How much FAE?

Hi Shroomok Folk! Really appreciate all your online guidance! I have a Northspore Automated Monotub with a sensor-contolled humidifier and timer controlled FAE fan. As the fan is timer controlled, I dont really know how often/long to run the fan once I start Fruiting Conditions (currently colonization of the substrate is proceeding nicely). I don't have a CO2 monitor. Also, the fan is designed to blow unfiltered room air into the tub; should the intake be filtered?

Thanks much for any help!

Paul K