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Workshop Air Quality

by Bradney W. Simon - © Bench Magazine - 2003
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 (cfm).

Ventilation
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 Purifying
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
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 in diameter.

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.


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