A chamber assembly (226) for providing a sealed chamber (38) adjacent to a workpiece (28) includes a chamber housing (244), a chamber pressure source (246) and a seal assembly (250). The chamber housing (244) cooperates with the workpiece (28) to define at least a portion of the sealed chamber (38). The chamber pressure source (246) controls a chamber pressure within the sealed chamber (38) to be different than the environmental pressure. The seal assembly (250) seals the chamber housing (244) to the workpiece (28). The seal assembly (250) can include a first seal contact region (270) and a second seal contact region (272) that cooperate to define a seal gap (274) adjacent to at least one of the chamber housing (244) and the workpiece (28). The seal assembly (250) may further include a seal pressure source (276) for controlling a seal pressure within the seal gap (274) so that the seal pressure is different than the chamber pressure and the environmental pressure. The first seal contact region (270) and the second seal contact region (272) cooperate to exert a first force (284) on a surface (278). The seal pressure source (276) generates a second force (286) on the surface (278). The first force (284) is approximately equal in magnitude and opposite in direction to the second force (286).