5.6.1 Before each tank is crude oil washed, the
oxygen level shall be determined at a point 1 m below the deck and
at the middle region of the ullage space and neither of these determinations
shall exceed 8% by volume. Where tanks have complete or partial wash
bulkhead, the determination should be taken from similar levels in
each section of the tank. The oxygen content and pressure of the inert
gas being delivered during the washing process should be continuously
recorded (see regulation 62.16.1.1 and .2).
5.6.2 If, during the crude oil washing:
then washing must be stopped until satisfactory conditions are
restored. Operators should also be guided by 4.5.2.