Which moisture entry mechanism involves direct contact with bulk water?

• A. Bulk water
• B. Vapour diffusion
• C. Capillary water
• D. Air-transported moisture

Answer: (A)

Direct contact with liquid water occurs when actual bulk water is touching the surface or infiltrating the assembly, such as leaks, splashes, or flooding. This is different from moisture moving as water vapor through materials (vapour diffusion), or water drawn into pores by capillary action (capillary water), or moisture carried by air (air-transported moisture). The presence of liquid water at the interface is the hallmark of bulk water intrusion, making it the correct mechanism.