Code of Federal Regulations/Title 29/Chapter XVII/Part 1910/Subpart Z/Section 1910.1000/Table Z-3

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Table Z-3—Mineral Dusts
Substance mppcf mg/m³
      Quartz (Respirable)     250 b  
10 mg/me
      Quartz (Total Dust) 30 mg/m³
   Cristobalite: Use ½ the value calculated from the count or mass formulae for quartz
   Tridymite: Use ½ the value calculated from the formulae for quartz
Amorphous, including natural diatomaceous earth 20 80 mg/m³
Silicates (less than 1% 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% SiO2 2.4 mg/me
   Respirable fraction greater than 5% SiO2 10 mg/me
Inert or Nuisance Dust: d  
   Respirable fraction 15 5 mg/m³
   Total dust 50 15 mg/m³


Conversion factors: mppcf × 35.3 = million particles per cubic meter = particles per c.c.

a. Millions of particles per cubic foot of air, based on impinger samples counted by light-field techniques.
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.
c. Containing less than 1% quartz; if 1% quartz or more, use quartz limit.
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.
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/m³ in the table for coal dust is 4.5 mg/m3K.