(2) for single or double-wall tanks emptied of any petroleum products, a pressure test using an inert gas performed in compliance with the following requirements:(a) a safety valve set at not more than 40 kPa capable of discharging the flow from the pressure source must be installed on a tank opening and its operation must be inspected before each test;
(b) the pressure must be measured using a pressure gauge calibrated in units of not more than 1 kPa;
(c) a pressure of at least 30 kPa and not more than 35 kPa must be created inside the tank;
(d) once the temperature has been stabilized and the pressure source removed, the created pressure must be maintained for at least 4 hours; and
(e) in the case of a compartment tank, each compartment must be tested separately, not simultaneously and only when the adjacent compartment is not under pressure.