Final answer:
Pressure tanks should be kept at specific levels of fullness and maintained at a manufacturer-specified PSI for operational safety. Most pressure gauges measure gauge pressure, which is relative to atmospheric pressure and indicates whether a tank is sufficiently pressurized.
Step-by-step explanation:
The statement regarding pressure tanks is related to safety protocols in handling compressed gases. When dealing with pressure tanks, such as scuba tanks, the maintenance of a certain liquid or gas level and pressure is crucial for safety and functionality. Most pressure gauges are designed to read gauge pressure, which is the pressure relative to the atmospheric pressure, and typically reports a positive value when the pressure inside the tank is greater than the atmospheric pressure outside. This helps in knowing when a tank is safely pressurized or requires refilling.
Pressure tanks should typically be kept a certain percentage full to allow for the expansion of the gas, especially under heat which could increase internal pressure. The specific fullness level and required PSI will depend on the type of tank and the gas it contains. The maintenance pressure (in PSI) is often specified by the manufacturer or relevant safety standards to prevent overpressure situations which could result in equipment failure or more serious safety hazards. In our example, a tank designed with a safety factor of 2 can handle up to 400 atmospheres. To understand how hot the gas must get before the cylinder may no longer hold, one would likely need to apply the ideal gas law along with the materials' thermal properties and the safety factor of the cylinder.