Be careful. Even in Florida, I've seen more than a couple house fires from people using candles as heat. Kids or pets and candles don't mix well.
Propane is relatively safe, especially the catalytic units, and various models of heaters span a huge range of BTU and capacity. A popular one is from
Mr. Heater , which has an oxygen sensor.
Coleman has a variety of units, too.
Many use small disposable propane bottles, but can accept a converter for larger gas-grill-size tanks.
Ditto on the CO sensor... battery-powered and AC-with-battery-backup units are available.
Steve