Residential HVAC Installation Practice Exam 2025 - Free HVAC Practice Questions and Study Guide

The primary function of a furnace filter is to trap dust and allergens from circulating air. This is crucial in maintaining indoor air quality, as the filter captures various particles that can be harmful or irritating to occupants, such as dust, pollen, pet dander, and other allergens. By filtering out these contaminants, the system ensures that the air being circulated throughout the living space is cleaner and healthier to breathe.

While enhancing heating efficiency can be an indirect benefit of keeping the air clean—since a clogged filter can restrict airflow and reduce system efficiency—the main purpose of the filter itself is focused on air purification. Sound levels during operation are generally influenced by other factors, and while some filters may impact noise minimally, this is not their primary purpose. Regulating air pressure in the ducts may involve different components like dampers or blower fans, rather than the furnace filter itself. Thus, the correct understanding of a furnace filter's role lies in its primary function of trapping particulates to enhance air quality.