Hi! One of our professors told us once that in solving problems, always use absolute pressure in the computations. Then one time, I was solving some problems from Dr. Felder's Principles of Chemical Processes book, I often noticed that the pressures used in computations were not always in absolute. That got me confused and I don't know which one to follow. I am guessing that it is a case to case basis, that the type of pressure to be used depends on the problem. In that case, what is the underlying concept that will guide us to correctly select the type of pressure to be used in the computations? Is there a short-hand guide? Thanks!