When somebody gets up in front of a crowd and yells at the top
of their lungs that everybody must have 4" pipe over every
soldering station because of "fumes", even though there's no real
evidence to support it medically,
Every reference you can find about brazing fumes (and there are lots
of them) says that there is no real danger as long as proper
ventilation is supplied. As with almost any of the hazards we
encounter in the studio proper safety practices will handle the
issue and sometimes that means a 4" pipe at each station. But that is
not typically a good ventilation setup. A good book on the subject of
ventilation is Industrial Ventilation: A Manual of Recommended
Practice currently in its 25th edition. It is not an easy read and
not cheap at $79 new but if you can get a used copy or get your
library to get it for you it has a tremendous amount of
James Binnion @James_Binnion
James Binnion Metal Arts
Every reference you can find about brazing fumes (and there are
lots of them) says that there is no real danger as long as proper
ventilation is supplied.
Jim and I (and Jo-Ann) have know each other for years, though we live
in different states, now. I think it’s safe to say that we have a
mutual desire not to butt heads ;}. There’s a reason why I’m posting
again, which I’ll get to. If you read the three links that Jim posted
today (yesterday), you’ll find a common thread. The PDF document in
particular says that 1 air change/hour (which is how HVAC rates
things much of the time), and 2 or even three will not be excessive.
Your typical bathroom fan does about that for the size of the room.
That is unless you have why I’m writing again - cadmium. I had a bout
of metal fume fever once because I took cadmium casually - I had
ventilation but not enough. In my case it was unpleasant but not
severe. There’s another thread here where someone suggests using
paste solder to solder jump rings closed, which I think is good
advise. But be aware that gold paste solders in particular often
contain cadmium, and the combination of paste and flux creates a
more unique situation for fumigating a room than the same solder in
sheet form. For myself, we have a cadmium-free shop, and I would
recommend that everyone do the same. But it is the case where you
need to be especially aware of real dangers.
But be aware that gold paste solders in particular often contain
cadmium,
Thanks for pointing this out. It is something I had simply not
thought of. At present, I use sterling silver strip solder which is
cadmium free but was considering trying the paste solder to solder
jump rings in chains. It didn’t occur to me. I will check now you’ve
mentioned it.
The PDF document in particular says that 1 air change/hour (which
is how HVAC rates things much of the time), and 2 or even three
will not be excessive. Your typical bathroom fan does about that
for the size of the room
Typical HVAC rating is in CFM (Cubic feet per Minute). Air Changes
per Hour can be calculated by (CFM x 60 minutes) / volume of the
room in cubic feet.
Also, Please be aware that the exhausted air must be replaced from
somewhere. There are availabel Heat Recovery Ventilators which will
recover some of the heat (or cooling) from the exhausted air; puting
it back into the replacement air.
Lastly, and far from least, always try to get a little more
replacement air (makeup air) than is being exhausted and used for
combustion. The air should push out through a door / window when
everything is running and the door / window is cracked open
slightly. This will help to avoid a concentration of fumes, dust,
virus etc. etc. This process of having a room is best illustrated by
operating rooms. The operating room is run at the highest “positive
pressure” followed by the recovery room and then the surrounding
areas so that the air flow is from the room outward except where
specifically being exhausted.
I hope this helps in keeping everyone safe and to use common sense
in their workshop ventilation.
No butting heads here There is no question about cadmium fumes
being extremely dangerous (toxic and carcinogenic ) and I try to
make
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
(Precious metal products | Johnson Matthey)
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
the design.
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.
Regards,
Jim
James Binnion @James_Binnion
James Binnion Metal Arts
There is no question about cadmium fumes being extremely dangerous
(toxic and carcinogenic ) and I try to make sure I don't buy any
solders that contain it if possible
Not only that but if one uses a fair amount of cadmium over the
years, it will build up wherever it goes, especially inside your
ventilation system. It’s literally toxic waste.
Keep in mind that any jewelry that you have personally not made from
new gold may or may not have been made with Cadmium solder. If you
do any repair work, you must assume that it was made with Cd solder.
Personally, I use some Cd solders, & have for nearly 40 years.
Anytime that I have any blood work done for any reason I have a Cd
test run at the same time, & have never shown a positive! Also some
of the substitutes for Cd may well be no safer. Good luck, No! I try
to pay attention to safety. I vent my polisher outdoors. Yes, I loose
some gold but think that I stay safer, which is more important that
anything else. When ventilation is not a sure thing. I wear an the
correct filter mask! See your welding supplier.
There is no question about cadmium fumes