I have engineered almost everything I use, but here's one that solved a unique problem I had quite a few years back.
I wanted to exhaust the hot air from BOTH my veg room AND flower room and scrub it at the same time, did not want to make a darkroom vent (keeps light out from each room) and did not want to run alot of hoses or ducts.
I searched around and did not find what I needed, so I made my own.
Voila!
The 'Carbon Coffin'
"... the final resting place of dank odors"
Anyways I used it for a number of years and I only had to replace the super activated carbon about every 12-15 months on average. Worked like a charm. (Had some LEO about 4-5 ft from my exhaust and they had no clue.)
My newer designs are alot more complex and work even better, I may show them on here one day, who knows.
A few pics here show the basic layout and the scrubber inner frame(before it was covered with the outer layer of wire frame and nylon and filled with carbon.