by wire connections 28 in the embodiment illustrated a quantity of charcoal 29 is bonded on the lower container member 25 also charcoal may be placed in the void 30 within the container separately or along with bonded in place charcoal another alternative embodiment is illustrated in fig6 with a semiconductor such as a transistor 31 mounted in a container 32 having a base member 33 and a can member 34 the base member normally is an insulator with leads 35 for connection to the transistor 31 which may be a single transistor or a circuit chip with a plurality of transistors and other components prior to sealing the can member to the base member a quantity of charcoal 36 is placed in the can member alternatively the charcoal can be positioned around the transistor and the base member it will be readily understood that the same construction as described in the preceeding embodiments can be utilized for any component which needs to be hermetically sealed in a container after the components and the charcoal have been sealed in the container the device is tested for leaks in the manner described above in one method the device is exposed to a fluid under pressure which can penetrate the container through any existing leak assuming that there is a leak after the external pressure is removed the leaked fluid now under pressure within the container will escape through the leak the presence of such leaked fluid around.