UV Lamp Technologies — Overview

A reference to the lamp technologies that appear in the simulator as recommendedLampGuidance.preferredTypes. Continuously extended with field experience.

Matrix — Which Technology When

Low-Pressure Hg (254 nm)

• Mechanism: low-pressure mercury-vapour discharge. The emission is effectively monochromatic, concentrated at the 254 nm (253.7 nm) mercury resonance line.
• Efficiency: roughly 35–40 % wall-plug efficiency under optimised cold-spot temperature and operating current — the highest of the common UV-C source technologies. Optimum radiant yield occurs at a cold-spot temperature of roughly 40–50 °C.
• Form factor: long tubes (similar to fluorescent tubes), often 60–150 cm.
• Cooling: passive (air) or active (water, for immersion sleeves).
• Maintenance: lamp replacement after roughly 8,000–12,000 h of typical service life; quartz-sleeve cleaning depending on water quality.
• Use cases: HVAC air ducts, drinking water (DVGW-certified systems), cooling-tower bypass and basin treatment.

Amalgam (High-Output Hg, 254 nm)

• A variant of the low-pressure lamp using a solid mercury-amalgam depot instead of free liquid mercury.
• The amalgam spots act as a vapour-pressure regulator, absorbing and releasing mercury as lamp conditions fluctuate, which keeps UV output stable across a wide ambient-temperature range (effective up to high surrounding temperatures of roughly 90 °C).
• This stability allows much higher loading: amalgam lamps deliver up to roughly 10× the UV power density of a conventional low-pressure mercury lamp.
• Advantage: fewer lamps per system at high throughput, hence fewer points of failure.
• Disadvantage: higher cost than standard low-pressure lamps.
• Service life: coated long-life amalgam lamps can reach up to ~16,000 h while still retaining a high share (~80–90 %) of their initial UV-C output.

Medium-Pressure Hg (Broadband 200–400 nm)

• A higher mercury vapour pressure broadens the emission into a polychromatic spectrum spanning UV-C, UV-B and UV-A (roughly 200–400 nm) at high intensity.
• Individual lamps reach several kilowatts of electrical power.
• Advantage: broadband UV can act on deeper water layers and on biofilm substrate; high power per lamp keeps lamp count low.
• Disadvantage: substantially lower efficiency (on the order of 15–20 %), high heat load, and shorter service life than low-pressure lamps.
• Use cases: UV curing (UV-A/B/C for complex coatings), cooling towers with poor water quality, ballast-water disinfection.

UV-C LEDs 265–280 nm

• Semiconductor-based UV-C generation using aluminium-gallium-nitride (AlGaN); under forward bias, injected electrons recombine with holes and release UV photons.
• Strengths: long potential service life, no mercury, instant on/off, selectable peak wavelength.
• Weaknesses (2025/2026): low power per chip and still-modest wall-plug efficiency. State-of-the-art commercial devices reach roughly 10 % wall-plug efficiency at ~200 mW and 265 nm, with rated lifetimes exceeding 20,000 h; volume production of the ~200 mW class is expected toward the end of 2026. Thermal management remains critical.
• Use today: point-of-entry (POE) drinking water for households, small spot applications, laboratory use.
• Outlook: efficiency and per-device power are improving; broader adoption beyond point-of-use systems depends on those gains continuing.

UV-A LEDs 365–405 nm (for Curing)

• A mature, well-established technology for UV curing.
• High-power modules are available; modern 385/395 nm devices commonly deliver irradiance levels exceeding 15–25 W/cm² in flood configurations, and considerably more in focused spot systems.
• Wavelength is chosen to match the curing chemistry: 365 / 385 / 395 / 405 nm. 365 nm favours deeper penetration and legacy chemistries; 395 nm is the mainstream choice for many modern inks and high-speed lines.
• Runs cool relative to mercury arc lamps, limiting heat input to the substrate.
• Use cases: conveyor-belt curing, spot bonding, digital printing.

Excimer KrCl (222 nm, Far-UV-C)

• Krypton-chloride excimer lamp with a sharp emission peak near 222 nm.
• Key property: at wavelengths below ~230 nm the radiation is strongly absorbed by the outer skin (stratum corneum) and the tear film, so it reaches living cells far less than 254 nm radiation does.
• Safety thresholds are under active revision: the ACGIH Notice of Intended Change places the proposed skin TLV at 222 nm in the range of roughly 150–500 mJ/cm² (substantially above the long-standing 25 mJ/cm² UV-C limit). Optical filtering is essential — unfiltered KrCl lamps emit longer-wavelength components that are not skin-safe.
• Use cases: occupied-space ("people-present") room disinfection, specialised pathogen inactivation.
• Disadvantages: shorter service life, higher cost, and less UV output per unit than mercury lamps.

Excimer Xe (172 nm)

• A specialised technology for surface activation: cleaning and modifying substrate surfaces at the molecular level prior to coating, and sterilising plastic surfaces.
• The 172 nm photon energy (~7.2 eV) is high enough to break the main bonds of organic molecules directly.
• The penetration depth at 172 nm is extremely short — on the order of hundredths of a millimetre — so the technology is not suited to flow-through water or room disinfection, only to surface treatment.

Decision Logic per Application

• HVAC / room air: low-pressure 254 nm (standard); KrCl 222 nm for occupied rooms.
• Drinking water, household (POE): UV-C LED 265–280 nm (low maintenance, compact) or low-pressure Hg.
• Drinking water, municipal: DVGW-certified low-pressure Hg; amalgam for high flow rates.
• Cooling-tower basins: low-pressure Hg (IP68, submerged); amalgam for large basins; medium-pressure only where turbidity demands broadband UV.
• Process water, inline: low-pressure Hg in a pipe reactor; amalgam at high throughput.
• Conveyor-belt food: low-pressure Hg with shatter protection (FEP sleeve); amalgam for wide belts.
• Conveyor-belt curing: UV-A LED 365–405 nm (preferred); medium-pressure Hg for complex multi-component coatings.
• Spot curing: UV-A LED with spot optics (focused); mercury point sources for special cases.
• Evaporator, internal: UV-C LED or low-pressure lamp with a reflector channel.
• Evaporator, external: low-pressure 254 nm; radiation shielding mandatory.

Where This Feeds In

• recommendedLampGuidance.preferredTypes in each templates/*.ts.
• TODO: review every app-template lamp recommendation together with the user.
• TODO: a website comparison table — "Which lamp technology for my application?" — as a lead magnet.

Cross-References

• Wavelengths and Action Spectra — which wavelength is biologically effective.
• UV Lamp Anatomy — quartz envelopes, electrodes, fill gas, cooling.
• Ballasts and Drivers — driver electronics and placement.
• LED Area Emitters — UV-LED arrays for uniform area irradiation: construction, anatomy, wavelength options, application matrix.
• UV-LED Lifetime and Degradation — L70 modelling, thermal ageing, AlGaN degradation, UV-A vs UV-C asymmetry, maintenance thresholds.

Sources

This article draws on peer-reviewed literature, manufacturer documentation and the IUVA UV Disinfection Handbook. Manufacturers are named only as class examples, never as recommendations.

• IUVA UV Disinfection Handbook (Bolton & Cotton) — general UV-source reference.
• Peer-reviewed efficiency, ageing and safety studies (ResearchGate, NIH/PMC, Wiley, AIP, CORM) for low-pressure, medium-pressure, amalgam, UV-C LED and KrCl excimer characteristics.
• Manufacturer documentation (e.g. Heraeus Noblelight, LightSources, American Ultraviolet) for amalgam and low-pressure lamp specifications.

See the linked source records for the full citation list.