can filters have always worked for me.
I have had 1.5lbs hanging in my closet for a only afew hours while 10-15 police officers were standing on my driveway 30ft away arresting a drunk vagrant at 3am

and that was with the little can33.
i recently 'upgraded' to the can66... still no smell that i can (or the cops that pull in front of the house) detect.