Table
Z-3 Mineral Dusts
|
 |
| Substance |
|
mppcf [a] |
|
mg/m(3) |
|
|
|
| SILICA: |
|
|
| Crystalline |
obsolete |
|
|
Quartz (respirable) |
250 [b]
|
10 mg/m(3) [e]
|
|
%SiO(2) +5 |
%SiO(2) +2 |
|
|
|
| Quartz (Total Dust) |
|
30 mg/m(3)
|
|
|
%SiO(2) +2 |
|
|
|
|
Cristobalite: Use 1/2
the value calculated from the count of mass formulae for quartz |
|
|
Tridymite: use 1/2 the value
calculated from the formulae for quartz.
|
|
|
| Amorphous, including natural diatomaceous earth |
20 |
80 mg/m(3)
|
|
|
%SiO(2) |
| Silicates |
|
|
| (less than 1 percent crystalline silica): |
|
|
| Mica |
20 |
|
| Soapstone |
20 |
|
| Talc (not
containing asbestos) |
20 [c] |
|
| Talc
(containing asbestos) Use asbestos limit Tremolite, asbestiform (see
29 CFR 1910.1001) Portland cement |
50 |
|
|
|
|
Graphite (natural)
|
15 |
|
| Coal Dust: |
|
|
| Respirable
fraction less than 5% SiO(2) |
|
2.4 mg/m(3) [e] |
|
Respirable fraction greater than 5% SiO(2) |
|
10 mg/m(3) [e]
|
|
|
|
%SiO(2) +2
|
| Inert or Nuisance Particulates [d]:
|
|
|
| Respirable
fraction |
15 |
5 mg/m(3) |
| Total dust |
50 |
15 mg/m(3) |
|
Note: Conversion factors - mppcf X 35.3 = million particles per cubic
meter = particles per c.c.
Footnote(a) Millions of particles per cubic foot of air, based on
impinger samples counted by light-field techniques.
Footnote(b) The percentage of crystalline silica in the formula is
the amount determined from airborne samples, except in those
instances in which other methods have been shown to be applicable.
Footnote(c) Containing less than 1% quartz; if 1% quartz or more, use
quartz limit.
Footnote(d) All inert or nuisance dusts, whether
mineral, inorganic, or organic, not listed specifically by substance name
are covered by this limit, which is the same as the Particulates Not Otherwise
Regulated (PNOR) limit in Table Z-1.
Footnote(e) Both concentration and percent quartz for
the application of this limit are to be determined from the fraction
passing a size-selector with the following characteristics:
|
|
| Aerodynamic diameter (unit
density sphere) |
|
Percent passing selector |
|
|
| 2 |
90 |
| 2.5 |
75 |
| 3.5 |
50 |
| 5.0 |
25 |
| 10 |
0 |
|
The measurements
under this note refer to the use of an AEC (now NRC) instrument. The
respirable fraction of coal dust is determined with an MRE; the figure
corresponding to that of 2.4 mg/m(3) in the table for coal dust is 4.5
mg/m(3).
|
|
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