What does a 25% pressure drop across an HVAC filter indicate?

A 25% pressure drop across an HVAC filter typically indicates that the filter is becoming obstructed with dirt and debris. As air passes through the filter, it traps particles, and over time, the accumulation of these particles increases airflow resistance. When the pressure drop reaches a significant level, such as 25%, it suggests that the filter is no longer allowing air to flow freely, which can hamper the overall efficiency of the HVAC system.

This drop in pressure is a clear signal that the filter is reaching the end of its effective lifespan and should be replaced. Regular maintenance and timely replacement of filters are essential to ensure the HVAC system operates efficiently, maintains indoor air quality, and prolongs the life of the equipment. It prevents potential issues such as reduced airflow, increased energy consumption, and strain on the system.

Other answer choices refer to different conditions: a pressure drop being indicative of normal operation would generally suggest that the filter is clean and air is flowing easily. Potential blockage might imply some obstruction, but a 25% drop indicates a significant level of blockage, necessitating replacement. Efficient filtration relates to a filter's ability to capture particles without causing excessive pressure drops, which is not the case at this level of pressure drop.