Ray - Cheers for the info link.
Tropicgirl - Hope this helps and does not confuse. (sometimes I make no sense!)
Boiling a pot of water may work to a degree, but keeping a humidity level up seems to be about combination of available water, keeping ventilation low (to help stop heat and water vapor escaping) and of course the surrounding heat.
However boiling water might be very inefficient way of keeping humidity up, when compared to say a humidifier.
Don't forget steam can scold humans let alone plants, if too close.
Also you don't want to make your house humid, the dampness may lead to rot and mold within the building structure. What I will be trying to do if required if confining the humidity to a certain spot (In the home). Outside I will be experiment with a kind of tent and camo set up and see if I notice any changes)
Ever woken up in a tent in the middle of an summer, talk about sauna!