Need Inline Fan Help.

First time doing this. Got a 4x4x7 tent with a 600w hps that is ducted out the sides. I also have two 6" inline fans, intake with hepa filter and exhaust with carbon filter. Exhaust is high, intake down low. How often do I need to have the fans on to refresh the air in the tent? If it is often, what device would I use?

I am reading that you have an air cooled hood. As the light is sealed, you don't need any filters or scrubbers on the tubes leading to and from the light as there is no mechanism for the smell to get into the light. Install the fan downstream of the light so air is pulled through the light.

Now use your other fan to simply exhaust the hot air from inside the tent and out through the carbon filter. You need some way for the air to get in (and sure, a hepa filter on it would be nice).

You don't need an intake fan... ever. Air is like all matter in the universe.. If it leaves, something has to take its place. In fact, it CAN"T leave until something does take its place. To control the fan your going to need a thermostat controller. You set the temp and the fan kicks on when its exceeded. Your looking at around $65-75 bucks for one made by CAP

Thanks for the info. That thermostat is exactly what I wanted...a plug in type. I do have passive air intakes on the tent, but I also have a 6" to 4" reducer with hepa filter to help out with the intake of clean air. I may not use it, but since I all ready bought it, might as well try it right?