What unintended consequence can result from underrating a filter?

Underrating a filter refers to selecting a filter with a lower capacity or efficiency than what is necessary for the air handling system. This choice can lead to an inefficiency in the filtration system that alters its performance characteristics. Specifically, underrating a filter can change the efficiency curve, which is a representation of how effectively a filter captures particles of varying sizes.

When a filter’s rating does not match the system's requirements, the airflow may not be adequately filtered, leading to a shift in the efficiency curve. This shift can mean that the filter does not perform as expected under certain conditions, potentially allowing more pollutants to pass through or causing the system to work harder to compensate for the increased load.

In contrast, increased energy costs, higher noise levels, and shorter filter lifespan are potential issues linked to the operational problems caused by an underrating scenario. While these consequences can also occur from using an undersized or inadequate filter, the most direct and immediate result of underrating is the alteration of the efficiency curve which impacts filtration performance directly.