The pressure in the service tunnel is maintained within a range from 2,000 pascals near the ventilation shafts to 500 pascals at the midpoint.
It will have to be measured in pascals and kilopascals instead of millimetres of mercury.
The pascal is in this category.
In contrast, the metric system has a special name for pressurethe pascal.
Usually the pressure is also lowered in this stage to encourage desorption (typically in the range of microbars, or fractions of a pascal).
