Which of the following is NOT a main component of an HVAC system?

The correct choice identifies filtration systems as not being a main component of an HVAC system in the context of the fundamental components that typically encompass the heating, cooling, and ventilation functions of the system.

HVAC systems are generally composed of three primary components: heating equipment, cooling equipment, and ventilation systems. Heating equipment is responsible for generating warmth during colder months, cooling equipment provides relief from heat during warmer months, and ventilation systems ensure a continuous supply of fresh air and proper airflow throughout a building.

While filtration systems play a crucial role in ensuring air quality by removing dust, allergens, and other particulates from the air, they are typically considered auxiliary to the main functional components of the HVAC system. Their primary purpose is not to control temperature or humidity directly, but rather to improve indoor air quality. Thus, while necessary for optimal performance, filtration systems do not represent a fundamental component that defines the HVAC system as heating, cooling, and ventilation do.