I have made many of these and at first I thought that they were a great idea.
After using one in anger, I am 'unimpressed' with them.
I have found them to be potentially dangerous, smelly and smokey.
Also to not give a lot of heat out.
Let me explain.
When the stove is lit, eventually the whole cardboard lights. after a while all the wax in the tin is molten. DO NOT TRY MOVING IT! or knock it.
An instant fireball of molten LIT wax is what you end up with.
Also if any water spills into it , it spits a lot and flares. So watch a cup boiling over.
Any wind takes the heat away, so I advise using it like an alcohol stove.
The ones I made gave off lots of soot. About as much as a wood fire. Far more then I have had with esbits.
The smell was not very good, It reminded me of a sooty fire.
I have twenty or so of these made up and I will keep them for 'last resort'. But there is no way I would ever use one inside as an emergency stove.
An alcohol stove. I have used inside same with others.
Depends upon what you expect out of the stove. But the thing that most surprised me (it shouldn't of) was the molten wax and hoe easy it was to get it to spill and cause a fire you don't want.
Perhaps I 'over filled' the tins with wax. I just poured in until the tin was full and the cardboard was covered.
Alan