Draeger gas pum and test tube for ozone (C) D FriedmanXenon Lamp Disinfection Ozone Effects
Possible Ozone byproduct of Xenon disinfection system?

  • XENON LAMP OZONE OUTPUT? - CONTENTS: Reader asks about possible hazardous levels of gases including ozone & complains of chlorine odors when working in hospital where Xenon lamp disinfection system is used
  • POST a QUESTION or READ FAQs about using xenon lamp disinfection & ozone generators to kill odors or mold: dangers & false claims & about how to get rid of odors caused by ozone overdosing
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Xenon disinfection system output, gases, odor question:

At our hospital operating room we are using the Xenex® robot to kill C-diff and other bacterias harmful to staff and future patients. It smells like getting out of a highly chlorinated pool. This exceeds OSHA standards. How do I get the proper department to research this?

This article series discusses the problem of oxidation of building materials from excessive ozone exposure and the horrible chemical smells that may follow such mistakes. We describe how to track down which building materials were over-dosed with ozone and are now giving off a new stink, and we explain how to cure that problem. (Note: other uses of ozone as a disinfectant can be effective and are important in many applications.)

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Ozone as Possible By-Product of Xenon Light Disinfection Methods

Reader Question: Xenex® robot in use for hospital disinfection seems to be producing high levels of ozone

31 August 2015 PhilB said:

At our hospital operating room we are using the Xenex® robot to kill C-diff and other bacterias harmful to staff and future patients.

Xenex claims their machine complies with OSHA regulations of .01ppm over an eight hour period. I have to run this ozone generating device 25+ times a night for ten minute cycles. There is a one minute grace period while the light retracts before I am alerted to reenter the room to move it to another spot. 2-3 shots per room every night.

Since I have been running this machine, I have a sore throat during my shift and my eyes burn at the end of the six hour burn-off.

Your article says,"Experimentation has shown that the odor of ozone can be detected and identified by most people at a concentration of from 0.02 to 0.05 ppm (parts ozone per million parts air + ozone)."

It smells like getting out of a highly chlorinated pool. This exceeds OSHA standards. How do I get the proper department to research this?

Reply: Xenon lamp disinfection is not itself an ozone treatment method but might produce ozone gas indoors

Phil, by your accounting you're running the equipment for more than four hours each night.

The Xenex® robot (Xenex Disinfection Services 121 Interpark, Suite 104 San Antonio, TX 78216 Tel: 1-800-553-0069 Website: is using "pulsed Xenon" a "UV" disinfection system.

While I'm no expert on UV disinfection by light in hospitals, it is apparent that the hazard and thus the short grace period, is a risk of exposure of the eyes to intense UV light. As long as the light is OFF when you enter the room, the light hazard would not be present. Material I've read on Xenon light disinfection cited no toxic byproducts. More clinical trials may be needed however to study the efficacy of the approach.

Xenon light disinfection is not an ozone disinfection method. Ozone disinfection uses a highly-reactive oxygen molecule O3 to oxidize materials. Xenon disinfection uses millisecond pules of an intense light at 200-320nm wavelength range for 8-12 minutes over 2-3 doses as its disinfection approach.

Ozone production and Xenon light has been discussed and the relationship between light in the UV range and ozone production has been cited by Salvermoser (2003 & 2008) and Schalk (2006) and others.

The influence of water vapor on photochemical ozone generation has been investigated. Tests of a coaxial ozone generator driven by an efficient, tubular, 172 nm xenon excimer lamp revealed that ozone saturation concentration strongly depends on moisture concentration in the process gas.

In order to adequately model the data, catalytic ozone destruction by OH and HO2 radicals formed by reactions with trace amounts of water vapor in the process gas had to be included in the photochemical ozone production rate equation system. Based on the model, optimized ozone photoreactor designs for ambient air, dry air and dry oxygen are described. (Salvermoser 2008)

Depending on the indoor moisture level, Xenon light can be a ozone generator and it seems to me ( a lay person ) that there could be hazards from Xenon light disinfection unless the proper bulb type is employed. The U.S. Army has made a clear and succincct remark on this concern:

Some types of UVGI lamps generate ozone. This can pose a workplace hazard, and only “ozone free” lamps made with doped quartz should be used for
surface disinfection.
- (U.S. Army Technical Paper 24-001-1114 2014)

And in the U.K. The Health and Safety Executive has commented on a related and potential hazard that is less immediatly obvious:

projection lamps: high-pressure xenon lamps used in cinema projectors emit some UV radiation and also produce ozone. (HSE Guidance Note #38, 2014)

What these suggest to me is that although Xenon disinfection is described by my earlier comments (and by expert research on the topic) it is possible that the procedure might be generating ozone in the area being treated. I suggest contacting Xenex directly to ask them for guidance on that question. I'm asking the company for advice directly as well. Let me know what you're told as what we learn may assist other readers.

(Sept 6, 2015) PhilB said:

When I spoke to the Xenex rep "Celia" she said the odor was ozone.

I sent an inquiry to Xenex through their website and a Mr. Ed Sylvester called me to explain they were within the legal limits of OSHA standards. 0.01ppm
However, in the above article it states ozone can be detected through the olfactory bulb between 0.02~0.05ppm. Now that is each and every time I use this machine 25+ times every night.
If my math were correct 25 x 0.03= 0.75ppm

(Sept 14, 2015) (mod) said:


Based on e-text alone we cannot know what the ozone level is in your building but in general, the sources I've reviewed on this question are in agreement that if you can smell ozone there is probably a higher-than-acceptable ozone level present.

You are right that the low-end of what people can smell is a very low level of ozone indoors - down to 0.02 ppm.

But because ozone is so volatile you cannot assume that it simply accumulates. Depending on the time period between ozone generation, the area volume, concentration and other factors, it is quite likely that by the end of the rest interval the ozone in the area where it was generated is at a much lower level, possibly below the limits of detection.

A more accurate picture is to assume that the ozone level is going up and down during the 15 usage cycles per night - presuming that they are all in the same physical area.

If the ozone is being generated each time in a new area then you cannot add them together to claim a higher exposure level.

But you can assert that if you smell ozone in the work area, you are being exposed to it repeatedly during a work shift. You don't know at what level unless it is measured during the entire time of exposure.

An industrial hygienist with expertise in ozone measurement and exposure standards would be the proper person to consult for an accurate on-site study of what's going on. Unfortunately that's also costly.

Research on relationship between Xenon lamp disinfection & ozone production


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