the instant heater works on LPG, butane or propane, there is no electricity required, the "piezzo" lighting works with two 1,5 Volts batteries.
This almost is what I have in mine:
https://www.befr.ebay.be/itm/8L-2-1-...U1X~:rk:4:pf:0
As said, I put it into a box with outside ventilation, it doesn't burn fresh air from inside the living space, and the exhaust gases go outside either.
Watch out, some of those heaters works only on "natural" gas, not on butane/propane...