No it s not PSI,a pressure is given in pascal, the standard unit for pressure is the Pascal, which is a Newton per square meter
as I have said before this question date of 1947!!not surprising why they are all bolt with grey hair at the CAA!
And do not be confused with PSI(pound per square inch) which is not ISO...
The SI unit of pressure is the pascal, symbol Pa, the special name given to a pressure of one newton per square metre (N/m2). The relationships between the pascal and some other pressure units are shown in the table but note that not all are, or can be, expressed exactly. Note also that the term standard atmosphere is not a pressure unit(5).
Unit Symbol No. of Pascals
bar bar 1 x 105 Pa (exactly)
millibar(1) mbar 100 Pa (exactly)
hectopascal(1) hPa 100 Pa (exactly)
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conventional millimetre of mercury(2,3) mmHg 133.322... Pa
conventional inch of mercury(2,3) inHg 3 386.39... Pa
torr(4) torr 101325/760 Pa (exactly)
pound-force per square inch lbf/in2 6 894.76... Pa