That indicates to me that there is more air going in than being drawn out. The real question is are you moving enough air out or too much in? You need to find your balance point. Are you controlling temps and humidity? That can influence the amount of air you wish to flow as well. Plenty of resources available here concerning ventilation and lighting basics. Sounds like it's time to bone up. (search)
Learn about CFM and the cubic are of your tent. I personally tend to go big and throttle it down to what I need. Calculated at the appropriate CFM for the space and load of the system. Then oversize it. My fans run quieter as well.
Also you need a free flowing exhaust. Free of obstructions and restriction to achieve it's design or you must allow for that as well.
End result you want fresh air (CO2), heat, and humidity control as well. Are you dealing with capturing and treating odors as well as general air quality? Is your tent in a controlled environment? Or are you controlling the environment within? Not just a simple answer really. Many ways to skin that cat as it were.
thanks mate the humidity is fine just haveing probs keeping the temp up.