RE: Calling all laser experts

["Leonowich, John A" <john.leonowich@pnl.gov>]

This post below is not quite correct.  Class 2 lasers rely on the aversion
response, which is why the Accessible Exposure Limits for these visible lasers
are based on a 0.25 exposure and limit their power to less than 1 milliwatt.
This is not true for Class 3a, which can be up to 5 milliwatt, hence the problem
with these consumer products.  True, the probability of retinal damage is small,
it is not ZERO.

Read the paper.

jal

	-----Original Message-----
	From:	Bult, James [SMTP:james.bult@msfc.nasa.gov]
	Sent:	Thursday, October 29, 1998 6:05 AM
	To:	Multiple recipients of list
	Subject:	RE: Calling all laser experts

	The class 3a lasers will supposedly not produce any permanent damage
unless
	you INTENTIONALLY stare into the beam.  The logic is that the natural
	aversion response - i.e. within 0.25 seconds you will either blink or
turn
	your head - is sufficient to prevent any permanent damage.

		The trouble is that with visible and some near IR wavelengths,
you
	get retinal damage if there is an injury.  Retinal damage is forever.
I've
	read about a few kids who have damaged their retinas by intentionally
	staring into the beam. 


		Jim Bult
		NASA MSFC RSO/LSO----------
	> From:
	>
elizabeth_algutifan@wssrap-host.wssrap.com[SMTP:elizabeth_algutifan@wssrap
	> -host.wssrap.com]
	> Reply To: 	radsafe@romulus.ehs.uiuc.edu
	> Sent: 	Thursday, October 29, 1998 7:43 AM
	> To: 	Multiple recipients of list
	> Subject: 	Calling all laser experts
	> 
	> Hey Radsafers,
	> 
	> I took my kids to the mall here in St. Charles last night.  My older
son
	> had
	> been begging me for a week to get him a "cool laser" to use on
Halloween
	> night
	> ("All the other kids have one, Mom," he pleaded).  The first gift shop
we
	> came
	> to had some key chains hanging near the cash register.  My son
immediately
	> recognized them as laser key chains, so I picked one up and looked at
it.
	> It
	> had a warning label that said it was a Class IIIa, red laser in the
	> 660-680 nm
	> wavelength range.  It said "Keep out reach of children" (not my typo;
an
	> import
	> I guess) and "Do not point directly in the eyes" (well, yeah, that
makes
	> sense!)
	>  It was selling for $14.99.  I did not buy it for him (because I know
	> someone
	> will ask).  Of course, I know that these key chains are becoming very
	> popular
	> among school children, as are laser pointers and other types of laser
	> devices
	> that are sold over the counter in some retail stores.  Our local
school
	> district
	> has just made a rule forbidding children to bring any type of laser
	> devices to
	> school under any circumstances.  A child at my kids' school was just
	> suspended
	> for bringing a laser pointer to class (a third grader).
	> 
	> Now, my question is, isn't a Class IIIa laser a pretty severe ocular
	> hazard? And
	> what can we as health physicists do about it?  I'm no expert in this
	> field, but
	> the bits and pieces I've read from studying for the CHP exam indicate
to
	> me that
	> it's an immediate ocular hazard if intrabeam viewing occurs.  I'd like
	> others'
	> thoughts on this issue; I was so upset last night about these things
being
	> in
	> plain view in retail stores (and at a child's eye level) that I was
	> thinking
	> about calling up the FDA.  This seems to be a significant acute
radiation
	> issue
	> to me, that you folks will be interested in.  I hope I'm not
overreacting,
	> and I
	> think I am not.  Thanks for the help and advice.
	> 
	> Elizabeth Algutifan,
	> Environmental Health Physicist
	> WSSRAP
	> St. Charles, MO
	> Elizabeth_Algutifan@wssrap-host.wssrap.com
	> 
	>
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