From: Peter Zavon <pzavon**At_Symbol_Here**>
Subject: Re: [DCHAS-L] Laser eye protection question
Date: Thu, 28 Jul 2016 21:28:34 -0400
Reply-To: DCHAS-L <DCHAS-L**At_Symbol_Here**MED.CORNELL.EDU>
Message-ID: 00a201d1e938$85e85010$91b8f030$**At_Symbol_Here**

It appears that St. Ambrose is small enough that it does not have a readily apparent administrative group dealing with occupational health and safety, so I can't refer you there where I would otherwise expect someone to be who was familiar with laser safety. However, any academic institution that uses multiple lasers ought to have someone, somewhere, who is familiar with ANSI Z136.1, the basic laser safety standard. Users of Class 2 and Class 3A lasers are working with low hazard lasers that do not require laser safety eyewear but should still receive some basic instruction in how to use them safely.


As noted by another responder, use of Class 2 lasers does not require eye protection because you get your safety from the aversion response. That is, you have time to blink or look away after the full laser beam enters your eye and before damage occurs. The blink reflex is, I am told, something that happens in a quarter to a third of a second. Damage from a Class 2 laser beam requires at least 100 seconds of continuous direct beam viewing. But the user needs to know that. And, of course, more care may be needed with some Class 2 lasers if collecting or magnifying optics are used. These would be classified as Class 2M lasers in the modified classification system established in Europe some 10 years ago and now acceptable, although not required, in the US.


While Class 2 lasers are by definition only lasers operating in visible light below a specified beam power, Class 3A lasers can be visible, infrared or ultraviolet because the maximum pupillary diameter is at the core of safety with these devices. Class 3A lasers have a maximum beam power but also a maximum power density in the beam. Combined with the maximum pupil diameter, this limits the laser energy that can enter the eye and be magnified/focused on the retina. The result is that for this class of laser extended direct viewing of the beam is to be avoided and protective eyewear is not required - again, unless you are using collecting or magnifying optics with some Class 3A devices.



Peter Zavon, CIH
Penfield, NY




From: DCHAS-L Discussion List [mailto:dchas-l**At_Symbol_Here**] On Behalf Of Ferm, Barret
Sent: Wednesday, July 27, 2016 5:21 PM
Subject: [DCHAS-L] Laser eye protection question


I am seeking help on a laser-safety question from a physics colleague. They need eye protection for the lasers listed below. Any help would be greatly appreciated. Many thanks!

Diode laser:  max < 5 mW; 660-680 nm; class IIIa 


Helium-neon gas laser:  max < 1 mW; 633 nm; class II


Metrologic neon laser:  1.0 mW; class II


Barry Ferm 
Chemical Hygiene Officer
St. Ambrose University Chemistry Dept


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