Ozone Generation by Ultraviolet Lamps

Ozone generation by Krypton–Chloride (KrCl) 222-nm lamps

Krypton–Chloride (KrCl) lamps are a special form of excimer lamps. These lamps are filled with a mixture of Krypton and a very small percentage of Chlorine and emit mainly at 222 nm. This kind of lamp is seeing rapidly growing applications in disinfection applications, especially in occupied spaces. Figure 3 provides the spectral emission of a KrCl 222 nm lamp (notice the semi-log graph).

Comparing this typical spectrum of an unfiltered KrCl lamp with the oxygen absorption of Fig. 1, one will find that there is an insignificant, but detectable amount of radiation below 200 nm that can produce ozone. That means that there is a potential that ozone can be generated by this kind of lamp. However, the contribution of the main 222-nm wavelength to the ozone generation is usually negligible.

It should be noted that the spectrum is inherent to all KrCl discharge lamps, so it typically does not depend on the manufacturer, lamp design or the applied technology. Some manufacturers have developed sophisticated filter technology to not only suppress radiation above 230 nm but also apply filter technology to reduce wavelengths below 200 nm and therefore further reduce ozone generation.

It also must be noted that the total amount of ozone generation will depend on the total amount of emitted optical radiation (the radiant power in Watts). Therefore, a high-power lamp (e.g. 300 W electrical) will create proportionally much more ozone than a 12-W lamp. In addition, the actual operational duration (“run time”) of a lamp (typically within 8 h) in the application has to be considered in any assessment of ozone generation.

Examples of ozone generation by commercial KrCl 222 nm lamps

12-W lamp. The measured ozone generation of an Ushio Care222 B1, 12-W filtered 222-nm module is 0.012 mg h−1. This module encloses 4 KrCl lamps into an (almost) airtight housing and contains a quartz window with filter. By calculating a “standard room” size of 3 × 4 × 2.5 m = 30 m3, it will take 267 h to fill that room to 0.05 ppm. Or, within 24 h (constantly running the lamp) one would fill the room to 0.0045 ppm (4.5 ppb). That amount would not be smelled and is well below any FDA limits.

This would be the maximum amount to be expected. In reality, the lamp will likely not run more than 1 h per day (some time in occupied, some time in nonoccupied room). For a 1 h run time, the ozone concentration would be 0.2 ppb. Obviously, if multiple modules were installed in one room, these concentrations will have to added, and if the room size changes the concentration will be different. Nonetheless, the above calculations show that under no circumstance an ozone level of 50 ppb can be reached in any practical installation with these modules.


Ozone concentration in occupied spaces is an important design consideration when using UV-C emitting lamps. Ozone–free low-pressure mercury lamps, manufactured with an appropriate envelope material cannot produce ozone. Since there are ozone producing quartz lamps in the marketplace, that are similar in power and design to ozone-free quartz lamps, users must pay special attention to the manufacturers specification and avoid the accidental use of ozone-generating lamps under all circumstances in nonspecified applications.

Depending on design, power and operation time, KrCl 222 nm lamps can be responsible for the generation of ozone in air. This has to be taken into account and measured when designing fixtures with KrCl lamps. However, low-power (<15W) 222 nm lamps and modules are not expected to generate any significant ozone amounts that would lead to—or even approach—the recommended (and legal) limits for ozone concentrations in rooms.

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Currently, the most effective and safest way to fight against COVID-19 is far uvc 222nm technology, but experts warned that some of the products are not certified.

A key advantage of the UV-based approach is that UV light is likely to be effective against all airborne microorganisms, in marked contrast to vaccination methods. For example, while the inactivation efficiency of UV light will almost certainly vary as different strains of influenza virus emerge, they are unlikely to be significant. Similarly, as multidrug-resistant variants of bacteria emerge, their UV inactivation capacity is unlikely to vary greatly.

Care222 is a new disinfecting light source that, even though not harmful to the skin or eyes of humans or animals, deactivates bacteria and viruses in the same manner as conventional ultraviolet sanitizers.

It can be installed in a high location, such as on the ceiling, to irradiate its entire surroundings. This makes it possible to deactivate or eliminate a wide variety of viruses and bacteria both in the air and on environmental surfaces.

Care222 uses an excimer lamp (a mercury-free UV excimer light source produced by Ushio especially for outputting monochromatic ultraviolet with a primary wavelength of 222 nm) in combination with a special optical bandpass filter (200 to 230 nm) which passes only ultraviolet wavelengths that have no harmful effect on people.

Ushio holds exclusive rights to utilization of the key technology, which was patented by Columbia University (New York, NY) in 2012.

Only 222 nm, which is filtered by a special optical bandpass filter for the rest of the harmful wavelengths, is safe for humans.

The use of Care222 in public places is a safe and effective way to limit the spread and transmission of air-mediated microbial diseases, such as schools, hospitals, stadiums, sports grounds and offices, and this approach may help to limit seasonal infections, the spread of tuberculosis and major epidemics. It’s inevitable far uvc will become part of the new World people are more aware and want to be protected from viruses.

Click here to know more about Ushio’s Care222 technology: www.care222.com

My Lumens Artemis Far UVC Disinfection Devices equipped with Care222 module(filtered far uvc 222nm technology) developed by Ushio.

• Does not cause sunburn, skin cancer or cataracts

Ultraviolet rays with a wavelength of 222 nm are absorbed by the cornea of ​​the stratum corneum of dead cells, so they do not cause damage such as sunburn, skin cancer, and cataracts.

• Virus suppression / sterilization

Ultraviolet rays with a wavelength of 222 nm destroy the DNA / RNA structure of viruses and cells, and suppress and sterilize them.

• Continuously disinfecting in occupied space but not harmful to skin and eyes of people, which could be used in dental offices, medical rooms, high-end offices, elevators, hospitals, class rooms, etc.

Care for you, Safe for you, and Protect you!


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