Four areas in
the jeweler's workshop produce harmful substances that MUST be properly
removed from the shop in order to maintain the jewelers' health. The toxic
particles produced are generally chronic in nature. This means that immediate
reaction is not apparent, but twenty or thirty years of continued exposure
can lead to poor health and sometimes early death.
The four areas in the shop that produce toxic particles are:
1. Sink - Where cleaners are used and where electro-plating is handled
2. Workbench -Where soldering is performed
3. Polishing machine
4. Casting area - Where investment is mixed and around the kiln where
the waxes are melted out.
A standard rate of air exchange for the shop is six air changes per hour.
In order to figure this, take the length of the room in feet, times the
width of the room in feet, times the height of the room in feet. This
will give you the cubic feet of the room. If you take this number and
multiply it times six, it will give you the number of cubic feet of air
needed to be moved in an hours time. Dividing this figure by sixty will
give you the amount of cubic feet per minute (cfm) that needs to be removed
from the shop. This number rates exhaust fans and will give you the size
of fan that you need.
Length X Width X Height = Cubic Feet
Cubic Feet X 6 60 = CFM needed
However, this is a general guideline. The changes of air per hour are
not nearly as important as having enough capacity to pull the fumes away
from the breathing zone of the worker. For example, one jeweler working
by himself in a large room does not need as many air changes per hour
as would several jewelers working together in a small room. In the latter
situation, six changes of air per hour may not be adequate. When you have
a number of jewelers producing toxic fumes in a confined space, the air
needs to be rapidly changed.
In order to determine if your ventilation is adequate, you need to determine
if the fumes are pulled away from the work area. Sophisticated equipment
is available to measure this; however, the jeweler can perform a simple
test. Place a piece of crumpled paper on your solder pad in the area to
be tested. Light the paper, then blow out the flame and watch the smoke
that it produces. See if it lingers in the area or if the ventilation
pulls the smoke away from you and out of the workspace. If the smoke moves
out of the area, your ventilation is adequate. If not, you need to move
the hood closer to the work area or increase the velocity of the airflow
Exhaust ventilation is the most popular method of removing contaminated
air from the workshop. Contaminated air is captured in a hood and carried
through ducts to outside the building. Ducts can be installed across the
building and out a wall, or up and out the roof. When determining where
to install the outlet make certain that it is not near a fresh air inlet
or window that may be opened.
Fans are used to pull or push the air through the ducts. Centrifugal
fans installed inside the building are designed to push air though the
ducts. Propeller fans installed at the outlet are designed to pull the
air through the duct. Both types do an excellent job in removing the air.
However, with the propeller fan mounted outside you gain an advantage
of not hearing the noise from the fan and motor in the shop.
Once outside, the contaminated air, which is hazardous inside the confinement
of the shop, is diluted in the atmosphere. The amount of toxic substances
produced in the average retail jewelry workshop fall within the acceptable
levels set by the EPA and OSHA to be released into the atmosphere. However,
these laws may change, forcing jewelry stores to change their ventilation
systems at some point in the future.
A major disadvantage of ventilation systems is that for every cubic foot
of contaminated air removed from the shop a cubic foot of fresh air must
be replaced. If a sufficient supply of fresh air is not provided a partial
vacuum is created in the shop. This reduces the efficiency of the ventilation
system. This fresh air coming in from outside must be heated in the winter
and cooled in the summer, adding to the overall cost of using the unit.
NEVER use Exhaust Ventilation in the polishing room or near the polishing
machine. Always filter the contaminated air from polishing to recover
precious metal waste. If dust is a problem in these areas, ventilation
is not the answer. Better maintenance of the dust collector or a larger
one is needed.
Air purifiers that filter toxic particles out of the air are an excellent
alternative to ventilation. They are more economical to install, as long
runs of ducts do not have to be installed. They are also cheaper to use
as the air is returned to the shop and does not have to be heated or cooled.
They also have an environmental advantage, as they do not expel toxic
substances into the atmosphere.
HEPA is an acronym for High Efficiency Particulate Air. It is an air cleaning
technology first developed during the early days of atomic research. It
was used to clean the air of radioactive particles that might escape and
present a health hazard to researchers. True HEPA filtration is recognized
as the most efficient cleaning media, capable of removing sub-micron size
particles from the air. To be regarded a HEPA filter it must remove at
least 99.97 percent of particles at 0.3 micron in size. A micron is one
millionth of a meter. For comparison, a human hair is 75 to 100 microns
The filtering material is made of very thin glass fibers. They are made
into paper with a thickness and texture very similar to blotter paper.
As particles pass through a HEPA filter, they actually run into one of
the fibers and stick to it by mutual attraction.
Air cannot pass through the filter easily, so a very large area of filter
must be used. To fit a large surface area into a filter the material is
pleated, creating an extended surface. To keep them from clogging, they
are often used with a fabric pre-filter to filter out larger particles
from the air.
True HEPA filters are recommended for the workshop, due to their high
efficiency in removing sub-micron size toxic particles from the air.