Grow room and Flowering

Im very excited to start flowering my blue dream haze this afternoon and turn the light to 12/12. Ive sealed up all windows and doorways to prevent any light leaks but I do have a question about fresh air and humidity. If the room is sealed how do I get fresh air in and humidity out? please keep in mind that they room does not have an AC vent in it. Thank you guys

Room and Plant info
I have 2 plants - both blue dream haze plants in fox farm soil
Light - 150 W Sodium
1 Desk Fan & ! stand up fan
Using a stand up shower that has been lined with mylar.

hey bro. I'm excited to hear you starting flowering. Set up the fan to blow new air in on the bottom one side, and one blowing on the top canopy. Keep the fans ocillating. How big are they now?

Right now they stand at 21" tall . Will this take care if the humidity too?