Here is someone building a fogger, it gives you the idea you can use 3-4 in plactic ducting with a 3-4 in computer fan etc.
Not sure how to attach videos
https://www.youtube.com/watch?v=Rl2eIk2RlrI
Google VPD
Vapor pressure deficit on cannabis
Seems a little scary like you would invite PM but done correctly with out huge swings all is good.
Humidity keeps the stomata open and the leaves working in conjuction with roots.