I grow my orchids indoors in NE USA. I've been looking at back-up heat
sources for my orchid room for this winter, just in case the power grid
goes down again.

After doing some on-line research, I have concluded that Kerosene burns
dirty and gives off ethylene gas, which is supposedly not good for
orchids and causes bud blast, at the very least. By contrast, Propane
gas burns clean, but the tank must be kept outside because if the tank
leaks, it's very dangerous--Propane gas settles in the lowest point in
a house (like the furnace room in the basement) and is highly
explosive.

There is another product called a snap-on stove, which is really a
small assembly that looks like couple of soup cans that screw
together. The top bottom part burns gelled ethanol fuel. It produces
2,500 BTUs of heat per hour, and will maintain a room at about 60
degrees for 4 hours. The manufacturer says it's safe to use indoors. It
is cheap. Does anyone know if this product gives off fumes, such as
ethylene fumes, in an amount that would be harmful to orchids? Thanks
for any feedback.