TerraBloom ECMF-100, Quiet 4 Inch Inline Duct Fan with Variable Speed Controller – Ventilation Exhaust Fan for Heating Cooling Booster and Grow Tents https://www.amazon.com/dp/B07JNGS2V7/ref=cm_sw_r_apan_glt_i_ZNQ10T3RJWMS3618Y84Y?_encoding=UTF8&psc=1

The in and out ducts are different sizes, I just modled and printed an adapter. It fits the filter snugly. I usually keep it on level 1 or 2 when not in use, 4-5 while printing the fan gets a little too loud at 6-8 for me to tune it out. I've asked several people and they couldn't smell anything in the small office I have it in.

VIVOSUN 4 Inch Air Carbon Filter Smellines Control with Australia Virgin Charcoal for Inline Duct Fan, Grow Tent, Pre-filter Included, Reversible Flange 4" x 14" https://www.amazon.com/dp/B01DXYMBU6/ref=cm_sw_r_apan_glt_i_FZV0VFRSPXXT22F5GSG4?_encoding=UTF8&psc=1VIVOSUN 4 Inch Air Carbon Filter Smellines Control with Australia Virgin Charcoal for Inline Duct Fan, Grow Tent, Pre-filter Included, Reversible Flange 4" x 14" https://www.amazon.com/dp/B01DXYMBU6/ref=cm_sw_r_apan_glt_i_FZV0VFRSPXXT22F5GSG4?_encoding=UTF8&psc=1

VIVOSUN 4 Inch Air Carbon Filter Odor Control with Australia Virgin Charcoal for Inline Fan, Pre-filter Included, Reversible Flange https://www.amazon.com/dp/B01DXYMBU6?ref=yo_pop_ma_swf