(a) All underground mines, and the surface mills of Subcategory I-C
mines (gilsonite), shall be placed into one of the following categories or
subcategories to protect persons against the hazards of methane and dusts
containing volatile matter. Categories and subcategories are defined as
follows: (1)Category I applies to mines that operate within a
combustible ore body and either liberate methane or have the potential to
liberate methane based on the history of the mine or the geological area in
which the mine is located. Category I is divided into Subcategories I-A, I-B,
and I-C as follows: (a)(1) (i)Subcategory I-A applies to mines that operate
within a combustible ore body and liberate methane and in which-- (a)(1)(i) (A) A concentration of 0.25 percent or more methane
has been detected in the mine atmosphere and confirmed by laboratory
analysis; or (a)(1)(i) (B) An ignition of methane has occurred. (a)(1) (ii)Subcategory I-B applies to mines that operate
within a combustible ore body and have the potential to liberate methane
based on the history of the mine or geological area in which the mine is
located and in which-- (a)(1)(ii) (A) A concentration of 0.25 percent or more methane
has not been detected in the mine atmosphere; and (a)(1)(ii) (B) An ignition of methane has not occurred. (a)(1) (iii)Subcategory I-C applies to mines in which the
product extracted is combustible and the dust has a volatile matter content
of 60 percent or more measured on a moisture free basis1 .
1 Measured by the American Society for Testing and Materials, ASTM D
3175-82, Standard Test Method for Volatile Matter in the Analysis Sample of
Coal and Coke. (This document is available at any Metal and Nonmetal Mine
Safety and Health District Office of the Mine Safety and Health
Administration). (2)Category II applies to domal salt mines where
the history of the mine or geological area indicates the occurrence of or the
potential for an outburst. Category II is divided into Subcategories II-A and
II-B as follows: (a)(2) (i)Subcategory II-A applies to domal salt mines where
an outburst reportable under §57.22004(c)(1) has
occurred. (a)(2) (ii)Subcategory II-B applies to domal salt mines where
an outburst reportable under §57.22004(c)(1) has
not occurred, but which have the potential for an outburst based on the
history of the mine or geological area in which the mine is located. (3)Category III applies to mines in which
noncombustible ore is extracted and which liberate a concentration of methane
that is explosive, or is capable of forming explosive mixtures with air, or
have the potential to do so based on the history of the mine or the
geological area in which the mine is located. The concentration of methane in
such mines is explosive or is capable of forming explosive mixtures if mixed
with air as illustrated by Table 1 below, entitled "Relation Between
Quantitative Composition and Explosibility of Mixtures of Methane and
Air". Table 1 See MSHA Illus. 27
Relation Between Quantitative Composition and
Explosibility of Mixtures of Methane and Air (4)Category IV applies to mines in which
noncombustible ore is extracted and which liberate a concentration of methane
that is not explosive nor capable of forming explosive mixtures with air
based on the history of the mine or the geological area in which the mine is
located. The concentration of methane in such mines is not explosive nor
capable of forming explosive mixtures if mixed with air as illustrated by
Table 1 above, entitled "Relation Between Quantitative Composition and
Explosibility of Mixtures of Methane and Air". (5)Category V applies to petroleum mines. Category V is
divided into Subcategories V-A and V-B as follows: (a)(5) (i)Subcategory V-A applies to petroleum mines that
operate entirely or partially within an oil reservoir; and all other
petroleum mines in which-- (a)(5)(i) (A) A concentration of 0.25 percent or more methane
has been detected in the mine atmosphere and confirmed by laboratory
analysis; or (a)(5)(i) (B) An ignition of methane has occurred. (a)(5) (ii)Subcategory V-B applies to petroleum mines that
operate outside of and drill into an oil resevoir and in which-- (a)(5)(ii) (A) A concentration of 0.25 percent or more methane
has not been detected in the mine atmosphere; and (a)(5)(ii) (B) An ignition of methane has not occurred. (6)Category VI applies to mines in which the
presence of methane has not been established and are not included in another
category or subcategory. (b) Category or subcategory placement or change in placement shall
include consideration of the following: (1) The history and geology of the mine or of the
geological area in which the mine is located; (2) The ore body and host rock; (3) The character, amount, duration, origin, and nature of
methane emission and the presence of explosive dust and inert gases; and (4) Whether or not conditions encountered during primary
or access development are transient or permanent. (c)(1) Gas samples for the purpose of category or subcategory
placement or change in placement, and for determining action levels, shall be
taken in the mine atmosphere. Gas samples taken to determine the nature and
extent of an occurrence under §57.22004 (c) and
(d) may be taken at any location, including the
source, point of entry and the mine atmosphere. (2) Tests for methane shall be made with hand-held
methanometers, methane monitors, atmospheric monitoring systems, devices used
to provide laboratory analysis of samples, or with other equally effective
sampling devices. However, only methane samples that have been confirmed by
laboratory analysis shall be used for category or subcategory placement or
change in placement. (d) Each mine and mill shall be required to operate in accordance
with the safety standards applicable to its particular category or subcategory.
