Depending on your living situation and your local laws, smoking weed in your apartment can sometimes pose a bit of a challenge - the smell of weed is very distinctive, easily recognizable by almost anyone, and readily travels great distances, especially in closed buildings. If you're living in a multi-unit building, you may be concerned that your neighbors will be able to sense the smell of the burning herb, pinpoint the location it's coming from and report you to the landlord, bringing all sorts of trouble your way. Or you may just be worried about the smell accumulating in your room and getting permanently stuck in the carpeting, furniture, and walls, alerting any guests of your recreational activities.
The legal aspects of smoking at home are obviously something you'll have to research for yourself, as they differ greatly depending on your state/region. You'll also want to check your leasing or renting agreement and see if there's a no-smoking clause included. Even if the legality of cannabis is not an issue for you and you live in a single-unit building, a no-smoking clause does forbid you from smoking and even though you're very unlikely to get caught, if you do, there may be consequences. Currently in Washington DC it is illegal to smoke cannabis in public.
How to Smoke Discreetly
Fortunately, there are ways to use weed discreetly - either by switching to a more discreet way of consumption or by directly focusing on reducing the amount of smoke given off. In many cases, smoking discretely is more of a 'peace of mind' thing - even if the chances of your neighbors 'catching' you smoking weed, reporting you to your landlord and you getting evicted are very, very slim, that worry on the back of your mind can ruin your smoking sessions and ironically lead to more paranoia then relaxation. Here are some ways to smoke more discreetly:
Use A Homemade or Commercoial Sploof
A sploof is a short piece of tube with a filter on one end. The filter can be any clothing material or a piece of tissue paper, tightly secured with a rubber band. Using a sploof simply involves exhaling the smoke through it. Simple tissue paper sploofs don't work particularly well and may only create the illusion that you're reducing your smoke output. Wetting the filter fabric can increase the filtration. There is a way to make the sploof highly effective - by incorporating some activated carbon in it. Activated carbon/charcoal is readily available in pet stores and often used for aquariums. Creating a carbon sploof does take some creativity and there are many designs online, using vitamin bottles for example. Or you can simply fill a regular sploof tube with some carbon and then exhale while keeping it vertical as to not spill the carbon particles.
Buy A Home Air Purifier
Investing in an air purifier and turning it on in a small room after making sure that all the vents of the room are sealed well with tape, can largely solve your smell problems. Make sure to get a model that incorporates a carbon filter and/or an ozone generator. Mechanical filters designed to remove dust and pollen from the air won't really do an adequate job of removing the smell from the air and are not designed to do so.
Open A Window
Windows can help you blow the smoke out, and if the conditions are favorable, can leave your room completely smell-free. This works best if it's cold outside, or at least colder than the temperature of your room. In that case, the hot air from your room will leave from the upper half of the window, while cold air will enter from the bottom. Exhaling the smoke from the top of the window will carry all of the smoke out. If there's no temperature difference between the inside air and the outside, or if it's hotter outside, it can be very difficult to utilize a window properly and in that case, it's best to focus on other methods of smoke mitigation.
Switch to Other Methods of Consuming Cannabis
The vapor from dabbing concentrate does have a smell, but it's not the typical 'weedy' smell - almost no one will attribute the smell of distillate concentrates to weed. Edibles are obviously another great option. Dry herb vaporizers aren't completely smell-free, but their vapor smells significantly less than a typical smoke.