UV Wavelengths in 30 Seconds
- UV-C (200–280nm): Germicidal — disinfection & sterilization
- UV-B (280–315nm): Phototherapy & weathering tests
- UV-A (315–400nm): Curing, printing, lithography
- Wavelength determines application — not just "UV"
The UV Spectrum
Practical Guide
Which Wavelength Do I Need?
Disinfection: 254nm (mercury) or 265nm (LED). Curing: 365–405nm depending on photoinitiator. Water treatment: 254nm standard, 222nm emerging.
Why 265nm for Germicidal?
Peak DNA absorption is at ~265nm, not 254nm. Mercury lamps emit at 254nm because that's their physics — but 265nm LEDs are actually closer to the biological optimum.
Photoinitiator Matching
UV curing efficiency drops >50% if the LED wavelength is 20nm off the photoinitiator's absorption peak. Always match your light source to your chemistry.
Safety by Wavelength
Shorter wavelength = higher energy per photon but shallower penetration. Far-UVC (222nm) can't reach living skin cells. 254nm can cause burns and eye damage without PPE.
LED Efficiency by Band
UV-A LEDs (365–405nm): 40–60% WPE. UV-B LEDs: 5–15% WPE. UV-C LEDs (265nm): 3–10% WPE. Efficiency improves at longer wavelengths.
Next Step
Use our UV Simulator to model different wavelengths and see how they affect dose distribution in your specific geometry.
DNA absorption peaks at 265nm — the sweet spot for UV-C LEDs. Mercury lamps emit at 254nm, which is still highly effective but 10nm away from the true optimum.
Wavelengths & Applications
| Wavelength | Band | Source | Applications | Key Fact |
|---|---|---|---|---|
| 222nm | Far-UVC | KrCl Excimer | Occupied-room disinfection, Hospital air treatment | Safe for continuous human exposure — cannot penetrate living tissue |
| 254nm | UVC | Low-pressure Mercury | Water treatment, Surface disinfection, Air purification | Industry standard for 70+ years. Banned after 2027 (Minamata Convention) |
| 265nm | UVC | AlGaN LED | Point-of-use water, Compact disinfection, Medical devices | Peak DNA absorption — the biological optimum for germicidal effect |
| 275–285nm | UVC | AlGaN LED | Water disinfection, Sensor sterilization | Higher LED efficiency than 265nm, still effective germicidal range |
| 310–313nm | UVB | Narrowband UVB lamp / LED | Psoriasis phototherapy, Vitiligo treatment | Medical standard for skin phototherapy since the 1980s |
| 365nm | UVA | LED / Mercury | Industrial coatings, 3D print resins, Medical adhesives | Matches classic photoinitiators. LED output: up to 12 W/cm² |
| 385nm | UVA | LED | Inkjet printing, Mixed production lines | Best compromise between surface cure and depth cure |
| 395nm | UVA | LED | Printing inks (inkjet, flexo, offset), Adhesives | Industry standard — 50–60% market share. Highest LED efficiency, lowest cost/W |
| 405nm | UVA/Visible | LED | Dental composites, Furniture/auto coatings, Cationic epoxies | Best depth penetration. Longest UV wavelength, lowest photon energy |
At 222nm, photons cannot penetrate past the dead skin layer (stratum corneum) or the eye's tear film. This makes continuous room disinfection possible while people are present. ACGIH TLV at 222nm is 27× higher than at 254nm.[7]
A 395nm LED will not disinfect (it's UV-A, not UV-C). A 254nm lamp will not cure most UV inks (wrong band). Always verify that your light source matches your application's wavelength requirements.
Need Expert Guidance?
Our team helps you select the right UV technology for your application — vendor-neutral, data-driven.
- [6] Bolton & Linden (2003): Standardization of Methods for Fluence UV Dose
- [7] Welch et al.: 66-Week Far-UVC Skin Safety Study; Sugihara et al.: 36-Month Eye Study
- [9] IEC 62471: Photobiological Safety of Lamps and Lamp Systems