Review on Nature Fresh 8-Pack Charcoal Bamboo Bags - Activated Charcoal Odor Absorber Eliminator Bag (8 x 200g) by Nikki Lewis

They remove odors passively and have no immediate effect. I love the shape and that they have hanging loops. This bag had more than I needed so some of these fit in my car to eliminate odors I can't smell. I placed them near the sources of the smell (around the cat and on the back) which dissipate much faster than before. The only downside is that her power is limited to a small area around her. Don't expect to place them in the corner of your largest room (e.g. hallway or basement) away from the source of the odor and magically eliminate odors that build up there. Essentially, activated charcoal works, but it's not as effective as an odor spray like Febreze. At least there are no unpleasant smells and less work and last longer.