Paul,Brian,
        I also am not a toxicologist, but here's some information I picked
up over  
        the years. I understand it to be true but...........(disclaimer)
         
        The flame retardent used in most - if not all - standard FR4 is TBBA
(tetra-
        bromo bis-phenol A), this works by generating bromine fumes which 
        deprive the fire of oxygen and therefore make the laminate self 
        extinguishing.Some bromine flame retardents can produce
        dioxins. TBBA is said not to do that. 
        Bromine is given off when the laminate burns but I'm not sure if
bromine
        is given off when the laminate is heated to a certain temperature. 

        For more information on flame retardents, try these sites:-

                http://www.bsef.com
                http://www.firesafety.org
        For the summary of a study into flame retardsnts try:-

                http://www.surrey.ac.uk/PRC/

        FR4 laminates are available without bromine, they are called halogen
        free laminates and are usually based on phosphorous or
        nitrogen compounds.

        hope this helps
        geoff layhe
        www.lamar-uk.co.uk
> ----------
> From:         Brian Ellis[SMTP:[log in to unmask]]
> Reply To:     TechNet E-Mail Forum.;Brian Ellis
> Sent:         10 February 2000 07:45
> To:   [log in to unmask]
> Subject:      Re: [TN] FR4 Flame Retardant Agents
> 
> Paul
> 
> Am not a toxicologist, but I understand that the organobromides are
> loosely crosslinked
> into the epoxy and that they function by releasing hydrogen bromide and
> some other
> nasties on heating beyond about 350°C. This HBr is the actual
> extinguishing agent. HBr
> is decidedly very toxic and corrosive. Most organobromides are more or
> less toxic and
> environmentally unfriendly. Some of the other released compounds may also
> be
> ozone-depleting. However the quantities are relatively small.
> 
> FR-4 without the organobromides is called G-10 and supports continuous
> combustion in
> air. It also produces toxic vapours, although less so and, of course, no
> organobromides.
> 
> Brian
> 
> Paul Klasek wrote:
> 
> > Could you fellows enlighten me on toxicity of this additives please ,
> > and what goes into "standard" FR4 ?
> >
> > Debate circulates about what harm can charring board do in a ventilator
> :
> > With or without retardant :
> > How far is the standard glass laminate prone to ignition/combustion/char
> and
> >
> > what would be the effects of toxins generated ?
> >
> > Thanks a lot
> >
> > Paul Klasek
> > http://www.resmed.com
> >
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