Negative pressure treatment including mechanical and chemical pump

A negative pressure assembly comprising:

• a drape for covering a dressing site on a patient and capable of maintaining a negative pressure underneath the drape when sealed against skin upon application of a vacuum;
• a sealing element that when applied to the skin cooperates with the drape to define an enclosed volume covered by the drape and surrounded by the sealing element;
• a valve disposed on the drape having a first operating state in which gas exits the enclosed volume through the valve and a second operating state in which gas is precluded from entering or exiting the enclosed volume through the valve;
• and
• a mechanical pump assembly including a pump chamber fluidly connectable to the enclosed volume through the valve when the valve is in the first operating state, and configured to draw air from the enclosed volume into the pump chamber when fluidly connected with the enclosed volume;
• and
• a reactor located with respect to the drape and the sealing element so as to be in fluid communication with the enclosed volume when the drape is covering the dressing site, the reactor being configured to react with oxygen found in air so as to consume the oxygen from the air;
• wherein the valve is a relief valve configured to allow gas from ambient to enter the enclosed volume through the relief valve when a pressure differential between ambient and the enclosed volume is outside a predetermined pressure range.