This document describes procedures to measure outgassing rates from components designed for vacuum chambers and of vacuum chambers as a whole. The outgassing rates are expected to be lower than 10−5 Pa m3 s−1 (10−2 Pa L s−1) at 23 �C and to emerge from devices that are suitable for high or ultra-high vacuum applications. The molecular mass of the outgassing species or vapour is below 300 u.
The upper limit 10−5 Pa m3 s−1 of total outgassing rate is specified independent of the size, the total surface area and texture or state of the outgassing material. If a specific outgassing rate (outgassing rate per area) is determined, the area is not a specific surface area including the surface roughness, but the nominal geometrical one. When it is difficult to determine the nominal geometrical surface area of the sample, such as powders, porous materials, very rough surfaces, or complex devices, mass specific outgassing rate (e.g. outgassing rate per gram) is used.
For many practical applications, it is sufficient to determine the total outgassing rate. If a measuring instrument, which sensitivity is gas species dependent, is used, the total outgassing rate are given in nitrogen equivalent. In cases, however, where the total outgassing rate is too high, the disturbing gas species is identified, and its outgassing rate is measured in order to improve the sample material. This document covers both cases.
Some outgassing molecules can adsorb on a surface with a residence time that is much longer than the total time of measurement. Such molecules cannot be detected by a detecting instrument when there is no direct line of sight. This is considered as a surface effect and surface analytical investigations are more useful than general outgassing rate measurements considered here. Also, molecules that are released from the surface by irradiation of UV light...