Xe Arc Lamp Safety: IR NIR Risk Analysis

[cmos]

Hey all,

When it comes to arc lamps, it looks like the safety concern everybody talks about is in regards to UV exposure. This, however, seems to be more suited for Hg sources instead for Xe sources. My question is in regards to whether there should be any concerns with the IR portion of the spectrum. Xe arc lamps have several high intensity peaks in the NIR, so I was wondering if this is of any / should be of more concern in regards to lab safety? My understanding is that NIR light is just as well focused by the human eye as visible light (even though you can't see it) thus making my question even more prevalent.

Just a quick background: I'm coming up with a setup that includes a Xe arc lamp. The arc itself isn't exposed, but the light will be propagated through free space. Of course, there is also the light that leaks out of the enclosure containing the bulb.

If anyone has some experience with this or other useful thoughts, I'd love to hear them!

For quick reference:
Hg spectrum: http://zeiss-campus.magnet.fsu.edu/articles/lightsources/mercuryarc.html
Xe spectrum: http://zeiss-campus.magnet.fsu.edu/articles/lightsources/xenonarc.html

Cheers,
cmos

 

[Andy Resnick]

The main danger of high pressure arc lamps is electrical- they require a very high voltage to spark, and most problems start when someone doesn't pay attention to that.

Next is handling the bulb- never touch the glass with your bare hands. The salt will corrode and weaken the glass, leading to explosive failure.

Since the NIR light is (usually) coupled with the visible, there's little chance of optical damage to your eye- the aversion reflex is sufficient. If you are concerned, you can use a water cell to filter out the NIR.

If you filter out the visible, the NIR could damage your eye: NIR OSHA specifications apply at class IIIA and up:

http://www.osha.gov/dts/osta/otm/otm_iii/otm_iii_6.html#4

 

[cmos]

Since the NIR light is (usually) coupled with the visible, there's little chance of optical damage to your eye- the aversion reflex is sufficient. If you are concerned, you can use a water cell to filter out the NIR.

Thanks for the advice, Andy. My main concern is that when I looked at the spectrum with a spectrometer, some of those NIR peaks were almost two orders of magnitude greater than the average in the visible. So my thinking was that even if the visible light isn't all that bright, the NIR might already be too much. Is this something I should worry about?

I suppose it's just as easy filter out the NIR and not worry about it from there, but I figure it would be good to know this information regardless.

 

[Andy Resnick]

The OSHA document is what you need to check against; to get the irradiance, try using this:
www.lot-oriel.com/site/site_down/ls_irradiance_deen07.pdf[/URL]

find your bulb, do the calculation and compare against the spec. As a rough cut, the peaks appear to have irradiances of about 100 mW/m^2/nm. Taking a peak as fwhm 10nm, this gives 0.1mW/cm^2. The OSHA: ANSI Z 136.1: Long-Term Exposure Limits gives 4 mJ as the figure of merit, which assumes a 7mm pupil (0.38 cm^2) (you're not looking at the light through binoculars, are you? :)) . So your eye receives 0.038 mW, meaning you can stare directly at the bulb for about 100 seconds before there is a risk of damage.

If you are doing that, you shouldn't be in a lab :)

 

[cmos]

Wow, super detailed; thanks for all of that, Andy!

I just found it somewhat curious that there is so much literature on UV safety and laser safety but relatively little when it comes to IR. Interestingly, with the Xe source I've been playing with, I've been able to saturate my detector with the NIR part of the spectrum long before shorter wavelengths do the same.