It won’t be right to say that a carbon filter gives you a 100% effective solution against odors of all sorts. However, when it comes to the smell that marijuana leaves behind, a carbon filter can filter out most of the smell but there’s still a chance that there still might be some traces of smell that can be left behind, particularly if you have been smoking in the area and the dust has settled down on furniture around you. You would then need to vacuum those surfaces to make it 100% smell free. However, it would be fair to say that it is at least 85-90% effective in eliminating odours.