[Code of Federal Regulations]
[Title 30, Volume 1]
[Revised as of July 1, 2002]
From the U.S. Government Printing Office via GPO Access
[CITE: 30CFR75.321]

[Page 473]
 
                       TITLE 30--MINERAL RESOURCES
 
  CHAPTER I--MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR
 
PART 75--MANDATORY SAFETY STANDARDS--UNDERGROUND COAL MINES--Table of Contents
 
                         Subpart D--Ventilation
 
Sec. 75.321  Air quality.

    (a)(1) The air in areas where persons work or travel, except as 
specified in paragraph (a)(2) of this section, shall contain at least 
19.5 percent oxygen and not more than 0.5 percent carbon dioxide, and 
the volume and velocity of the air current in these areas shall be 
sufficient to dilute, render harmless, and carry away flammable, 
explosive, noxious, and harmful gases, dusts, smoke, and fumes.
    (2) The air in areas of bleeder entries and worked-out areas where 
persons work or travel shall contain at least 19.5 percent oxygen, and 
carbon dioxide levels shall not exceed 0.5 percent time weighted average 
and 3.0 percent short term exposure limit.
    (b) Notwithstanding the provisions of Sec. 75.322, for the purpose 
of preventing explosions from gases other than methane, the following 
gases shall not be permitted to accumulate in excess of the 
concentrations listed below:
    (1) Carbon monoxide (CO)--2.5 percent
    (2) Hydrogen (H2)--.80 percent
    (3) Hydrogen sulfide (H2 S)--.80 percent
    (4) Acetylene (C2 H2)--.40 percent
    (5) Propane (C3 H8)--.40 percent
    (6) MAPP (methyl-acetylene-propylene-propodiene)--.30 percent