1. Filtering efficiency: the fundamental distinction
This is the most fundamental and quantitative difference. The key lies in the filtration efficiency of specific particle sizes.
- High efficiency particulate air (HEPA) filter: For particles of 0.3 micrometers (μ m), the filtration efficiency is not less than 99.97%. This is the benchmark line for HEPA (H13 level).
- Ultra high efficiency filter (ULPA): For particles with a diameter of 0.1-0.2 microns (the most easily penetrable particle size, MPPS), the filtration efficiency is not less than 99.999%. Efficiency is 1-2 orders of magnitude higher than HEPA.
ULPA's efficiency has an additional 9 after the decimal point, but this means that the particle penetration rate has decreased by 10 to 100 times.
2. Testing standards and grading
The internationally recognized standards (such as EN 1822, IEST-RP-CC007.1) have clear classifications:
- HEPA filter classification (according to EN 1822):
- H13: Efficiency ≥ 99.95% for 0.3 μ m (often corresponding to 99.97%)
- H14: Efficiency ≥ 99.995% for 0.3 μ m
- ULPA filter classification (according to EN 1822):
- U15: MPPS efficiency ≥ 99.9995%
- U16: MPPS efficiency ≥ 99.99995%
- U17: MPPS efficiency ≥ 99.999995%
Distinguishing points: Look at the efficiency value and the corresponding test particle size. If the product information states "99.99% efficiency for 0.3 μ m", it is usually an H14 HEPA; If it is stated that the efficiency reaches 99.999% for 0.12 μ m, it is ULPA.
3. Application scenarios
Different efficiencies determine their application areas.
- HEPA filter: suitable for high cleanliness requirements, but not extreme scenarios.
- Typical applications: hospital operating rooms, general biological laboratories, pharmaceutical filling workshops, sterile food packaging, high-end household air purifiers, precision instrument manufacturing.
- Corresponding cleanroom grades: Core filters from ISO Class 5 (Class 100) to ISO Class 8 (Class 100000).
- ULPA filter: suitable for scenarios where particle control in the air reaches its limit.
- Typical applications: semiconductor chip manufacturing (integrated circuits, liquid crystal panels), nanotechnology research, highest level biosafety laboratories (P3, P4), aerospace precision component production, and some cutting-edge pharmaceutical research and development.
- Corresponding cleanroom grades: Core filters from ISO Class 3 (Level 1) to ISO Class 5 (Class 100).
4. Materials, Resistance, and Cost
- Filter material: Both usually use glass fiber filter paper, but ULPA fibers are finer, more densely arranged, or use more efficient filter membranes (such as ePTFE).
- Resistance (pressure drop): Under the same air volume, ULPA typically has an initial resistance that is 30% to more than twice that of HEPA due to its denser fibers. This means that stronger fans are needed and energy consumption is also higher.
- Cost: The manufacturing process of ULPA is more complex, with higher material requirements, and its price is usually twice or even several times that of HEPA of the same size.
