UV-C kill is just dose. Enter the lamp output, the distance to the surface and how long it runs — we give you the delivered dose in mJ/cm² and the log reduction for the pathogen you care about, using D90 values from published 254 nm inactivation studies. No "kills 99.9% of germs" hand-waving.
Pick a fixture to load its rated UV-C output at 1 m, or enter your own. Surface dose only — air disinfection uses a different residence-time model.
Inverse-square law: irradiance falls with the square of distance from a point source. Dose = irradiance × time. Real fixtures are line/area sources, so close-up readings are conservative — confirm with a calibrated UV-C radiometer for validation work.
Inactivation is exponential in dose. Each D90 of dose removes one more log.
Irradiance@surface (µW/cm²) = Output@1m ÷ distance² Dose (mJ/cm²) = Irradiance × time(s) ÷ 1000 Log reduction = Dose ÷ D90 % inactivated = 100 × (1 − 10^−LogReduction)
D90 is the UV-C dose that inactivates 90% of a population — one log. Tougher organisms have higher D90: a vegetative virus like SARS-CoV-2 falls in ~1.6 mJ/cm², while C. difficile spores need ~20× that. The values here are mid-range figures from published 254 nm studies; real performance depends on humidity, shadowing and surface type.
This tool models a surface being irradiated at a fixed distance. Upper-room and in-duct UV-C disinfect moving air — there the relevant figure is the fluence delivered during each air pass, which depends on airflow and chamber geometry, not a single distance. For air-cleaning sizing use the room sizer; for UV-C-in-air systems, send us the room and we'll model the equivalent air changes.
Safety: direct 254 nm UV-C harms skin and eyes. Surface fixtures must run in unoccupied rooms with interlocks, or use shielded/upper-room geometry with occupancy controls. We supply the interlocks and commissioning — never operate an unguarded UV-C source in an occupied space.
Tell us the room, the target pathogen and the cycle time you can allow — we'll size the UV-C fixture, supply the interlocks, and price it in your currency with a 30-day trial.