What is considered the perfect absolute vacuum?

The perfect absolute vacuum is defined as a state where there are no particles of matter present, resulting in zero pressure. In practical terms, this means there are no gas molecules in the space, which corresponds to a pressure reading of 0 inches of mercury (inHg) absolute.

When measuring vacuum, absolute pressure is taken relative to a perfect vacuum, not relative to atmospheric pressure. A reading of 0" H G Absolute indicates that there is no pressure exerted by any gas, reflecting the ideal situation of a perfect vacuum. Any other measurements, such as 0.5", 1", or 2" H G, indicate the presence of some residual pressure, meaning those states cannot be considered as perfect vacuums. Therefore, the choice representing 0" H G Absolute accurately reflects the concept of a perfect absolute vacuum.