Selection of the method to be adopted is to be conducted by duly considering the required sensitivity. The right choice implies production of a reliable installation, endowed with the necessary sensitivity, at appropriate costs. However cheap it may be, an insufficiently sensitive testing system is of no use whatsoever. Conversely, a system which is too sensitive will generate working costs which are excessive and disproportionate with respect to its true usefulness.

Operationally speaking, it must also be established whether determination of global product leak is sufficient or whether the position of the leak must be determined with precision, or, furthermore, whether the leak value must be correctly quantified.

From the technical and functional angles, the physical conditions of the product to be tested must be analysed. If the product is made up of an elastic material and the pressure variation method is selected, the question of whether variations of product volume shall obtain should be considered, since variation will affect calculation of gas flow. Likewise, temperature must also be considered. Unstable temperatures alter pressure.

If the product is made of plastic, a vacuum method is uneconomic since degassing may take place which cannot be readily controlled.

A key consideration is estimated volume of the tested product: large volumes will reduce the method’s pressure variation sensitivity; on the other hand, the tracer gas method is more costly.