Hi All

I used to deal with Laser Safety but have not for some time. As a comment
on
the current thread -- I believe that most lasers used as pointers for
presentations
are probably in the Class IIIA category and should not present a
'significant'
eye hazard however only Class I are exempt from labeling and "Safe".
Remember that 'safe' is often relative. The difference between
DANGER and CAUTION on the label is significant. As you have probably noted
,
the beam of a laser is not visible except when it illuminates a target. In
laboratories a
smoke or dry ice 'smoke' can be utilized to detect the beam. Tools and
instruments
used are 'non-specular' meaning the are flat black or some other
non-reflective surface
so as not to send the beam off in unexpected directions and create a hazard.
Protective
goggles may also be worn.

Lasers have a wide range of use and are not always hazardous -- reading
CDs, grocery
scanners, etc but even some 'non-hazardous' lasers may require specific
precautions when
their housings or shields are removed. They are widely used in surgery
including eye surgery.
Other lasers can cut holes in almost anything!! I wouldn't want to be on
the viewing end
of one of those.

The topic is complex and broad. Generally, shining a light in the eyes is
not a good thing
when it is bright and/or powerful! I would caution against that. I would
consider my feelings to be about the same as looking down the barrel of a
gun!! I can't believe that these laser pointers are as ubiquitous as they
are if there is a significant hazard, There is a risk (precisely what level
or degree, I don't know) and you will note that one of the charts (see
reference below) uses 'time of exposure', 'direct ocular' and 'diffuse
ocular' definitions in dealing with the hazard based on class (determined by
power ratings). There is also a comment about the viewability of Class IIIA
a little further into the discussion.

More info then you would care to know is available at:

http://www.osha-slc.gov/TechMan_data/II_6.html

I had a little trouble with this site although the URL is correct. You may
have to
access it through http://www.osha.gov and select 'laws' and do the search
for 'lasers'
and select the laser safety topic that comes up as number 1 on the list for
me -- then
you will be at the URL I provided. If this site doesn't tell you more than
you want to know,
I'll be surprised! If you want more info, I am sure a search on the web
using any
search engine will generate a wheelbarrow full of stuff.

Bob Taylor
taylorrt at msn.com
Sumner, WA

-----Original Message-----
From: Jack Bowling <jbowling at direct.ca>
To: tweeters at u.washington.edu <tweeters at u.washington.edu>
Date: Saturday, January 09, 1999 12:56 PM
Subject: Re.Laser pointers


>Richard wrote -
>
><snip>
> Although Michael Price decribed some hypothetical situations that might
cause harm upon the eye
>of birds, wildlife, and people, I suspect the odds of actually ever
>causing harm is virtually nil <snip>
>
>While on training back in Toronto in September 1998, I met an airforce
>chopper pilot who was in the process of being medically discharged for
>retinal burning and scarring, apparently caused by a laser device. He
>had been out in the Pacific on manoeuvers accompanied by "watchdog"
>Soviet vessels. He felt a momentary burning sensation in his left eye
>and his fellow officer with him noticed an intense small red light such
>as is typical of lasers located on the Soviet vessel. Although it
>cannot be proven beyond a doubt, the circumstantial evidence suggests
>that he was "hit" by a laser beam, probably of greater power
>than those readily available as audio-visual aids.
>
>The risk is there and real, but at what power levels the risk becomes
>appreciable I do not know.
>
>-----
>Jack Bowling
>Prince George, BC
>jbowling at direct.ca