Ventilation system for a protective suit

1. A ventilation system for a protective suit, including in combination:

a protective suit to cover the user's body;

a face piece to cover at least the nose or mouth of the user;

an air purifying respirator to draw air from outside the protective suit through a filter, and to supply filtered breathing air via a breathing hose to a space within the face piece, and to supply filtered ventilating air via a ventilating hose to the interior of the protective suit;

a ventilation valve in the ventilating hose automatically operable to close the ventilation valve only during periods of high breathing demand to counter a pressure drop inside the face piece.

2. A ventilation system according to claim 1 , where the valve closes when the pressure drop across the filter exceeds a predetermined value, the flow rate exceeds a predetermined value, or the pressure inside the mask falls below a predetermined value, or any combination of these parameters.

3. A ventilation system according to claim 1 , further including a processor to receive signals from sensors associated with the system, and control the automatic operation of the ventilation valve.

4. A ventilation system according to claim 3 , where the signals received from the sensors include a signal representing the pressure drop across the filter, the air flow rate through the respirator or the breathing hose, or the air pressure inside the mask.

5. A ventilation system according to claim 1 , where the valve operates between two states.

6. A ventilation system according to claim 5 , where the valve operates progressively between the two states.

7. A ventilation system according to claim 1 , where the air purifying respirator operates to respond to breathing demand and increase flow to the face piece when breathing demand increases.

8. A ventilation system according to claim 1 , where the air purifying respirator is worn in a harness and is positioned inside the back of the protective suit where space is provided by an extension.

9. A ventilation system according to claim 8 , where a port is provided in the extension for air to be drawn in from outside the protective suit by the air purifying respirator.

10. A ventilation system according to claim 9 , where the filter is outside the suit and screwed to a spigot extending from the pump unit through the port.

11. A gas tight protective suit to cover a user's body, the suit comprising:

a rear extension;

a pump unit worn in a harness, the pump unit worn in a harness being held in the rear extension; and

a port in the rear extension for air to be drawn in from outside the protective suit by an air purifying respirator;

wherein an air-tight connection is made around the port when a filter is properly connected to the pump unit so that no air may pass through the port without passing through the filter; the gas tight protective suit further comprising a ventilation system including a protective suit to cover the user's body; a face piece to cover at least the nose or mouth of the user; an air purifying respirator to draw air from outside the protective suit through a filter, and to supply filtered breathing air via a breathing hose to a space within the face piece, and to supply filtered ventilating air via a ventilating hose to the interior of the protective suit; a ventilation valve in the ventilating hose automatically operable to close the ventilation valve only during periods of high breathing demand to counter a pressure drop inside the face piece.