Hi Handbasket,
Yes, they do, which makes the Platinum Cat even more attractive as the water vapor goes up the chimney.
To avoid condensation the surfaces must stay above the dew point. Venting does help--particularly if the air stream coming in is warmed.
I would never use a blue flame heater while sleeping, nor any other non vented combustion heater.
Handbasket wrote:
Question for those who actually know... Does a catalytic heater put off water vapor like a Mr. Buddy heater? None? Less? The same? More? I really like my small Buddy heater, but the condensation on a cold night can be troublesome, even with adequate combustion venting.
Jim, "Manure occureth."