From: R.Stclair@EBay.Sun.COM (R D St.Clair)
Date: Wed, 27 Jan 93 10:35:19 PST
Subject: Zink Dangers

This is a warning and a request for further information regarding the
use of zink coated electrical conduit in HPV construction.

Thin wall conduit is a readily available material for HPV
construction.  It is cheap, and plenty strong enough in the right
applications.  It is only mild steel, and so is not as strong or light
as cro-molly, but it still might be useful in the early stages of
experementation with different configurations, or for less critical
applications.

It is, however, zink coated for corrosion resistance, and this poses a
health and safety concern with regard to welding or brazing.  When arc
welding the material I have seen the zink gas off and become little
spider weab strands floating around.  I am not sure what form, if any,
the gas off takes when brazing or oxy-acetylene welding.

I am told that this gaseous zink is a DEADLY POISON and will land you
in the hospital or worse.  I am assuming that this is a form of heavy
metal poisoning and is therefore similar to lead poisoning (just my
uneducated guess).

People who weld this material claim to do it in an open space with a
fan to blow the smoke out of the area.  (I am not qualified to
recommend this as an adequate safety precaution.)  Other people
recommend grinding or sanding off the zink in the area of the weld
prior to welding.  (I am not sure how safe this is as it is difficult
to know if you gave gotten it all off, and how far back from the weld
area to clean.)

Knowing this you would think I would be forewarned.  BUT, I brazed
some conduit in the open with no fan and not much breeze.  Now I
notice a tightness in my chest when I breath deeply (hopefully
temporary).  I had not cleaned off the zink, but brazed right through
it.

Does anyone out there have further information on the dangers
involved?  Here are my questions?

1.  Does this cause permanent damage?

2.  Are the effects cumulative?  (like lead poisoning)  Will the body gradualy 
    purge itself of these poisons if given time?

3.  What are the symptoms?  Do they indclude things like loss of mental 
    capacity like lead poisoning does?

4.  Are there accepted safe means of dealing with this?

5.  When the zink gases off, does it simply become gaseous zink, or does it 
    combine with other elements (oxygen?) to form other compounds?  Is it these
    other compounds that are poisonous?

6.  No doubt all welding or brazing produces some poisones or noxous gases.
    What are the comparative risks of zink to these?