Why doesn't my vacuum cleaner seem to pick up all the dust?

That's a good question and depends on what type of vacuum you have.  Here at Cleaning Enterprises we use Sanitaire Commercial vacuums.  We tend to them every day because of the number of houses we clean.  Each vacuum has it's bag replaced and belt and rollers checked.  Any items wound around the roller (hair is a typical culprit) are removed.  The belt is checked for fraying and replaced if there are any signs.  Finally the vacuum is cleaned both top and bottom to remove any dust.  Once every week or so the cord is cleaned so that if it were to rub against a wall or a door it wouldn't leave marks.

However your vacuum may not be like ours.  Yours may be a bagless type.  Many people think these don't need maintenance like the bag variety.  Actually, these can emit more dust than a bag vacuum unless the seals are lubricated and the filters cleaned.  What filters you ask - mine doesn't have filters.  My answer is a definite yes it does - or throw it out!  The vacuum needs to exhaust the air somewhere.  Without a filter, all of the dust and dirt in the vacuum chamber that replaces a bag would come out.

Many people don't clean their filters and over time the vacuum loses suction.  Eventually wearing out the motor.  Look around for filters either at the base of the vacuum chamber or on the sides of the motor housing.  Typically the filters are either foam rubber or some other semi-porous material that lets out air but not dust.  Clean with soap and water and replace.  Ultimately these filters will wear out or wont be able to be cleaned.  Your local vacuum store should have replacement filters.