RV Furnace Misunderstanding

In a recent RVtravel newsletter a lady states: "I am new to owning and living in an RV so I am not familiar with propane heat. I have read that propane heat also puts out moisture." I believe it may have been prudent to tell her that the propane furnace, being a closed system to the outside air, will have no affect on moisture within the RV.  (No name) 

Actually No name, fresh air is drawn from outside the RV into three of the four propane appliances to mix with the incoming fuel, including the forced air furnace. Yes, it has a sealed combustion chamber, but moisture can still be generated inside the fire box through that fresh air intake. I’ve replaced many RV furnace combustion chambers that have rusted through. All propane flames/burners require a mixture of air and gas in order to support combustion and all will create moisture. The primary air volume is drawn in from outside the coach. That’s why it’s important to have the furnace inspected each camping season. If a rusty hole is created, carbon monoxide (CO) can escape into the living areas of the RV.