It is best to check the dirt level in the bag before each use. For best performance, it is recommended that you change your bag when it is 1/2 to 2/3 full or when the outside of the bag feels firm to the touch. When accumulated, small dust particles can keep the air from circulating; this can reduce the suction in your vacuum. You may need to change your bag more frequently when vacuuming fine dust and debris, pet hair or new carpet. It is also recommended to check your vacuum’s filters at the same time you check the bag. *Did you know that your vacuum, bagless or bagged, has filters that should be checked frequently! Depending on your household, your friends at BISSELL recommend cleaning or replacing your filters frequently and more often if you have pets that shed and family/friends that track in dirt and debris. Refer to your BISSELL vacuum owner’s manual for cleaning and replacement instructions.