Polishing Grow Room Odors
You don't have to exhaust air from one area to another to eliminate nutrient odors.
This alternative is called 'polishing' the air in the room. It's a simple setup, where you'd put a fan and filter into a corner, leave it on 24/7, and recycle the air in the room over and over through the carbon filter.
It works really well if you can put it in the direct vicinity of the plants, and it won't affect the flavor or aroma of your crop. If you don't have room in a corner, you can hang the entire setup from the ceiling.
We recommend using a short length of ducting between the fan and the filter.
The ducting helps to avoid the fan vibration passing through to the carbon filter. The vibration may cause the carbon at the top to settle, which can possibly allow air to pass through the filter untreated. Even just a few inches of flexible ducting between the fan and the filter is enough to keep this from happening.
Handling noise volume.
The fans that you use for a carbon filter are very powerful fans (this is necessary because it enables them to draw air through the tight packed carbon), and they can be kind of loud depending on your situation.
To quiet the fan down, I'd recommend using 3-4 bungee cords to hang the fan, so it's not directly touching your homes walls, floor, or ceiling. By suspending it with bungee cords, it won't vibrate at all, and this cuts the noise level down substantially. If noise level is a really big deal, our inline duct mufflers can cut the noise level down even more.
The biggest reason people use ducting is that they need to remove heat from a room or tent, and this allows you to draw from, and exhaust to wherever you want. As I mentioned, these are powerful fans, and they work great for moving air from one room to another, or even outside.
If you use a fan/filter combo to exhaust heat to another area, the filters work so effectively that you can move the hot air into another room in your house during the cold winter months, and there will be no fertilizer odors at all, just clean warm air to increase humidity and help heat the house.
But if you don't have a heat issue in the garden, setting it up in a corner to polish the air is probably the better approach.
In an exhaust situation, the fan can be mounted any distance from the filter, even in another room. There is no 'set in stone' way to put this together, you can do it however it serves your purpose. Point A and point B are entirely up to you and your situation.
One big thing to remember when you're exhausting air to another area is that you have to make sure that there is a passive 'intake' somewhere else in the room for air to get into the room as the fan is pulling air out. Without a passive intake, the fan won't be able to move enough air to effectively do it's job. In a tent, the lower passive vents are sufficient, but then you still may have to make sure there is a passive air into the room itself.
One popular way to assemble a fan/filter combo is to put the filter in the room with the plants, then run ducting to vented reflectors, then the fan, and then run the ducting to wherever you're exhausting to. This setup will draw the air into the passive vents, past the plants, through the filter, through the reflector(s), and out of the room. You can find more information about exterior fan/filter venting here.