Pre-filter:
- A pre-filter is the first line of defense in an AHU system. It is designed to capture larger particles such as dust, hair, and lint from the air.
- Pre-filters help extend the life of more expensive filters downstream by removing larger particles that can clog or damage them.
- Pre-filters generally have a lower efficiency compared to HEPA filters but are effective at capturing larger particles.
Bag filter:
- Bag filters are medium-efficiency filters that are designed to capture medium-sized particles like pollen, mold spores, and some dust.
- Bag filters typically have a higher efficiency than pre-filters but lower efficiency than HEPA filters.
- They are often made of synthetic fibers or a combination of synthetic and natural fibers arranged in a bag-like configuration.
HEPA filter (High-Efficiency Particulate Air filter):
- HEPA filters are the highest efficiency filters commonly used in AHUs. They are designed to capture very small particles, including bacteria, viruses, and other airborne contaminants.
- HEPA filters are capable of removing at least 99.97% of particles that are 0.3 microns in size.
- HEPA filters are crucial in environments where air quality and cleanliness are of utmost importance, such as hospitals, laboratories, and clean rooms.