The differential gas pressure proving method as developed and patented by Medem operates by measuring the pressure differentially across the inlet and the outlet of a gas isolation valve using micro transducers. All other systems can only see the gas pressure when the valve is open.

1. Differential proving enables the supply pressure to be measured before the associated isolation valve is opened. This means that in the event of gas over pressure or under pressure the valve would remain safely shut and reported on the system LCD. Therefore only the differential gas pressure proving method can be considered to be truly fail safe.

2. This method is dynamic in that it takes into account any supply pressure changes that could be temporarily created by increased demand such as a boiler firing. Such transient changes in pressure would have the potential to cause other methods to isolate the gas supply needlessly.

3. Some other gas pressure proving methods can fail to identify a gas leak because they have to be set on installation and if the supply pressure at the time of setting is even slightly higher than in subsequent use then a leak can be missed during test.