What is a likely cause if the output pressure of a filter is significantly lower than the input pressure?

• A. Excessively clean air
• B. Overheating
• C. Contamination
• D. Higher humidity

Answer: (C)

When air passes through a filter, the media is designed to let air through while catching dirt and particles. As the filter collects contaminants, it becomes clogged, which increases resistance to flow. That added resistance causes the pressure to drop between the input and output, so the downstream or output pressure falls significantly. The most direct reason for a noticeably lower output pressure is the buildup of contaminants clogging the filter, signaling it needs cleaning or replacement to restore proper flow.

Excessively clean air wouldn’t create a pressure drop because there’s nothing blocking flow. Overheating isn’t a typical cause of a large differential across a filter, and while higher humidity can contribute to moisture-related blockages, contamination is the primary factor that directly reduces output pressure.