A negative pressure device includes a drape, a wicking element, a sealing element, a reactor, a chamber and an air permeable liquid impervious element. The drape includes an opening and is made from a flexible material that inhibits passage of liquid and air through the drape other than through the opening. The wicking element is covered by the drape. The sealing element surrounds the wicking element and cooperates with the drape to define an enclosed volume covered by the drape and surrounded by the sealing element. The reactor is configured to react with a gas found in air to consume the gas. The chamber is in fluid communication with the reactor and the enclosed volume via the opening. The chamber is configured to maintain a predefined chamber volume while the gas is being consumed from the enclosed volume.