If you have a humidifier for your kids, you have to put it in the rooms where most of the time it spends.
If you look at a smaller humidifier, it must be kept in mind that only in one room can it be successful. You will want to consider having more than one to ensure that all places in touch with which your baby comes are protected.
In small apartments, it can be useful to buy a wetter so that all areas can be covered immediately if the living room is near the kindergarten.