# B How to test for UV rays?

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1. May 27, 2016

### Frozen

Hi everyone, I suffer from Delayed Sleep Phase Disorder: https://en.wikipedia.org/wiki/Delayed_sleep_phase_disorder

I've been taking sleeping pills for it for years (without them, I'd never be up in time for work) but have recently become concerned about adverse consequences of long-term use, mainly increased risk of dementia. I've been reading about lightboxes as an alternative treatment: http://www.maplin.co.uk/p/maplin-10000-lux-full-size-sad-light-a20hw

I'm worried about using them because of UV rays (cancer runs in my family). The manufacturers claim their lights don't emit UV rays, but I'm naturally mistrusting. How can I test the lightboxes to be absolutely sure?

2. May 27, 2016

### Staff: Mentor

There are various things that react to UV, beads, various fluorescent dyes, UV photodiodes, ...
Depending on the sensitivity, you might also need a filter that blocks visible light (especially for photodiodes).

3. May 27, 2016

### Andy Resnick

You are right to be concerned- the light sources in that box you posted are fluorescent bulbs. A sheet of acrylic (1/4" is plenty thick) will block any residual UV. If you want to make quantitative measurements, tho, it's going to be expensive and time-consuming.

4. May 27, 2016

### ogg

1."cancer runs in my family". I have no idea what that means. Cancer is not a disease. It is a term used to describe a multitude of diseases with multiple causes and a multitude of genetic susceptibility factors. But, perhaps you meant "skin cancer runs in my family".

2. "to be absolutely sure" As a (hopefully) gentle reminder of what you (should have) learned in secondary school: if you want absolute certainty, find a religion - science is not in the absolute truth business. But, perhaps you meant "with a high degree of confidence". In which case, I suggest you contact a manufacturer with a good reputation and ask them. If they claim that their device emits zero UV, you should first challenge them on that (since it can't be "absolutely" true - but it can be below limits of detection and register 0 on a particular measuring device). If they aren't able to (might take some time to find an engineer or technologist who knows what they're talking about) give you a satisfactory answer, then move on. This approach requires you to learn more about what an acceptable daily dose of UV is, and a lot about calibration of measuring instrumentation. I'm a bit concerned that you think that "UV" is one thing rather than a range of electromagnetic wavelengths spanning the range between violet light and x-rays, with DIFFERENT exposure risks.

3. A 30 second Google search on "UV light meter" located dozens of instruments for sale between US$40 and US$1000. A quality instrument will state at least two things: range of wavelengths it is sensitive to and precision of measurement. The cheaper instruments will only measure watts (or similar measure) totaled over its range of sensitivity. You can improve this by buying filters, but good ones aren't cheap. There are much more expensive instruments which will measure the intensity of the UV light's spectrum, usually UVA/B or UVC are done with different sensors/instruments, as well as provide calibration standards. Actually, I'd not buy a meter unless the mfg provided me with the instrument's sensitivity (a graph of watts vs wavelength, for example). If they didn't have that, I'd suspect they were selling junk.

4. Why not ask a dermatologist? Also, museums are careful to monitor UV light exposure, you may be able to find out more from them.

Last edited by a moderator: May 27, 2016
5. May 27, 2016

### Staff: Mentor

6. May 27, 2016

### pixel

Online reviews of these lamps don't give a lot of confidence in their quality so your concern about the UV is justified. You could ask the manufacturer if each unit is tested for UV before it is shipped and how the UV is handled. If it's the plastic diffuser that's absorbing the UV, then as long as it's in place you might be assured. If they are relying on the phosphor coating in the bulbs, it's possible for bits of that to fall off during the manufacturing process, leaving bald spots.

7. Jun 13, 2016

### Frozen

Thank you for your replies, folks. Some very useful stuff here - I've 'liked' a lot of posts.

Thank you, berkeman. And ogg, if we're going to be needlessly pedantic (do you find that speaking to people like that gets you far in life?), maybe care to explain this to me if "cancer is not a disease": http://www.who.int/classifications/icd/adaptations/oncology/en/

I don't know any dermatologists and I live in a rural area so there aren't any museums around me.

8. Jun 13, 2016

### sophiecentaur

Google is your friend here. You can search for all the information you need about the regulations and standards associated with this stuff. You don't appear to have found an actual 'expert' on this topic, here on PF and you are in as good a position as any of us to access the information you need to reassure you.
I have to warn you that your quest may be more than a five minute job. There may be many blind alleys in your search and you may even need to subscribe (with money) to some of the sources. Look upon it as an Insurance Premium and then the occasional few Pounds / Dollars won't hurt so much.
PS You can probably be reassured about the quality of legitimate imports and locally made equipment if you live in one of the better informed countries of the World.