Heating & cooling elements: From cooling coils to heat exchanger coils, there are various elements inside an air handler unit. Different elements for heating and cooling may be incorporated based on the needs of the area. For instance, cold areas require frost coils. In contrast, areas with high humidity require a cooling coil with an over-cool feature so that condensation occurs when the dew point is reached.

Filters: Filters are an essential part of an air handler as they keep the air clean and free of dust. Several types of filters may be used, often in the same unit. It all depends on the specific needs of a space. Filters must be regularly cleaned and changed to continue to efficiently do their job.

Humidifier: A humidifier is added to units used in cool climates where the heater is frequently on. A humidifier adds moisture to prevent dry, static air. There are different humidifiers commonly used, from evaporative to spray mist.

Heat recovery device: This can reduce energy usage and increase overall capacity.

Controls: The controls are used to govern the mechanisms of a system, such as flow rate, air temperature, humidity, and air quality.

Vibration isolators: These are used to reduce the noise and vibrations created by the air handler to the rest of the building.