From the Jan/Feb 2000 issue of Clay Times
This is the second column on respiratory protection and recent changes in related federal safety regulations.
In 1998, the Occupational Safety and Health Administration (OSHA) rewrote the respiratory protection standard. Of all the changes, the most important for potters was the adoption of new standards for the filters that are in masks or in respirator cartridges.
Standards. You may have noticed that the acronym “NIOSH” is always somewhere on masks and respirators. This stands for the National Institute for Occupational Safety and Health. Contrary to common opinion, NIOSH doesn’t “approve” respirators. Instead, they specify the tests that all respirators must pass. There are NIOSH standard tests for both the chemical and the particulate types of filters.
Chemical filter standards have not changed. These filters capture substances potters rarely use such as ammonia, formaldehyde, acids, and organic solvents. We are exposed to many of these substances in kiln emissions, but kiln emissions are mixtures of hundreds of substances, many of which are not captured by any type of filter. Ventilation is the only answer for kiln emissions.
Particle filters are those that capture airborne solid particles and liquid mists. These are the ones potter can use to protect themselves from clay and glaze dusts and glaze spray mists. Picking the right mask for pottery work used to be easy. The filters came in only three types: dust, mist and fume. Now, there are nine different types based on performance.
Performance classes. Particulate filters now come in three different series designated as N, R and P. All of these filters are tested against “fume-sized” particles (0.3 microns). The filters in each series have three minimum efficiency levels95%, 99% and 99.97%. That is: *N95, R95 and P95 filters are certified as having a minimum efficiency of 95%; *N99, R99 and P99 filters are certified as having a minimum efficiency of 99%; *N100, R100 and P100 filters are certified as having a minimum efficiency of 99.97%.
N series filters can be used only in atmospheres containing no oil-based particulates. For example, you should not use the N filters if you were machining metal with cutting oils, or spraying WD40TM. This is not likely in a pottery!
The N filters also have a “time-use restriction.” This means you should only use them for eight hours. The eight hours can be either continuous or intermittent. Intermittent use means that you are using the filter short periods of time, sealing it in plastic ZiplocTM bags between wearings, and will discard the mask when the amounts of time it was used total eight hours.
R series filters can be used whether or not there is oil present. R filters also have a time-use restriction of eight hours of continuous of intermittent use.
P series filters may be used in either oil-free or oil-containing atmospheres. They do not have any time-use restrictions which means they can be used until they are soiled, damaged, cause an increase in breathing stress, or show some other sign that they are worn out. The P100 is the top-of-the- line and the only filter to be assigned the familiar magenta color reserved for the old HEPA or fume filter.
Choosing your respirator. Since it is rare that there is oil mist in the pottery, potters may be able to use any of these filters. To choose the right one, you need to consider two primary factors: 1) the toxicity of the contaminant; and 2) the particle size of the contaminant.
Toxicity. The choice is simple if you are working with highly toxic dusts and powders such as lead, cadmium, chrome, or nickel. In these cases, you should always use a filter with a 100% rating. For example, OSHA requires a 100% HEPA filter be used whenever lead or cadmium is airborne regardless of particle size.
Particle size. Silica flour, metal fumes, pigment powders, other substances known to contain significant amounts of particles in the range of 0.3 microns in diameter require a respirator with a filter efficiency of 100. Coarse grinds or granular materials of moderate or low toxicity may be addressed with one of the less efficient filters.
It would be easier to choose a respirator if suppliers of ceramic clays and chemicals would provide the particle size distribution data on their products. This data is readily available from most of the primary manufacturers. For reasons unknown to me, pottery suppliers rarely pass this information on to their customers.
The data on particle size is usually presented in the form of a graph which indicates the amounts and sizes, from fine to coarse, of all the particles in the product. In some cases, potters are told the “mesh” size for certain products. But mesh is the size of the largest particles that will pass through a screen and tells you nothing about the amounts of finer particles present.
Practical rules. Until you know the particle size of the materials you use, it is wise to use the 100 filters for most operations because many of our colorants can be classified as highly toxic and because free silica is present in amounts over one percent in so many of our materials. You might want some 95s around for wood dust or other non-ceramic activities.
Choosing whether you want an N100, R100, or P100 mask will depend on how you work. If at the end of the day your mask usually looks dirty and bent out of shape, you should buy the least expensive N series mask and replace it frequently. If your masks usually look as good a new at the end of the day, you will save money if you buy the more expensive P100s and take good care of them.
Monona Rossol may be reached at ACTS, 181 Thompson St. #23, New York, NY 10012-2586; (212) 777-0062; e-mail: email@example.com.
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