I have a small cool mist humidifier for my office (where I store my guitars) but for the main shop (1600 sq ft.) I spent a lot of time getting quotes and basically wasting time as the humidity continued to drop.
In a bit of a hail Mary...I took a hot plate and pans of water and made my own humidifier. It turns out that it worked very well to just steam water into the room from those pans.
But let me explain further. What I call a "hot plate" is really an aluminum plate with a couple of silicone heat blankets and a type J theromocouple attached to a small heat controller. The plate measures about 1" thick by 6" wide and is about 24" long. The pans are those round aluminum pans that you might get a serving of pasta packaged in at a take-out resturant. All this stuff was just sitting on a shelf, leftover from another enterprise but it would be simple to make and control from a wood bending controller, if you have one of those.
I line up four of those pans on the plate and set the temperature of the plate to 140F... and simply keep the pans filled with water. I check the humidity a couple of times a day and crank it up or down 25 degrees as required. Sounds hokey....ok....it LOOKS hokey but I haven't had a thought to replace it since I set it up. I figure if I but a REAL humidifier and it breaks I won't know how to fix it. This way, I'm working with stuff I understand.
No filters, no cleaning. Simple.You wouldn't set this up in a house but I thought I'd post this idea for shops.