A dust collection box for a dust extractor comprising: a housing (1020, 1022); a filter mounted within the housing (1020, 1022); a first air inlet chamber formed within the housing (1020, 1022); an air inlet aperture in a wall of the housing (1020, 1022) which connects to the first air inlet chamber through which air is capable of being drawn into the first air inlet chamber; a second air outlet chamber formed within the housing (1020, 1022); an air outlet aperture formed in the wall of the housing (1020, 1022) which connects to air outlet chamber through which air is capable of being drawn out of the air outlet chamber by a vacuum source; the air inlet chamber and the air outlet chamber being connected by the filter which is located between the air inlet chamber and the air outlet chamber so that air can pass between the air inlet chamber and the air outlet chamber via the filter; characterised in that there is a third air intermediate chamber formed in the housing (1020, 1022); the air inlet chamber and the air outlet chamber being connected by a first part of the filter which is located between the air inlet chamber and the air outlet chamber so that air can pass between the air inlet chamber and the air outlet chamber via the first part of the filter; the air inlet chamber and the air intermediate chamber being connected by a second part of the filter which is located between the air inlet chamber and the air intermediate chamber so that air can pass between the air inlet chamber and the air intermediate chamber via the second part of the filter; a valve located between and connected to the air intermediate chamber and the air outlet chamber through which air must pass in order to move between the air intermediate chamber and the air outlet chamber; an ambient air aperture formed in the wall of the housing (1020, 1022) which connects to the valve through which ambient air is capable of being drawn into the valve; wherein the valve is capable of being switch between a first position where air can freely pass between the intermediate chamber and the air outlet chamber, the valve sealing the ambient air aperture with no air being able to pass through the ambient air aperture; and a second position where the ambient air aperture is open and air can freely pass between the intermediate chamber and the ambient air aperture whilst preventing any from passing between the air intermediate chamber and the air outlet chamber. a housing (1020, 1022); a filter mounted within the housing (1020, 1022); a first air inlet chamber formed within the housing (1020, 1022); an air inlet aperture in a wall of the housing (1020, 1022) which connects to the first air inlet chamber through which air is capable of being drawn into the first air inlet chamber; a second air outlet chamber formed within the housing (1020, 1022); an air outlet aperture formed in the wall of the housing (1020, 1022) which connects to air outlet chamber through which air is capable of being drawn out of the air outlet chamber by a vacuum source; the air inlet chamber and the air outlet chamber being connected by the filter which is located between the air inlet chamber and the air outlet chamber so that air can pass between the air inlet chamber and the air outlet chamber via the filter; characterised in that there is a third air intermediate chamber formed in the housing (1020, 1022); the air inlet chamber and the air outlet chamber being connected by a first part of the filter which is located between the air inlet chamber and the air outlet chamber so that air can pass between the air inlet chamber and the air outlet chamber via the first part of the filter; the air inlet chamber and the air intermediate chamber being connected by a second part of the filter which is located between the air inlet chamber and the air intermediate chamber so that air can pass between the air inlet chamber and the air intermediate chamber via the second part of the filter; a valve located between and connected to the air intermediate chamber and the air outlet chamber through which air must pass in order to move between the air intermediate chamber and the air outlet chamber; an ambient air aperture formed in the wall of the housing (1020, 1022) which connects to the valve through which ambient air is capable of being drawn into the valve; wherein the valve is capable of being switch between a first position where air can freely pass between the intermediate chamber and the air outlet chamber, the valve sealing the ambient air aperture with no air being able to pass through the ambient air aperture; and a second position where the ambient air aperture is open and air can freely pass between the intermediate chamber and the ambient air aperture whilst preventing any from passing between the air intermediate chamber and the air outlet chamber.