Patent ID: 7185651

Claim:
A method for regulating air flow, the method comprising: providing a flow path arrangement having a flow regulating valve and a threshold valve, wherein the threshold valve is configured to open at a first vacuum level and to close at a second vacuum level that is less than the first vacuum level; producing a vacuum within the flow path arrangement sufficient to open the threshold valve and to permit a gas to exit the flow path arrangement at a certain flow rate; and maintaining the vacuum above the second vacuum level for at least a certain time to maintain the threshold valve open, with the flow regulating valve regulating the flow rate to be within a certain range while the threshold valve remains open, wherein the first vacuum level is in the range from about 20 cm H 2 O to about 50 cm H 2 O, and wherein the second vacuum level is in the range from about 0 cm H 2 O to about 12 cm H 2 O.