Abstract: A vacuum cleaner has wet and dry modes. In dry mode, air containing dust is passed through a multi-stage filter including adjacent subchambers containing a liquid for removing microscopic dust from the incoming air. The liquid is prevented from being exhausted from the vacuum cleaner with the exhausted air and is returned to the subchambers. In wet mode, a float and float guide cause a difference in pressure when the vacuum cleaner is filled with liquid. The pressure difference is sensed to actuate an electric circuit breaker to prevent overflow.