National Home Inspector Practice Exam

Which of the following describes partial vapor pressure?

1. Water vapor has a tendency to disperse itself equally in the available air.

2. Water vapor causes new homes to require house wrap.

3. Water vapor is common with forced induction natural gas furnaces.

4. Water vapor is an indication of sick house syndrome.

The correct answer is: Water vapor has a tendency to disperse itself equally in the available air.

Partial vapor pressure refers to the pressure exerted by a specific component of a mixture of gases in a system, in this case, water vapor. The statement that water vapor has a tendency to disperse itself equally in the available air aligns with the principle of diffusion, where gases move from an area of higher concentration to an area of lower concentration until they are evenly distributed. This natural tendency for gases, including water vapor, to mix uniformly in the atmosphere is fundamental to understanding air quality, humidity levels, and the behavior of moisture in residential environments. In contrast, the other options describe related concepts but do not accurately capture the essence of partial vapor pressure. New homes needing house wrap, for example, pertains to moisture management and building envelope performance but does not directly relate to the concept of partial vapor pressure. Similarly, the mention of forced induction natural gas furnaces and sick house syndrome touches on issues of moisture control and indoor air quality but are not definitions or descriptions of partial vapor pressure itself.