Last winter, I became curious as to what kind of humidity systems were
installed in rooms with hot air heat and what levels of humidity were
being maintained. So, I conducted a survey of a number of the major
collectors and restorers.
The two primary means of adding humidity in the winter are systems that
inject steam into the air flow and systems that blow air over a water
drenched wick. The predominant system appears to be the steam system.
Humidity levels in the winter are generally maintained at the 40-50%
level. This corresponds also to my personal experience with a steam
system in our new music room.