turn gas petcock off,the gas tank is vented,take a piece of plastic bag and use a hair tie to hold the bag tight around the base of the gas cap. close choke on carb,take a piece of plastic bag and wrap around airfilter plastic and use a hair tie or rubber band to hold bag around airfilter. put a piece of tape around the cable that goes into the top of the carb(tape can stay on). find a plug of some sort to plug the end of your muffler(you dont have to do this one). now if you do this stuff it will get rid of most of the gas smell in your apartment,trust me i do all of this on my bike when i bring it and keep my bike in my living room. most inportant think to remember is to take this stuff off the bike before bringing outside and starting it or it wont run right. if you dont do these things gas fumes will linger around your house and a spark may light your gas fumes and boom,but usually only happens with gas appliances with pilot lights: like gas stoves or gas hot water tanks.but still the gas fumes can make you sick. if you have any questions i will be happy to answer them.
Karl
covering the gas cap is the most important. next is airfilter.