Controlling odors and smells from smelly plants is a very popular topic among indoor gardeners, and Space Buckets are not the exception. Even though there are many options for reducing/removing the odors some plants exhibit, it is difficult to assure 100% 'odor proofness.' For this reason, the bucket community never recommends growing in high risk situations. It's advised against growing offensive plants, especially when others inside the home may have an issue with it, and one should also be at least acquainted with the laws and penalties of the jurisdiction in which they reside.
Inline fans with filters are the best way to keep odors at bay
The most effective solution for controlling plant odors in Space Bucket gardens are inline fans with a specially designed filter. These are the same filters that tent growers use, and because of that they tend to be bulky, expensive, quite loud and is another piece of equipment using electricity. The upside is that inline fans are exceptionally powerful, and thus can filter the air extracted from one or many interconnected buckets.
A 4 inch inline fan with a capacity of 300m3/h should be more than enough for any Space Bucket. These inline fans are a centrifugal type fan, and are very effective by design at creating pressure, which is what is needed to push air through a carbon filter. For this reason cheaper DIY solutions using PC fans are pretty difficult to make effective.
Bucketeers can choose to build their own filters, which is usually not very effective for odors. There are many versions of DIY filters floating around the Internet, but none has proven to be really useful. The general idea is to stack two pencil cup holders with activated carbon in between. The problem is that PC fans are not powerful enough to make a difference, and even line-voltage fans will struggle to move the air through the carbon. A very powerful fan may be sufficient, but at that point an inline fan would be a smarter choice.
One supplemental option for activated carbon filters is ONA gel, a material that masks the smell in the room that is present. This won't remove the odor from the ambient, but it will change its appearance. For this reason, a combination of ONA gel and inline fan + filter is the safest bet for smell concerned bucketeers. The apple crumble version of ONA gel is usually the most effective and recommended.