ASTM E 1782 Standard Test Method for Determining Vapor Pressure by Thermal Analysis recommends use of a 50–75 m pinhole for pressures between 5 kPa and 2 MPa. At pressures below 5 kPa using the recommended pinhole range, boiling endotherms become increasingly broad [7], as illustrated by the dashed non-vertical leading edge of the boiling endotherm in Fig. 1.