Customer Problem
Are your Air Handling Unit (AHU) operating costs skyrocketing while air quality downstream continues to deteriorate? Facilities management teams often notice rapid airflow reduction, high energy bills, and premature system cleanings. Selecting the wrong combination of air filters for an AHU system leads to unbalanced static pressure, frequent equipment downtime, and inadequate indoor air quality (IAQ) compliance.
Cause & Principle
Air filtration in an AHU works on the principle of gradient particle separation. Air contains particles ranging from visible dust (>10 μm) to microscopic airborne viruses (<0.3 μm). Attempting to catch all contaminants with a single, high-efficiency filter causes immediate surface loading, triggering an exponential rise in fan resistance. According to fan affinity laws, every additional 100 Pa of differential pressure forces the supply fan to consume significantly more kilowatt-hours to maintain designed CFM.
Comparison of Filter Stages
| Filter Class | Typical Efficiency | Primary Role | Common Form Factor |
|---|---|---|---|
| Primary (G1–G4 / Coarse) | Traps particles >10 μm (pollen, lint, hair) | Protects heating/cooling coils and secondary filters | Synthetic panel, pleated filter, air filter roll |
| Secondary (M5–F9 / ePM10, ePM1) | Traps 1–10 μm fine dust, smoke, mold spores | Protects ductwork, indoor occupants, and HEPA filters | Pocket / bag filter, rigid cell filter |
| Final / HEPA (H10–H14) | Traps down to 0.3 μm at 99.97%+ efficiency | Delivers ultra-clean air for sensitive environments | Mini-pleat, deep-pleat HEPA box filter |
How to Select
To build an optimal multi-stage configuration, match your facility’s requirements:
- Standard Commercial Buildings (Offices, Malls): 2-Stage System → G4 Panel Filter (Pre-filter) + F7 Pocket Filter (Secondary).
- Industrial & Food Processing: 2 or 3-Stage System → G4 Pleated Filter + F8 Bag Filter + Optional Activated Carbon Stage (for odor/VOCs).
- Pharmaceutical & Semiconductor Cleanrooms: 3-Stage System → G4 Panel + F9 Rigid Cell Filter + H13/H14 HEPA Filter.
Common Mistakes
- Skipping the Pre-Filter: Installing an F7 or HEPA filter without a G4 pre-filter ruins the expensive fine filter within weeks.
- Ignoring Total Cost of Ownership (TCO): Buying cheap filters with high initial resistance costs 3x to 5x more in electricity over the filter’s lifespan than investing in low-resistance media.
- Changing Filters Only on a Fixed Calendar: Replacing filters on a rigid 6-month schedule instead of monitoring actual pressure differential (ΔP) leads to either wasted lifespan or severe fan overload.
The Airy Solution
Guangzhou Airy Filter Media Co., Ltd. manufactures low-resistance, high-dust-holding capacity media tailored for international AHU specifications:
- Airy Progressive Density Media: Multi-layer synthetic structure that captures dust through the entire depth of the filter, lowering initial pressure drop by 15–20%.
- Full-Range Matchability: From G1-G4 washables and roll media to F7-F9 ultrasonic pocket filters and H13 HEPA units, Airy provides a fully compatible one-stop supply chain.
Frequently Asked Questions
How do I know when my AHU filters need replacement?
Always monitor the differential pressure gauge (e.g., Magnehelic). Replace primary filters when initial pressure doubles, or when secondary filters reach their recommended final resistance (typically 250 Pa for bag filters).
Can Airy manufacture custom sizes for non-standard AHUs?
Yes. Airy custom-cuts and fabricates metal frame panels, bag depths, and header dimensions to match OEM AHU tracks.
