What is one common reason for poor indoor air quality linked to HVAC systems?

Blocked air filters are a common reason for poor indoor air quality in HVAC systems. Air filters are designed to capture various airborne particles such as dust, pollen, pet dander, and mold spores. When filters become clogged or blocked, they can no longer effectively trap these contaminants, allowing them to circulate throughout the indoor living space.

This stagnation in airflow not only diminishes the efficiency of the HVAC system but also leads to an increased concentration of pollutants in the air, which can aggravate respiratory issues and allergies among building occupants. Furthermore, blocked filters can cause the HVAC system to work harder to pull air through, potentially leading to overheating and system failures. Regularly replacing or cleaning air filters is crucial for maintaining good indoor air quality and ensuring the system operates efficiently.

The other options presented focus on positive aspects of HVAC system operation. Proper humidity maintenance typically contributes to better indoor air quality by preventing mold and maintaining comfort levels. Regular system maintenance ensures that all components function as intended, promoting overall system efficiency and reliability. Using energy-efficient equipment is beneficial for reducing energy consumption and costs but does not directly relate to the quality of indoor air unless it also involves effective filtration and ventilation.