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Central ventilation (AHU)

Retrofit UV-C into a central ventilation system

disinfection ✓ Confidence high (textbook/standard) HVACPharmaClinicOffice buildings DuctCentral Norm compliancePersonnel healthNo chemicals
How it works

Microbiological effect

Wavelength254 nm
D-value (1-log)8 mJ/cm²
Log reduction (typ.)1-log
Contact time0.3 s
Human safety ⚠ NOT skin-safe — worker protection required
Target pathogens Influenza AAspergillus nigerBacillus subtilis sporesSARS-CoV-2MS2 Coliphage

01 Why UV-C here?

UV-C disinfection inside the central ventilation system / AHU chamber. For industrial and large-commercial scale (office buildings, large hotels, clinics, pharma administration). Larger units are usually walk-in — wherever we mount lamps, a person has room to work. For very large plants >100k m³/h, several rooftop chambers with their own access points are typical, each UV-equipped on its own.

For classrooms, waiting areas or small rooms, standalone room-air units are the right choice (see "UV ceiling recirculation unit" or "UV wall luminaire").

03 Where is it used?

Use cases Office buildingsLarge hotelsHospitals (central)Industrial administration
Audience Office buildings / administration with central HVACLarge hotels with central ventilationClinics / large hospitals, central supply airIndustrial administration / corporate sites

05 Standards

ASHRAE 241DIN EN 16798-3

Installation notes

  • Filters made of UV-C-resistant material (fiberglass) — standard PE/PP filters disintegrate under continuous UV within months
  • Route cables outside the direct UV radiation, or use UV-C-resistant cabling — standard PVC becomes brittle
  • Seal the bores against draft with an EPDM grommet (otherwise leak air + condensation)
  • Mount ballasts/drivers outside the airstream (condensation protection for the electronics)
  • Walk-in ducts: an interlock on the inspection access is mandatory — UV-C harms eyes and skin within seconds

⚠ Worker-safety notes

  • UV-C safety goggles EN 170 / EN 207 (UV400+) mandatory during lamp maintenance
  • ICNIRP TLV at 254 nm: 6 mJ/cm² for 8 h exposure (unprotected)
  • OStrV § 5 + TRGS 530 — a documented risk assessment is mandatory
  • Access the UV-irradiated area only with the lamp switched off (mechanical interlock)
  • DGUV Information 209-085 (UV radiation in the workplace) as the training basis

Scientific references

  1. Ultraviolet Germicidal Irradiation Handbook: UVGI for Air and Surface Disinfection
    Kowalski W. · 2009 · Springer · book
  2. ASHRAE Standard 185.1-2020: Method of Testing UV-C Lights for Inactivation of Microorganisms in Forced-Air HVAC Equipment
    · 2020 · standard
  3. ASHRAE Standard 241-2023: Control of Infectious Aerosols
    · 2023 · standard

Engineering recommendation — lamp choice rationale

MercuryAmalgam

External-to-duct installation is the retrofit standard: lamps are fed into the airstream through bores in the duct wall and powered externally. Advantages: no separate chamber needed, maintenance without interrupting the airflow (with correct interlocks). Disadvantages: the UV zone is limited to the duct cross-section, and the dose peak sits right around the lamp — outer air paths receive weaker irradiation. Amalgam lamps compensate with higher output density; for ducts under 40 × 40 cm cross-section, amalgam emitters are often the only practical choice.

Note — **retrofit reality:** this variant is by far the most common on the market. When a customer says "UV in HVAC" and isn't planning new construction, they mean this variant 90 % of the time.

Plan your project with this

Discussion — Central ventilation (AHU)

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