The filtered-excimer sources behind far-UVC, the categories of fixtures on the market, the spec terms that actually matter, and the questions to ask before you buy — described factually, without inventing brand claims.
Nearly all commercial 222 nm products use a krypton-chloride (KrCl) excimer lamp. An excimer (“excited dimer”) source runs an electrical discharge through a gas mixture that emits a narrow band of UV when the excited molecules break apart — for KrCl, centered near 222 nm. On its own, a KrCl lamp also emits a small tail of longer, skin-penetrating wavelengths, so far-UVC fixtures place an optical band-pass filter in front of the lamp to remove that tail. The phrase you will see — filtered excimer — is the whole safety story in two words. An unfiltered KrCl lamp is not safe far-UVC.
“Care222” is a well-known example of this approach: it is Ushio’s filtered 222 nm module, developed with technology out of the far-UVC research community, and it is supplied to a number of fixture makers who build finished products around it. When a product lists a Care222 module, it is signaling a filtered excimer source rather than a raw lamp.
Mounted units that illuminate an occupied room continuously within exposure limits. Coverage depends on ceiling height and mounting geometry, so these are typically specified per room rather than bought by the unit.
Fixtures that concentrate output into a defined zone. Related to classic upper-room UVGI thinking, they are useful where a designer wants disinfection focused away from close-range occupancy.
Smaller plug-in units for a single desk or small space. Convenient, but coverage and delivered dose are correspondingly limited — useful as a supplement, not a whole-building strategy.
Real players include Ushio (Care222, Japan), Far UV Technologies (KrCl fixtures, United States), and Eden Park Illumination (Champaign, Illinois; next-generation far-UVC sources). Fixture builders integrate these modules into finished products.
Cutting through marketing means reading a few numbers correctly:
Far-UVC is not only a purchase price; it is a system with running costs. The excimer module has a rated lifetime measured in operating hours and degrades gradually, so a fixture that met its dose target when new must be maintained and eventually re-lamped to keep delivering the same protection. Ask makers for the rated hours, the replacement-module cost, and whether the fixture monitors or estimates output over its life. Electricity is generally modest, but the real total cost of ownership is dominated by module replacement and by the up-front engineering and commissioning described on the applications page. Because coverage depends on room geometry, whole-room fixtures are sensibly specified per room rather than bought by the unit — a single number of “square feet covered” on a box is a red flag unless it states the mounting height and the resulting occupied-zone irradiance.
A trustworthy datasheet lets you reconstruct the safety and efficacy story yourself: a filtered spectrum centered at 222 nm, an irradiance figure with the distance it was measured at, a stated germicidal dose over time against named pathogens, the occupied-zone exposure and the run time that keeps it within ACGIH / ICNIRP limits, independent ozone data, an IEC 62471 test result with risk group, and rated lamp life. A datasheet that offers a bold “kills 99.9% of germs” headline but none of those numbers is marketing, not evidence — and far-UVC is a field where the numbers are exactly what separate a safe, effective fixture from a hazard.
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