HEPA (High-Efficiency Particulate Air) filters are classified according to their filtration efficiency, which is determined by international standards such as EN 1822 and ISO 29463. Understanding these classifications is crucial for selecting the right filter for your specific application.

HEPA Filter Classification System

HEPA filters are categorized into different classes based on their efficiency at capturing particles of 0.3 microns in size:

• H10: 85% efficiency at MPPS (Most Penetrating Particle Size)
• H11: 95% efficiency at MPPS
• H12: 99.5% efficiency at MPPS
• H13: 99.95% efficiency at MPPS
• H14: 99.995% efficiency at MPPS

What is MPPS?

MPPS stands for Most Penetrating Particle Size, typically around 0.3 microns. This is the particle size that is most difficult to capture, making it the standard reference point for filter efficiency testing.

Choosing the Right HEPA Filter

The selection of HEPA filter class depends on several factors:

1. Cleanroom Classification: ISO Class 5-7 environments typically require H14 filters, while ISO Class 8 may use H13 or H12.
2. Application Requirements: Pharmaceutical and medical applications often mandate H14 filters for maximum protection.
3. Energy Efficiency: Higher efficiency filters have higher initial resistance, which can increase energy consumption.
4. Cost Considerations: H14 filters are more expensive but provide superior filtration performance.

Testing and Certification

All HEPA filters should be tested and certified according to recognized standards. Look for filters that come with individual test certificates showing efficiency, pressure drop, and airflow rate.

Maintenance and Replacement

Regular monitoring of pressure drop across the filter indicates when replacement is needed. Typically, HEPA filters should be replaced when the pressure drop reaches 2-3 times the initial value.