Mr. Bogart I hope this helps.
Take a look at the picture in this
link of the installation and maintenance instructions it will help you visualize how to install the fan correctly. Note how the fans are conveniently located at the end of the duct line.
There is also the rather significant matter of the difference between negative and positive pressure systems. By placing the exhaust fan at the end of the duct line you create a negative pressure system. What that means is that the pressure inside the grow box and carbon filter is lower than the pressure outside the boxes. A negative pressure system avoids the potential problem of odor leaks as all air is sucked through the system, including any possible leaks. A negative pressure system also makes the seals on both the grow box door and filter work more efficiently as it sucks them closed rather than blowing them open. A postive pressure system (pushing the air through a grow box and or charcoal filter thereby raising the air pressure to higher than that outside the boxes) has the opposite effect.
Please do install your fans where ever you feel it works best for you.
