wall Mounted Natural Gas Leak Detector Sensor with Battery back up 838-12

I just received 2 of these units and they did not come with instructions printed in EnglishI put 9 volt batteries in both of them and plugged them in but after a while they started malfunctioning and the batteries were extremely hotI had to take out the batteries and unplug them because I thought they were going to catch fire.It could be that they take 9 V rechargeable batteries but I cant find any info online about the product nor can I read the instructions.There is not a model number or U/L marking anywhere on the unit.I don't know if or how I can return them but this product is junk. I don't know how amazon can sell this in the US