Pressurize the box

If the box does not maintain pressure, try sealing the edges of the box with clear tape that covers the edges where they connect. 

If testing shows that there is still a problem, ascertain where the leak is coming from and apply more epoxy or silicone. If you are using silicone and t need more viscosity, you can cut it with xylene before pouring so that it will be more amenable to filling in all the small spaces. 

Many systems have a small dedicated compressor to keep the enclosure s pressure up as a safety measure. Simple circuitry could be added for this. If the pressure falls to a preset level, a pressure switch will turn on the compressor to keep it above the set level. 

Other details of circuit fabrication are shown in the photos. The physical circuit layout can vary according to the size and shape of the box used. We used several circuit platforms due to limited box space. The whole of the circuit could be laid out on one flat surface with enough space to make soldering and making connections comfortable and easy. 

Test all circuits before placing them in the box to get a good idea of how each particular circuit works. 

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