The ideal humidity level for a babys room is between 40-60% . This range is healthy for the babys body because bacteria have a hard time growing in this range. The Environmental Protection Agency (EPA) recommends a humidity level no higher than 50% to prevent mold growth in the house. Some doctors even recommend keeping the baby room humidity between 50 and 70 percent, but high humidity fosters the growth of bacteria in the air, which can lead to the baby getting sick. Therefore, it is best to keep the babys room at around 50% humidity, and you may be able to bump that up to 55% if youre careful and keep it clean. You can use a whole-home humidification system or a whole-house humidifier to reach this ideal humidity level. It is important to note that aiming a humidifier or diffuser at the babys crib or bed will significantly raise the humidity level around the bed, but the overall humidity of the room will not be as high.