The fresh-air intake filter not only captures dust, dirt, and other airborne particles that can irritate the driver, it stops them from interfering with the performance of the heater and air conditioner. Without an effective filter, particles of dirt and dust can end up sticking on the evaporator core. As a result, the A/C system may not be able to absorb as much heat out of the cab as it would if the core were clean.
There are several different types of filters available:
- Paper: The most common type of fresh-air intake filters are made of pleated paper, the same type of media you’d find on the air filter in an engine. Dirt and debris settle into the folds and build up from there.
- HEPA: HEPA (High-Efficiency Particulate Air) filters are made of high-density pleated paper and capture extremely small particles that might be harmful to people with allergies or asthma.
- Foam: Some filters are made of open-cell foam and are charcoal-impregnated to help trap particles from cigarette smoke and neutralize the odor.
No matter what type of filter the vehicle has, follow the recommended inspection interval. In most cases, that means checking the filter every three months—at every oil change, for example—and using a replacement that meets the original-equipment spec.