[Code of Federal Regulations]
[Title 41, Volume 1]
[Revised as of July 1, 2005]
From the U.S. Government Printing Office via GPO Access
[CITE: 41CFR50-204.50]

[Page 37-38]
 
           TITLE 41--PUBLIC CONTRACTS AND PROPERTY MANAGEMENT
 
            CHAPTER 50--PUBLIC CONTRACTS, DEPARTMENT OF LABOR
 
PART 50-204_SAFETY AND HEALTH STANDARDS FOR FEDERAL SUPPLY CONTRACTS
--Table of Contents
 
            Subpart D_Gases, Vapors, Fumes, Dusts, and Mists
 
Sec. 50-204.50  Gases, vapors, fumes, dusts, and mists.


    (a) (1) Exposures by inhalation, ingestion, skin absorption, or 
contact to any material or substance (i) at a concentration above those 
specified in the ``Threshold Limit Values of Airborne Contaminants for 
1968'' of the American Conference of Governmental Industrial Hygienists, 
except for the ANSI Standards listed in Table I of this section and 
except for the values of mineral dusts listed in Table II of this 
section, and (ii) concentrations above those specified in Tables I and 
II of this section, shall be avoided, or protective equipment shall be 
provided and used.
    (2) The requirements of this section do not apply to exposures to 
airborne asbestos dust. Exposures of employees to airborne asbestos dust 
shall be subject to the requirements of 29 CFR 1910.93a.
    (b) To achieve compliance with paragraph (a) of this section, 
feasible administrative or engineering controls must first be determined 
and implemented in all cases. In cases where protective equipment in 
addition to other measures is used as the method of protecting the 
employee, such protection must be approved for each specific application 
by a competent industrial hygienist or other technically qualified 
source.

[[Page 38]]



                        Table II-- Mineral Dusts
------------------------------------------------------------------------
                   Substance                      Mppcf\e\     Mg/M \3\
------------------------------------------------------------------------
Silica:
  Crystalline:
    Quartz (respirable).......................       250\f\       10mg/M
                                                                  \3\\m\
                                               -------------------------
                                                    %SiO2=5      %SiO2=2
    Quartz (total dust).......................  ...........   30mg/M \3\
                                                            ------------
                                                ...........      %SiO2=2
  Cristobalite: Use \1/2\ the value calculated
   from the count or mass formulae for quartz.
  Tridymite: Use \1/2\ the value calculated
   from the formulae for quartz.
  Amorphous, including natural diatomaceous              20   80mg/M \3\
   earth......................................
                                                            ------------
                                                ...........        %SiO2
                                                            ============
Silicates (less than 1% crystalline silica):
    Mica......................................           20
    Soapstone.................................           20
    Talc......................................           20
    Portland cement...........................           50
  Graphite (natural)..........................           15
  Coat dust (respirable fraction less than 5%   ...........  2.4mg/M \3\
   SiO2)......................................
                                                ...........           or
  For more than 5% SiO2.......................  ...........   10mg/M \3\
                                                            ------------
                                                ...........      %SiO2=2
  Inert or Nuisance Dust:
    Respirable fraction.......................            1    5mg/M \3\
    Total dust................................          505    15mg/M\3\
------------------------------------------------------------------------
Note: Conversion factors--
mppcfx35.3=million particles per cubic meter
 =particles per c.c.
\e\Millions of particles per cubic foot of air, based on impinger
  samples counted by light-field technics.
\f\The percentage of crystalline silica in the formula is the amount
  determined from air-borne samples, except in those instances in which
  other methods have been shown to be applicable.
\j\As determined by the membrane filter method at 430 x phase contrast
  magnification.
\m\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:


------------------------------------------------------------------------
                                                               Percent
         Aerodynamic diameter (unit density sphere)            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 instrument.
  If the respirable fraction of coal dust is determined with a MRE the
  figure corresponding to that of 2.4 Mg/M \3\ in the table for coal
  dust is 4.5 Mg/M \3\


[36 FR 23217, Dec. 7, 1971]