What is the most common type of filter used in an HVAC system?

The most common type of filter used in HVAC systems is typically the fiberglass filter. This type of filter is widely utilized due to its cost-effectiveness and efficiency in capturing larger particles such as dust, lint, and dirt, which helps maintain good air quality and protects the HVAC system's components.

Fiberglass filters work by using a mat of fiberglass fibers that create a barrier for particles. They are relatively low in resistance, allowing for good airflow, which is crucial for the efficiency of HVAC systems. Although they do not provide the highest level of filtration compared to other types, such as HEPA or activated carbon filters, their balance of cost and performance makes them a popular choice for residential and commercial applications.

Activated carbon filters are more specialized for removing odors and certain gases but are not as commonly found as the primary filter in standard systems. HEPA filters offer superior filtration but are typically used in specialized applications, including hospitals and cleanrooms, due to their higher costs and resistance to airflow. Viscous impingement filters, while effective for certain applications, are not as broadly used in typical HVAC setups. This context helps highlight why fiberglass filters are the predominant choice in many HVAC systems.