HEPA vs ULPA: The Short Answer
HEPA and ULPA are both high-efficiency air filters classified under EN 1822 at the Most Penetrating Particle Size (MPPS). The difference is the guaranteed minimum efficiency: HEPA (H13–H14) captures 99.95%–99.995% of MPPS particles, while ULPA (U15–U17) captures 99.9995%–99.999995%. In practice ULPA lets 10 to 1,000 times fewer particles through, but at a higher pressure drop and cost. The rule for a technical buyer is simple: choose the lowest class that meets your cleanliness target, not the highest available.
Efficiency and Penetration Compared
Both families are tested at the MPPS (typically 0.1–0.25 µm), the particle size a filter captures least efficiently, so the rated value is a guaranteed minimum. The table shows how quickly penetration falls as the class rises.
| Class | Standard | Min. efficiency at MPPS | Max. penetration |
|---|---|---|---|
| H13 | EN 1822 | 99.95% | 0.05% |
| H14 | EN 1822 | 99.995% | 0.005% |
| U15 | EN 1822 | 99.9995% | 0.0005% |
| U16 | EN 1822 | 99.99995% | 0.00005% |
| U17 | EN 1822 | 99.999995% | 0.000005% |
When HEPA Is Enough
For the large majority of contamination-controlled projects, an H13 or H14 HEPA filter meets the required ISO 14644-1 cleanliness class:
- Pharmaceutical cleanrooms (typically ISO 5–8)
- Hospitals, operating theatres and isolation rooms
- Laboratories and research facilities
- Food and beverage production
- Terminal filtration in HVAC systems
Explore Safe Air HEPA filters or the range for cleanroom applications.
When ULPA Is Worth It
ULPA is justified only where even HEPA penetration is too high, usually in ISO 14644-1 Class 1–4 environments:
- Semiconductor and microelectronics fabrication
- Nanotechnology and precision optics
- Aerospace components
These overlap with electronics and optics manufacturing. Because ULPA media is denser, confirm the fan can hold the design airflow at the higher resistance.
Common Selection Mistakes
- Specifying ULPA where an H14 filter already satisfies the risk assessment, paying more in energy for no benefit.
- Comparing filters only by class or outer size, ignoring the efficiency test method, airflow and pressure drop.
- Forgetting that efficiency is defined at the MPPS, per EN 1822.
Get the Right Class for Your Project
Define your target ISO class, airflow and pressure limit first, then choose the lowest filter class that reliably meets them. As a Turkey-based manufacturer, Safe Air produces H13, H14 and ULPA-class filters in standard and custom sizes. Send your dimensions, filter class and airflow for a project-specific quotation.
Frequently Asked Questions
Both are classified under EN 1822 at the most penetrating particle size (MPPS). ULPA filters reach a higher minimum efficiency (U15–U17, from 99.9995%) than HEPA filters (H13–H14, from 99.95%), but at a higher pressure drop.
No. ULPA offers higher efficiency but also higher resistance, energy use and cost. The correct choice depends on the required ISO cleanliness class, airflow and fan capacity, not on the highest available class.
Under EN 1822, HEPA covers classes H13 and H14, while ULPA covers U15, U16 and U17. E10 to E12 are classified as EPA filters, below HEPA.
Often yes. ULPA media is denser and typically has a higher initial pressure drop, so the system must have enough fan capacity to maintain the design airflow. This should be verified before replacing HEPA with ULPA.
Only after a technical assessment. Even with matching external dimensions, airflow, pressure drop, sealing and validation requirements may differ, and the change can affect system performance and compliance.
ULPA is common in semiconductor and microelectronics fabrication, nanotechnology, optics and the most demanding ISO Class 1–4 cleanrooms. Most pharmaceutical, hospital and HVAC applications are met by H13 or H14 HEPA filters.
