[greyfoxx39]

Correct. Rural areas that don't have natural gas pipelines available have big tanks of propane next to the house for water heater, furnace and gas range in my part of the country.

[Cboldt]

Water heater and furnace vent the flue gas. Range top doesn't, but is usually close to a kitchen vent anyway, and for cooking, the mass of gas burned v. the volume of a kitchen poses no risk of CO poisoning.