HVAC UV-C vs. HEPA

HEPA stands for High-Efficiency Particulate Air filter. The technical definition lives in EN 1822-1 (Europe) and ISO 29463 (international): a filter must capture at least 99.95% of particles at the Most Penetrating Particle Size (MPPS) to be class H13. H14 raises the bar to 99.995%, U15–U17 (ULPA) goes further still.

In practice, the word "HEPA" gets used very loosely. Many consumer and small-commercial products labeled "HEPA-grade", "HEPA-style", or "True HEPA" carry no EN 1822 / ISO 29463 certification at all — those are manufacturer marketing labels, not norm-tested classifications. There is no global authority that polices the term itself.

Engineer takeaway: for hygiene-critical specifications (hospital supply air, cleanroom, pharma fill-finish), always require an explicit class — "EN 1822 H13" or "EN 1822 H14" with current test certificate — not just "HEPA". Without the class number, you do not have a guaranteed minimum efficiency, and the conversation in this page (where to swap H13/H14 for H9 + UV-C) only applies to the certified case.

Three norms govern HVAC filter classification. Each labels the same physical reality differently — knowing which standard a datasheet number refers to is half the spec battle.

EN 1822 — HEPA + ULPA filters (efficiency at MPPS, the hardest particle size to catch):

• E10–E12 — "EPA" (Efficient Particulate Air), 85–99.5%
• H13 — ≥ 99.95%, entry-level HEPA, hospital supply, pharma grade C/D
• H14 — ≥ 99.995%, fill-finish, cleanroom ISO 5+
• U15–U17 — ULPA, 99.9995% to 99.999995%, semiconductor / biotech

EN ISO 16890 — current standard for general ventilation (since 2018, replaces EN 779). Efficiency is reported per particle-size band:

• Coarse — large particles only (pollen, hair, lint), pre-filter stage
• ePM10 — ≥ 50% capture in PM10 band, typical office supply
• ePM2.5 — ≥ 50% in PM2.5, allergens, fine dust
• ePM1 — ≥ 50% in PM1 (bacteria, soot, combustion particles): the "fine filter" range that pairs with UV-C disinfection

EN 779 — replaced by ISO 16890 in 2018, but still seen in older datasheets:

• G1–G4 — coarse, roughly today's Coarse / ePM10
• M5–M6 — medium, ≈ ePM10 50–60%
• F7 ≈ ePM1 50%
• F8 ≈ ePM1 70%
• F9 ≈ ePM1 80%

And "H9"? "H9" is HVAC industry shorthand that does not exist in EN 1822 — that standard starts at H13. What spec sheets and field installers call "H9" is in current EN ISO 16890 terms an ePM1 ≈ 60–80% filter, formerly F9 under EN 779. It sits at the upper end of "fine filter" right before HEPA territory begins — exactly the right pre-filter to pair with UV-C: it captures dust and large bioaerosols, and UV-C handles the small viruses that would otherwise need H13 to be sieved out mechanically.

Need help reading a filter datasheet? Send it via /contact — we map old EN 779 numbers to current ePM classes and tell you whether a "HEPA-style" claim has an EN 1822 certificate behind it. Vendor-neutral, no purchase required.

Filter pressure drop scales fan power roughly linearly: 100 Pa extra pressure on a 10,000 m³/h supply costs about 0.28 kW of continuous fan input (assuming ~70% fan efficiency). Across 8,760 h/yr that is ~2,450 kWh — at €0.30/kWh, that is €735 per year, per 100 Pa, per 10,000 m³/h.

A H13 stage at 350 Pa average pressure-drop costs roughly €2,500/yr in fan energy on that geometry. An ePM1 + UV-C combo at ~150 Pa average costs roughly €1,100/yr. Multiply by 5 years and you usually exceed the entire capex difference.

Yes, but the dose has to be sized for the residence time. A SARS-CoV-2-like coronavirus reaches 99% inactivation at roughly 2–5 mJ/cm² (UV-C 254 nm). At 2 m/s duct velocity with a 1 m UV-C section, residence time is 0.5 s — so the lamp must deliver 4–10 mW/cm² average across the cross-section to hit that dose.

This is exactly the parameter the simulator computes: lamp count, position, and reflective duct walls drive the average fluence. ASHRAE 185.1 [14] is the standard test method for this.

Three scenarios where you should keep HEPA and not propose this swap:

• Cleanrooms (ISO 14644 class 5 or stricter): particle count limits are non-negotiable, and they require physical capture.
• Hazardous aerosols / BSL-3/4: the hazard is the particle itself (toxin, spore, prion), not just biological viability. Inactivation does not equal capture.
• Pharma fill-finish, sterile manufacturing: regulatory expectation is HEPA. UV-C is supplementary, not a replacement.

The simulator's HVAC-duct application (open it here) already encodes this trade-off in its lamp-guidance reasoning. Enter your duct geometry, target pathogen, and airflow — the tool returns recommended lamp count, dose distribution, and a pass/fail on the chosen target.

That output is the technical proof you need to put in front of a facility engineer alongside the H13 spec they originally received.

Two installation modes, both supported by the simulator with different log-reduction targets:

• Duct-internal lamps (hvac-kanal-extern in the simulator, ASHRAE 241, 1-log target): lamps inserted through the duct wall, fastest retrofit, smallest footprint. Best for offices, schools, light-industry HVAC where 90% reduction is the spec target. Caveat: dose peaks around the lamp, outer flow paths are weaker — Amalgam lamps compensate in narrow ducts.
• Separate UV-chamber (hvac-uv-kammer, VDI 6022 / GMP grade C/D, 2-log target): inline chamber module between duct segments, reflective inner walls (anodized aluminum or PTFE) deliver +30–60% dose at the same lamp wattage. Required for hospital supply air, pharma fill-finish areas, food-processing supply where 99% reduction is mandated. Adds ~50–150 Pa flange pressure-drop — check the fan reserve.

Pre-select the variant in the simulator before sizing — the lamp count and required power scale very differently.