Do you run co2 during dark period, light period or both?

Do you run the co2 during just the light period, or during the dark as well.

Also it recomends that it takes 15 min for my room to fill up. Should i run it every hour for 15 min or every 3 hours, and also again all day or just during lights on?

Thanks

Lights on only. 15 mins every hour