Everyone who has grown a substantial crop in their basement will attest to the strong odor the crop produces as the plant matures. Most people have been busted simply because of the strong smell of a mature plant permeating the air around the home in question.
There are a few things that can be done to keep the smell of cannabis down both within and outside the house where it is being grown. Running a hepa filter in the growing area will stop a large amount of the odor, but not all. While the activated charcoal in a hepa filter will stop most of the smell, some ventilation to the outside will also be needed.
Hepa filters come in many sizes and shapes. Some are just the filter, while others incorporate a of fan. If you have the choice, choose the filter with the fan. Most basements have at least one small window, so use it is as the output of the filtered hepa filter. Remove the glass and replace the window with a board with the hepa filter shape cut in. Choose a window that vents to the backyard or a window on the side of the house with low traffic.
Another way to keep the scent down is with eucalyptus. Eucalyptus is great for covering odors and replacing them with the cool scent of the plant. Eucalyptus is also great for keeping the humidity down, an action which negates the growth of mold and fungus, since they both need a damp environment to grow in.
The eucalyptus needed is usually in the form of an oil, which won’t do its job if the surface area is as small as the diameter of the jar it came in. To that end, pour the oil in a wide, shallow pan. This will result in a decreased marijuana odor. The eucalyptus will also reduce the humidity due to its very efficient moisture retention properties.