Which symptom may indicate a blocked air filter in an HVAC system?

A blocked air filter in an HVAC system primarily affects the airflow and overall performance of the unit. When the filter is obstructed with dirt and debris, it restricts the amount of air that can pass through the system. This leads to a noticeable decrease in airflow, which can cause the HVAC system to work harder to maintain the desired temperature. Consequently, the system's performance diminishes as it struggles against the increased resistance.

Decreased airflow can also lead to issues such as uneven heating or cooling throughout the space, as well as potential strain on the components of the system, which may shorten its lifespan. Regularly checking and replacing the air filter is crucial to ensure optimal system performance and efficiency.

Although increased humidity, unusual noises, and higher energy costs can be symptoms of HVAC problems, they are not directly indicative of a blocked air filter as clearly as decreased airflow is. Increased humidity could be caused by other factors, such as issues with the system's dehumidification capabilities. Unusual noises may suggest mechanical problems or loose components rather than an air filter blockage. Higher energy costs can result from various inefficiencies in the system, not just an obstructed filter. Thus, decreased airflow and system performance is the most definitive symptom of a blocked air filter