Sentence:  Over a temperature range from 25 to 200 * * f and at pressures up to 250 atm , an overload of 300 psi , applied for a period of one day , results in an uncertainty in the <WSD>pressure</WSD> of , at most , one millimeter of mercury . 
Meaning of the word marked with <WSD> tags:  the force applied to a unit area of surface; measured in pascals (SI unit) or in dynes (cgs unit)