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From: wtm@neoucom.UUCP (Bill Mayhew)
Newsgroups: comp.terminals,comp.sys.ibm.pc
Subject: Re: screen cover to shield user from emissions
Message-ID: <614@neoucom.UUCP>
Date: Sat, 4-Jul-87 13:35:34 EDT
Article-I.D.: neoucom.614
Posted: Sat Jul  4 13:35:34 1987
Date-Received: Sun, 5-Jul-87 07:38:03 EDT
References: <3392@sdcsvax.UCSD.EDU>
Organization: Northeastern Ohio Universities College of Medicine
Lines: 50
Keywords: screen emissions radiation
Summary: Probably not worth your money... LCD screen would be a better bet.
Xref: mnetor comp.terminals:341 comp.sys.ibm.pc:5323


	About a year ago we tested several different types of
terminals and CRT screens for personal computers in our building
for emission of ionizing radiation.  I don't have quantitative
figures at hand, but all screens gave off very little radiation.
The safety officer concluded there ought to be little health risk
unless you routinely sit within an inch or two of the screen, which
isn't likely.

	Chances are pretty good that the so-called radiation filter
screens would not significatly reduce the amount of radiation
reaching the user.  Remeber that they do very little to reduce the
emission from the sides and bottom of the case.

	There is a very, very tiny amount of merit in the
protective CRT screens in that they may tend to reduce, slightly,
the static electricity build-up.  This ought to slightly reduce the
likelyhood of computer crashes due to static discharge.

	We've found that the most objectionable aspect of CRT
screens is that some emit very intense ultrasonic acoustical
energy.  While I'm not a physician, I'd imagine that this has a
greater physiolgical impact on computer users than RF energcy
coming from CRTs.  Some CRT terminals emit a very high pitched
whine (probably ~15 KHz) that I can hear;  I've found it very
uncomfortable to work at those terminals for more than a short
time.

	My suggestion would be to look into getting a computer that
is equipped with an LCD or plasma display type screen, if you are
concerned with RF emissions from CRTs.  The voltages present in
LCDs and plasma screens is quite low: ~200 volts or less.  That
should prevent any sighnificant high energy radiation from being
generated.  Note, however, that some plasma screens do emit a
discernible audio whine at ~2 KHz.  While not dangerous, such a
whine might prove distracting if the computer is used in a very
quiet area.

The newer "turbo" models of the Zenith Z-181 can make quite
acceptible desktop units, if you feel avoiding radiation is that
important.

The above does not reflect any policy or medical opinions of my
employer or the State of Ohio.  Opinions expressed are strictly
personal.

Bill Mayhew
Division of Basic Medical Sciences
Northeastern Ohio Universities' College of Medicine
Rootstown, OH 44272-9989  USA    phone:  216-325-23511