Hazardous Materials 6th Edition Practice Test

Non‑pressure atmospheric storage tanks are built to hold contents at ambient, or atmospheric, pressure. In theory that means essentially 0 psi gauge, since the contents aren’t being pressurized. In practice, there can be a small positive pressure in the headspace due to vapor pressure of the liquid and temperature changes, but the design limit remains near ambient. That’s why, in many practice contexts, the typical upper bound referenced for these tanks is about 0.5 psi.

So the best choice reflects this very small, near‑ambient pressure — not the higher pressures that would require a pressurized vessel. Higher options like 5 psi or 50 psi indicate vessels designed to carry actual pressure rather than atmospheric conditions.