HEPA Filter Complete Guide

HEPA stands for High Efficiency Particulate Air. It's a standard for air filters that must remove at least 99.97% of particles 0.3 microns in diameter according to the US DOE standard, or meet EN 1822 classifications in Europe.

H13 is the European EN 1822 classification requiring 99.95% efficiency at MPPS. "True HEPA" is the US marketing term for filters meeting the DOE standard of 99.97% at 0.3 microns. They're essentially equivalent, with H13 being slightly more stringent in testing requirements.

Yes, HEPA filters can capture viruses including SARS-CoV-2 (0.06-0.14 microns). While individual viruses are smaller than 0.3 microns, they typically travel on respiratory droplets that are larger. H13 HEPA filters capture 99.97% of particles at the most penetrating size, and efficiency is actually higher for both larger and smaller particles.

Replacement frequency depends on usage and air quality. General guidelines: Light use (8 hrs/day) in clean environments: 12-18 months. Moderate use (16 hrs/day) with pets or urban pollution: 8-12 months. Heavy use (24/7) in polluted areas: 6-8 months. During wildfire season or extreme pollution: 3-6 months. Always follow manufacturer recommendations and monitor filter condition.

Most HEPA filters cannot be washed or cleaned effectively. Water damages the delicate fiber structure and permanently reduces efficiency. Only filters specifically marked as "washable HEPA" can be cleaned, and even these have limited washing cycles. Vacuuming may remove surface dust but won't restore filter efficiency. For optimal performance, replace filters as recommended.

H13 (99.95-99.97%) is better than H12 (99.5%) in terms of filtration efficiency, but the difference may not be noticeable for everyone. H13 is recommended for severe allergies, asthma, or immunocompromised individuals. H12 offers excellent filtration for most homes at a lower cost and with less pressure drop (meaning quieter operation and lower energy use). Consider your specific health needs and budget.

No, HEPA filters only capture particles, not gases or odors. For odor and gas removal, you need activated carbon filters or other adsorbent materials. Many air purifiers combine HEPA filters with activated carbon layers to address both particles and odors. VOCs, smoke odors, cooking smells, and chemical fumes require carbon or specialized gas-phase filtration.

MPPS stands for Most Penetrating Particle Size, typically around 0.3 microns for HEPA filters. This is the particle size that's hardest to capture because it falls between the effective ranges of different filtration mechanisms. Larger particles are caught by impaction and interception, smaller ones by diffusion. Testing at MPPS ensures the filter performs well across all particle sizes—if it captures 99.97% at MPPS, it captures even more above and below this size.

For most homes, H14 (99.995%) is overkill. The marginal improvement over H13 (99.97%) is negligible in residential settings. H14 filters have higher pressure drop, requiring more powerful (noisier) fans and consuming more energy. They're also significantly more expensive. H14 is justified for medical facilities, cleanrooms, or individuals with extreme health conditions. For typical home use, even with allergies, H13 provides excellent protection.

Look for: 1) Specific efficiency rating (99.97% at 0.3 microns or EN 1822 grade), 2) Individual test certificate or serial number, 3) Certification from recognized bodies (EN 1822, ISO 29463), 4) Clear labeling as H13 or "True HEPA" (not "HEPA-type" or "HEPA-like"), 5) Reputable manufacturer with verifiable testing data. Be skeptical of vague claims like "99% HEPA" or missing specifications.