These are made to fit on top of a camping cooker. I found that by taking off the pan stand, this would fit directly over the cooker burner in the campervan (and later my caravan, and on low is pretty powerful. Basically it's a heat shield and looks like two perforated tin cans put together one inside the other, and works very well. Same safety warnings apply, although basically this is a radiant heat shield for a cooker.
You need to use it a few times to 'wear it in' as it smells a bit until it's been used a few times. But far far safer that anything else non-electric.
Even this can be dangerous. All the instruction I have had (either written or verbal) with our 3 vans have stated that you should not use the cooker for heating.
However I realise that people do so if you do use a cooker for heating, or you use any other form of freestanding gas heating in a motorhome/campervan/tent or even your home please, please get and use a carbon monoxide detector.
Through no fault of my own I have had carbon monoxide poisoning and fortunately lived to tell the tale. It's not nice.
Amazing family weekend with old steam engines, classic car displays, market stalls, and full catering and bar. And camping on site - Save £25 by booking in advance.