FWIW, if you own your home, have the $$ and plan on staying a while, it is well worth it to have a humidifier installed in your central heating unit.
We have one in our house and it is wonderful. The midwest winters are cold and the gas furnace will really dry out things. I think it was less than $500 installed and basically just fits in the central air duct for the HVAC system.
The one we have humidifies the whole house and hooks up to a tap water line so you never have to worry over it emptying. There is a filter-like grid thing that requires changing once every six months or so, but other than that it is pretty much hastle free.
I have to crank it wide open to hit 40-45 in the dead of winter, but it will keep it there.
BTW, in addition to safety for your bass, you get a much more comfortable environment to live in the winter. Your skin, eyes, nose, throat and lungs will thank you. If you have little ones, you hear a lot less hacking and scratchiness.
If you sing (or in my case attempt to) you'll really appreciate it.
Chas