Bemis Whole House Humidifiers Central humidifier reviews and differences in bemis models by Bob Cobe,

The Bemis Whole House humidifier has 3 speeds; the lowest being almost quiet enough for a bedroom use, the medium fairly loud, and the high is like a turbo. The higher the speed, however, the more moisture you can put into the house.

The difference among the lower priced models like the Bemis H12 series is purely a difference in color. They all have a single 2.75 gallon water tank on the left side and can put as much as 12 gallons of water per day into the house.
The higher end Bemis humidifiers such as the Bemis 447 and the Bemis 496 are quite similar to each other. Both have a water tank on each side that adds 4" to the width of the humidifier to double the water capacity.
To fill the water tank, you lift it up, bring it over to a sink, connect the 2 foot included tube to the faucet and turn on the water. Then replace the filled humidifier tank. The tanks have a handle on both the top and the bottom for easier handling which is necessary because a filled humidifier tank weighs 24 pounds.
Both the single and double tank Bemis humidifiers can produce 12 gallons of humidity per day. However, with the 2 tanks you can fill both at the same time and they will probably last 12 hours, whereas with the single tank, you may need in-between fillings.
Both machines turn off when empty and signal with a refill light.
I have been operating my Bemis humidifier for about 3 months and have been adding a capful of their antibacterial solution (you don't have to have the Bemis brand, there are many other solutions that are identical on the market). I have not had to clean it yet even though the directions indicate more frequent cleaning. My unit neither emits smells nor feels slimy, both of which, are conditions produced when mold is present. I think that I will be able to just clean it at the end of the season and replace the filter at the same time.
The size of my 2-story home is about 2400 square feet. If I place the humidifier on the first floor near the upstairs stairway, I can raise the dry normal humidity of 22% up to 33% on the first floor and 31% on the second floor. Before when I had tried a single room humidifier in my bedroom, I was only able to raise it to 33% - 35%. Obviously on rainy days or higher humidity day I was able to raise the inside humidity above those level.
I fill the water tank first thing in the morning and then refill as much as it will take before I leave for work. And when I return from work I fill it again and then a final filling before I go to bed. With this method of filling I am able to put about 10 gallons of moisture per day into my house. My Bemis humidifier unit is set on the middle speed and rarely turns off by itself since I have the humidistat set higher than the machine is able to achieve.
You can find Bemis humidifiers at