zxcvbob writes:

I buy E85 (gasoline and ethanol blend that's mostly ethanol) and use it as
lighter fluid to get the fire going. It burns *much* cleaner than kerosene
or other petroleum fuel, and it doesn't flash nearly as bad as gasoline.
Even this is often not enough and I have to open a basement window just
until I get the updraft going.

I've also read several times about techniques for building fast-burning
torches from newspaper to get the draft started. Those probably work
well in a fireplace, where the fire is right under the flue. But this
is a permanently-installed natural gas heater, with a metal flue duct
attached at an inaccessible place behind the heater (inside the original
fireplace space). There's no easy way to get something burning back in
there, right at the entrance to the duct, downstream of the draft
diverter.

Dave