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how to measure UV lamp.

By Ismail Ceyhan | 14 Oct, 2015

Dear Volchenkov,

I need some urgent information about how to measure UV lamp.

I am triying to measure the UV lamp efficacy and UV safety zone in certain units of our Hospital. I have already mesaured some of them. I figured out that most of them were around 50uw/cm2 at 1 m from lamp midpoint. Even new ones were not more than 100uW/cm2. It means not effective according to your suggestion. However, according to some reference "Ultraviolet Germicidal Irradiation Handbook UVGI for Air and Surface Disinfection, Wladyslaw Kowalski" says:

Page:213:The irradiance field is mostly confined to the upper zone, where levels are highest, but lower levels of UV will inevitably spread to the room below. Irradiance levels in the stratum are typically about 0.005–0.1 W/m2 (0.5–10μW/cm2) but can be higher depending on ceiling height and proximity to the lamp fixture.

Page 224: These units created a 30 cm wide upper zone and the average irradiance or fluence rate was measured with actinometers to be about 0.44 W/m2(44μW/cm2).

Q1:Did I wrong measure?



Edward Nardell, MD Moderator Replied at 8:16 AM, 14 Oct 2015

Two of the major barriers to using upper room UVGI are: 1) the ability to
measure fixture output properly with a well calibrated meter focused on 254
nm wavelength and proper measuring method; and 2) design and manufacture of
fixtures that deliver enough UVGI into the upper room while shielding
occupants in the lower room. Neither of these are difficult to achieve,
but if you don't have or cannot obtain a good meter or well-designed
fixtures, a highly effective upper room UVGI installation can be difficult.

Dr. Kowalski's work has been mostly for in-duct UVGI. For upper room UVGI
or recent publication in the Am J Resp Crit Care Med is your best source of
guidance. In that study we looked for fixtures that would deliver a total
fixture output of 20 mW/m3 room volume. Our best fixture delivered a total
fixture output of 0.5W. Measuring UV irradiance at 1 meter is just a
quick estimate and we looked for fixtures that measure 250 uW/cm2
mid-fixture at 1 meter. That is a high standard and I am not surprised to
hear that you are getting only 100 uW/cm2. Again, what really matters is
total fixture output. Dr. Steve Rudnick will soon publish a paper on how
to estimate that using a well-calibrated meter that can be used directly
over the face of the louvered face of the fixture - measuring the entire
output in a systematic fashion. That paper has not yet been published.
Such measurements he found corresponded with gonioradiometry measurements -
the gold standard approach.

From what you told us I cannot say if your meter is correct (calibrated),
your measuring method is correct (probably), or that your fixtures are
properly designed (there are very few well-designed fixtures on the
market). Can you provide more details, and maybe even a photo of the

Grigory Volchenkov, MD Moderator Replied at 8:42 AM, 14 Oct 2015

Dear Ismail,

Hope you clarify the design of the upper room UVGI fixtures you measure.

In addition to Ed's suggestions I would add that if you measure 254 nm UV-C irradiance in upper room space at 1 m from the lamp center correctly, such low values (100 uW/cm2 or less) can be caused by low quality of UV lamps. You could send the lamp (not only fixture) picture and data on it's manufacturer and model.

Is there ozon odor in the irradiated rooms?

Grigory Volchenkov

Ismail Ceyhan Replied at 9:08 AM, 14 Oct 2015

Dear Dr. Nardell

Thank you very much for your prompt reply. I will sent you more information and some pictures our fixed UV lamp. as soon as possible for more discussions.

Best Regards.

Ismail ceyhan

Tshwarelo Mathebula Replied at 9:57 AM, 14 Oct 2015

Greetings Ismail.

It is important to note that you are trying to measure the irradiance at the upper room. This is markedly different from the UV lamp output, the lamp output is higher than the irradiance that you would measure at 1 m from the midpoint. This is due to the louvers on your fixture (i.e if you have a louvered fixture). It is always advisable to not only measure at a fixed point, you might need to slightly move your sensor up and down to determine the absolute maximum at a given point, there always exist a possibility of one making measurements directly at the louver.

One of the facts that would help is to know both the ceiling height, the height which your fixtures are mounted at and the height that you place your sensor for taking your measurements. It would also be important to understand if your meter has been calibrated and when. Some meters will have multiplication factors that you need to take into account to get a more accurate reading.It would also be important to understand what is the total UV output relative to the total electrical input, that would greatly assist in determining the efficiency of your lamp and ultimately your fixture.


Ghanshyam Bhatta Replied at 1:01 AM, 15 Oct 2015

Dr. Nardell statements is very clear and fact for developing world.

Ismail Ceyhan Replied at 5:27 AM, 15 Oct 2015

Dear Nardell and Volchenkov,

Thank you for fruitful reply. I am sending the photos that are UV fixture of our settings. As you will see two types of lamp we have. There is no louvered fixture for UV. lamp. Most of them (almost all) are OSRAM and 15W. Our UV meter is brand new and calibrated by manufacturer. It possible to remove or move shield while the measurement and I did so. The ceiling height is depend. In some setting/s is/are 3 m or a bit higher or shorter. The others are around 2.5-2.7m. The height which our fixtures are mounted around 2.1-2.3 m or a bit higher but not less than 1.9 m. You will find some pictures as attachment.

best regards.

Attached resources:

Ismail Ceyhan Replied at 5:54 AM, 15 Oct 2015

One more thing; one report says: 40-50uW/cm2 is enough.??. (Report is included).

Attached resource:

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