What environmental factors can affect an air filter's lifespan?

The chosen answer identifies humidity, temperature, and airborne pollutants as critical environmental factors influencing an air filter's lifespan. High humidity levels can lead to the growth of mold and mildew within the filter, reducing its effectiveness and increasing the frequency of required changes. Elevated temperatures can also affect the filtration material, causing it to degrade faster. Additionally, the presence of airborne pollutants such as dust, smoke, pollen, and other particulates can clog the filter more quickly, leading to a diminished airflow and increased strain on the HVAC system.

This combination of environmental considerations demonstrates how external conditions can significantly impact both the efficiency and durability of air filters, making them crucial for maintaining optimal indoor air quality and system performance. Other options, while they may relate to air filtration in more abstract ways, do not directly address the immediate, quantifiable factors that affect the lifespan of filters as specified in the correct choice.