A survey of the principles for primary standards for atmospheric halogenated-hydrocarbon-leaks

Abstract

Albeit the utilization of halogenated hydrocarbons in new devices is suppressed gradually, due to the protection of environment, large amounts of them still remain in existing equipment. It is important for metrology to carry out proper leak measurements of these devices during their service life with traceability to high quality primary standards. Efficient methods have been developed for vacuum leaks (gas outflow into vacuum) but halogenated hydrocarbons leak out into the atmosphere under real conditions. The design of primary standards that meet this condition is considerably more difficult and they are still rather rare. This paper gives an insight into the principles used for these standards, which can be classified into two groups: methods sensitive to the gas species and methods insensitive to the gas species.

Gravimetric flow standard in the vacuum and hermetic modes

“…If we compare the initial atmospheric weighing with the work in the special closable box, the solution is beneficial mainly for secondary standard freon leaks of large values, which usually have a bulky structure. However, it is necessary to realize that this solution was intended especially for them, since there exists a better solution for small and compact leaks: a Mettler Toledo mass comparator; see [29,30].…”