We always recommend raising humidity for RI at the places I have worked. This goes for dogs, cats, small animals, etc. While it does make sense that heat plus humidity equals bacteria breeding....think about where you are trying to stop bacterial growth. The lungs and respiratory tract. It is naturally very moist in there already. Breathing in dry air irritates the mucosal lining of the respiratory tract, which can complicate recovery. Also, higher humidity helps to keep the mucous moist and helps the body dispose of it more efficiently.