Humidity trays if large enough will raise the humidity in the whole house.
Two winters ago I was still growing in the basement. I had several large
trays like those used for under washing machines filled with small stones.
I used these under the plants I was growing under HID and MH lighting. I
had several fans moving the air around the basement. I also have a
residential humidifier on the gas furnace.

In the winter when it was cold my windows in the house would fog up. I
never thought much of it then. Last winter (and so far this winter) I
haven't seen any condensation on the windows. The difference is that all
the plants have been relocated into the greenhouse. I never realized how
much water I was putting in the household air when I had the plants in the
basement.

So my point is that humidity trays must be very large to humidify the entire
closed space. In my case it was the entire house.

Good growing,
Gene