Zero psig is the same as which condition?

Zero psig is the same as which condition?

• A. Atmospheric pressure
• B. 0 psig
• C. 0 psia
• D. Vacuum

Answer: (A)

Zero psig means the pressure inside a system is equal to the surrounding ambient air. Gauge pressure (psig) measures how much pressure is above atmospheric pressure, so when the gauge reads zero, the absolute pressure equals the ambient atmospheric pressure. At sea level that’s about 14.7 psi, not zero. This is different from 0 psia, which would be a true vacuum with no pressure at all, and from a vacuum condition itself, which would be well below atmospheric pressure and would show negative gauge pressure on a psig gauge. So zero psig corresponds to atmospheric pressure.

Zero psig means the pressure inside a system is equal to the surrounding ambient air. Gauge pressure (psig) measures how much pressure is above atmospheric pressure, so when the gauge reads zero, the absolute pressure equals the ambient atmospheric pressure. At sea level that’s about 14.7 psi, not zero. This is different from 0 psia, which would be a true vacuum with no pressure at all, and from a vacuum condition itself, which would be well below atmospheric pressure and would show negative gauge pressure on a psig gauge. So zero psig corresponds to atmospheric pressure.