VENT FREE GAS LOG HEATER

67Dart273 said
In some areas unvented (vent free) appliances are not allowed. Do NOT use them in confined areas or sleeping quarters. For me, LP (propane) is much more annoying in that condition than is NG. Makes lots of humidity!!

It's actually the other way around. Natural Gas makes about 25% more water from combustion than Propane as a result of the chemistry of combustion.

Propane
100,000 BTUH = 0.98 Gallons of Water

Natural Gas
100,000 BTUH = 1.25 Gallons of Water