You can get away with it... IT IS CRITICAL TO HAVE ADEQUATE CO2 AND VENTILATION DURING THE LIGHT PERIOD...

Ventilation and air flow are not only critical for bringing in concstant c02 but also for temperature and light proximity to foilage... an HID light 12 inches from your plants will produce TWICE as much bud as a light 24 inches from your plants... more ventilation allows the lights to be closer to the plants

iloveyou