No butting heads here There is no question about cadmium fumes
being extremely dangerous (toxic and carcinogenic ) and I try to
sure I don't buy any solders that contain it if possible. But with
proper and I must stress proper ventilation the solders that contain
it can be used safely.But I do not recommend their use by studio
metalsmiths because the question about is their ventilation system
good enough is just too hard to assess without a huge amount of work
and specialized equipment.
The section on ventilation in the Johnson-Mathey document
should be read carefully by anyone thinking about using cadmimum
solders. It says:
"A simple local exhaust extraction system such as that used for
welding would require careful design and positioning to capture
all the fume produced because gas/air mixtures have high flame
speeds. If the collector is placed too close to the work then
the high capture velocities needed will disturb the torch flame,
but this kind of system can be used for induction brazing. For
flame brazing a local exhaust system will remove only part of the
fume generated but it would be better than no extraction at all.
Where brazing is carried out in a confined space then a suitable
fume filter face mask should be used providing there is no
question of depletion of oxygen in the atmosphere. Under these
circumstances a helmet fed with fresh air or self contained
breathing apparatus is to be preferred. Care must be taken to
ensure that factory regulations for working in confined spaces
are adhered to."
In regards to cadmium I do not agree with the concept of some being
better than none at all as it is just too hazardous. The article does
reference a design for a soldering booth for torch soldering to
provide a safe working space. It is published by The British
Association for Brazing and Soldering titled "Recommendations for
the Safe Use of Cadmium Containing Filler Metals for Brazing." July
1978. I have not been able to find it on the web so I have not seen
One of the problems with documents like I referenced in the earlier
post is the lack of specifics on ventilation setup. When you are
talking about ventilation you need to specify more than the number
of air changes per hour. The flow direction and flow velocity and
location of the suction are critical to make sure you are getting
rid of the fumes not spreading them around the room and pulling them
past your face in the process. Just because a fan is rated at 200
CFM does not mean it actually will remove 200 CFM from your work
space. You have to look at the whole system, the work space as well
as the air supply and exhaust equipment to make that determination.
The book "Industrial Ventilation: A Manual of Recommended Practice"
is the only place I have ever found real hard on design
of ventilation systems for hazards like we need to deal with.
James Binnion Metal Arts