I have used a butane stove in the kitchen here during neighborhood/area blackouts with no ill effects. I normally have a window partially open, so my CO detector has not been concerned.

I have a stainless steel Gas ONE model that boils water faster than the electric stove top, good single burner stove — no issues. At least a couple Iwatani models seem to be professional grade. These butane stoves have similar designs; imo it’s about build quality and burner output.

I prefer the full size version of these stoves. The mini’s have an issue with hot pans extending over the fuel canister compartment which is not a good thing.