If your animal is a Boa Constrictor(?you posted this in the general python subforum but your title states Boa?) You should have you humidity around 60/70%. Also you're going to need a larger enclosure for an adult boa unless it's a very small dwarf.

You should change the bedding once dirty..
Edit: I merged both your topics to the boa forum, as they both seem to be about the exact same thing