The box emits no smell, the hallway down one side traps loose liter before the cats jump out and keeps the dog from getting treats. It was a blast to make.
Looking in from the back of the shelves during construction. There is a small closet that goes to the adjoining bedroom. I sacrificed part of the closet for shelves in the bathroom and the cat box.
Here you can see the pipes leading from a small bathroom fan to A dedicated vent pipe. That pipe goes up and through the roof. I added power to charge a cordless razor or curlers (do people use those any more?) The blue electrical box behind that pipe houses the timer switch.
NOTE: THIS IMAGE INCLUDES A CONNECTION TO THE BATH TUB VENT STACK. DON'T DO THAT! SEE CHANGES I MADE LATER AT THE END OF THIS SET!
Here is the timer from the front. At one point I was going to put a motion detector in the box. Glad I didn't because there seems to be a natural draw in the box that self clears the air. Not enough to pull heat out of the house. Just a slow steady flow to removes stink.
The box is coated with shellack. Shellack resists soaking in any odor and it's waterproof. On the floor of the box I poured about 1/8" of epoxy in case of spills. The finished box can hold water. 2 inches deep (just had to try for fun)