typical barometric pressure
The weight of the atmosphere on the surface of the mercury exerts a pressure transmitted through the fluid, forcing it to rise. The greater the weight, the higher the rise. The barometric pressure seldom goes above 31 inches or drops below 29 inches. Normal sea-level pressure is 29.92 inches.o a metric unit has been defined to describe normal atmospheric pressure, called a bar, and the instrument becomes a barometer.. Actually, normal average sea-level pressure is 1.01325 bars, or 1,013.25 millibars (mb).