There are a number of things you can do to eliminate or at least reduce the smell of burning weed. Cannabis smoke does not stay on clothes and furniture as long as tobacco smoke, but steps to reduce the smell are useful, even if only as a precautionary measure.
What causes the smell?
Most of the smell comes from the idle smoke burning from a joint while it is being passed or when you are holding a hit in your lungs. This is why exhaling into a toilet roll with Bounce dryer sheets rubber bound or taped to the end doesn’t work, along with techniques like exhaling into a bag or holding the entire hit in until nothing comes out when exhaling.
Vaporizing can reduce at least 90% of the smell
A vaporizer is a device that heats up a substance without burning it. Placing Cannabis in a vaporizer for instance, will result in the active cannabinoids (the “chemicals” that get you high) turning into vapor which is inhaled and held in the lungs. This usually looks like a very fine wisp of white vapor. It has the aroma and taste of the bud itself. It has been described as “floral” and resembles a fragrance.
The smell dissipates from the air in about 5-10 minutes, and does not stick to clothes or furniture like smoke. In my experience, most people do not associate the aroma of Cannabis vapor with anything suspicious, even if it is strong. It is not as easy to recognize as the smell of burning paper and weed.
A vaporizer costs anywhere from $50 up. If you go this route, invest in a good quality vaporizer. Besides allowing you to smoke indoors and removing most of the smell, vaporizing is safer than smoking (ref), saves you a lot of money by conserving bud, and in my experience gets you much higher than any form of ingestion except oral (brownies, etc.)
Carbon Filter or Standard Air Filter
A carbon filter is a fan that passes air through a layer of activated charcoal. This adsorbs (chemically binds to, instead of absorb which means to stick to) noxious gases in the air, effectively cleaning air in the room from most smells.
The basic scenario is to close your room off and turn the carbon filter on. Smoke, and exhale into the general direction of the filter. Air will constantly be passed through the filter and cleaned, “scrubbing” the air clean within 10-30 minutes (depending on how many times per minute the air is being cycled in the room.)
In my experience, carbon filters do great at cleaning air in a room, but the smell of smoke remains on your clothes a little, and tobacco smoke is not filtered thoroughly.
Carbon filters work well, but unless you invest in a quality air filter that is powerful (2-3x the size advertised for your room), a dedicated commercial carbon filter with a fan (very noisy!), or create your own for your room or a smoking room in the house, you will likely not benefit too much here.
Most standard home air filters contain a thin sheet of carbon which is better than nothing, but may not be enough for the heavy smoker. Commercial heavy duty carbon filters are designed for the sole purpose of moving air through a thick layer of carbon pellets (as opposed to a sheet) and letting that air make contact with the carbon for a minimum amount of time to ensure maximum adsorption.
A carbon filter and a vaporizer together are an excellent combo for smoking indoors when you don’t want others in the house to smell anything.
This method involves submerging your bud in lukewarm water and letting it sit in a cool dark place. Change the water every 6-12 hours for 2 days. Then take the bud out and let it dry near a fan or by placing it on something modestly warm such as a computer router/modem or the top of a fridge.
This causes a lot of the smell and other water soluble things in the bud to be eliminated. When the bud is dry, it will have lost a little bit of weight, meaning potency has increased (more trichomes squeezed into a smaller area.) It will also lose almost all bag appeal, aroma and subsequently taste.
So why do it? Because the bud now smells almost nothing like pot. It will have a distinct aroma, faintly like weed, but mostly like smoke (and burning paper.) Mix some in with tobacco and the smell is masked completely. The bud will also be much smoother, as you will be smoking a lot less elements present in the little leaves on the plant.
Water curing is also a great way to cook with weed when you don’t want any marijuana smell or aftertaste, but personally, I like the taste.
ONA Gel, Febreze/Clenzaire, Ozium and Other Odor-Eliminating
These sprays contain a compound that is supposed to bind to odor causing chemicals in the air, chemically rendering them scent-less. They come in the form of a spray or as gel in a can or bucket that you keep open.
They work but they leave their own distinct smells which may be suspicious. For example, if you get stopped driving and the officer notices your car reeks of Febreze or Ozium, he or she might become suspicious as to what smell you’re hiding. Similarly to somebody lighting up a cigarette as police are walking to their car, although in contrast to the sprays/gels, cigarette smoke merely masks the smell instead of eliminating it.
These are useful to have around and work a little better if there is air flow in the room, such as from a fan or window.