Date: Thu Aug 12 1999 - 12:56:29 CDT
In examining the regulations pertaining to paper dust, there are two areas of
focus. There are indoor air quality and safety concerns and the other
involves emissions to the atmosphere, which is considered an air pollutant.
At the federal level, the agency responsible for indoor air quality is the
Occupational Safety and Health Administration (OSHA). The federal agency
responsible for air pollution is the Environmental Protection Agency (EPA).
There are state equivalents to both EPA and OSHA, although not all states
have an authorized state OSHA, but all have state and in some areas, local
EPAs. This summary will only address the requirements associated with safety.
The first OSHA regulation sets out requirements for indoor air quality or
worker exposure. In order to protect employee's health, OSHA has established
Permissible Exposure Limits (PELs) for various dusts, vapors, and fumes at 29
CFR 1910.1000, Z Tables. The PELs are measured over an eight-hour time
weighted average. OSHA has established a PEL of 5 milligrams/cubic meter for
cellulose dust. Since paper is made out of some form of cellulose, this would
be the applicable limit. Cellulose and paper dust is classified as nuisance
dusts because they do not pose any significant health hazards and only
present a comfort problem.
The other set of regulations addressing the fire and explosion safety issues.
According to OSHA's regulations for electrical safety at 29 CFR 1910.339,
areas where there are dust hazards or potential dust hazards are classified
as a Class II, Division 1. Areas where hazardous concentrations of dust are
not likely Class I areas are those involving highly flammable gases or
vapors. Class II areas are those areas with combustible dusts and Class III
areas are those with combustible fibers or flyings. Under each Class, there
are subdivisions and classes called groupings.
Class II, Division 1 areas are those locations where combustible dust is or
may be in suspension in quantities sufficient to produce explosive or
ignitable mixtures, where dangerous conditions would be created due to
frequent equipment failure, or where electrically conducting dusts are
involved, such as metal dusts. Class II, Division 2 locations are those areas
where dust is not normally present in concentrations to cause a fire or
explosion, but deposits of dust might interfere with heat dissipation from
electrical equipment. It also addresses those areas where dust could become
suspended in air due to infrequent equipment failure or abnormal operation.
According to OSHA's regulation for electrical system safety designs (29 CFR
1910.307), Class II, Division 1 and Class II, Division 2 areas are defined as
hazardous locations. The regulations require that equipment, wiring, and
fixtures used in these areas are approved for use in them. The standard
references the National Electric Code also known as National Fire Protection
Agency's Code 70 as a source for specifications.
Factors that influence the degree of hazards associated with dusts includes
the specific chemical composition, size, shape, concentration, moisture
content, and presence of other contaminants such as oil or ink mist. Most
dusts have minimum ignition energies of several millejoules.
Obtaining specific dust concentrations along with the appropriate other
reference data (e.g., shape, size, moisture content, etc.) has been
difficult, as there does not seem to be one single reference source for this
information. According to one reference, the minimum ignition temperature for
wood flour, which is close to paper dust, is about 40 millejoules. The energy
in an electrostatic spark is about 25 millejoules, which is fairly close to
that needed for paper dust.
For three references found, minimum concentration of dust gave ranges from
0.055-1.00 ounces/cubic feet, 0.09-0.85 ounces/cubic feet, and one gave an
absolute of 0.90 ounces/cubic feet. Only one reference gave a maximum
concentration range of 19.98-99.92 ounces/cubic feet. The references I have
are "Dust Explosions in Process Industry", a National Safety Council Bulletin
based on a Bureau of Mines Report from 1968, and several journal and magazine
The concern with dust fires and explosions is two-fold. The first is the
actual generation of it and the second is dislodging it after settling. Dust
tends to settle and stay in the area where generated, while gas and vapors
tend to disperse and travel. While a small cloud of dust could ignite and
cause no immediate damage, it could dislodge accumulated dust causing a
larger explosion. There have been several fires and explosions reported in
the printing industry due to the dislodging of accumulated dusts in plants.
In one instance, there was a problem with a press that caused the building to
shake, dislodging the dust above the dryer resulting in a large explosion
injuring several workers.
Without specifically measuring the dust concentration, it is very difficult
to determine the exact amount of dust necessary for a fire or explosion to
occur. Several articles and sources contacted stated that is visibility is
obscured at a distance of 2-5 feet, then a fire or explosion hazard would
definitely exist. Another indicator of high dust levels is the horizontal
surfaces in and near the dust generating areas. If enough dust accumulates to
hide the color of the surface, then it should be removed.
Controlling dust clouds involves a variety of approaches ranging from
providing adequate ventilation, proper humidity levels, dust and explosion
proof equipment, wiring, and fixtures, and controlling other sources of
ignition. Isolation via enclosures has also helped contain dust and the use
of dust filters Controlling dust accumulation requires frequent vacuuming of
the dust. Never use compressed air to blow accumulated dust off surfaces.
I have copies of several studies on this topic. If you want copies, let me
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