Vapor collection method and apparatus

An apparatus for treating a moving substrate of indefinite length, comprising:

• (a) a control surface in close proximity to a surface of the substrate to define a control gap between the substrate and the control surface;
• (b) a first chamber near the control surface, the first chamber having a gas introduction device;
• (c) a second chamber near the control surface, the second chamber having a gas withdrawal device, such that the control surface and the chambers define a region wherein the adjacent gas phases possess an amount of mass;
• wherein upon inducing transport of at least a portion of said mass within said region:
• M1 means total net time-average mass flow per unit width into or out of the region resulting from pressure gradients,
• M1′ means the total net time-average mass flow of a gas per unit width into the region through the first chamber from the gas introduction device,
• M2 means time-average mass flow per unit width from or into the at least one major surface of the substrate into the region,
• M3 means total net time-average mass flow per unit width into the region resulting from motion of the material, and
• M4 means time-average rate of mass transport through the gas withdrawal device per unit width such that M1+M1′+M2+M3=M4, M1 has a value greater than zero but not greater than 0.25 kg/second/meter and there is a slight inflow of gas into the region.

A method for treating a moving substrate of indefinite length, comprising:

• (a) locating a control surface in close proximity to a surface of the substrate to define a control gap between the substrate and the control surface;
• (b) positioning a first chamber near the control surface, the first chamber having a gas introduction device;
• (c) positioning a second chamber near the control surface, the second chamber having a gas withdrawal device, such that the control surface and the chambers define a region wherein the adjacent gas phases possess an amount of mass;
• and
• (d) inducing transport of at least a portion of the mass within the region, such that when M1 means total net time-average mass flow per unit width into or out of the region resulting from pressure gradients,
• M1′ means the total net time-average mass flow of a gas per unit width into the region through the first chamber from the gas introduction device,
• M2 means time-average mass flow per unit width from or into the at least one major surface of the substrate into the region,
• M3 means total net time-average mass flow per unit width into the region resulting from motion of the material, and
• M4 means time-average rate of mass transport through the gas withdrawal device per unit width such that M1+M1′+M2+M3=M4, M1 has a value greater than zero but not greater than 0.25 kg/second/meter and there is a slight inflow of gas into the region.