I haven't seen a gas oven that can work without electricity. A gas stove, yes, you can simply turn on the gas and quickly use a kitchen lighter to ignite the gas manually and hope not too much poisonous gas escaped the stove. But ovens? How?

Older gas ovens used a standing pilot light. They would work without electrical power. Really old ones you light with a match.

My kitchen has a gas range, the oven uses electical resistance/incandescent ignitors so it won't work without electrical power. The top burners have spark ignitors but of course I can light them with a match.

Many gas ovens (and stovetops) work just fine without electricity thanks to pilot lights.

The gas oven in my apartment has a pilot light that is always on, no electricity needed.

It's not poisonous.