Page 29 - Advanced Mine Ventilation

12 Advanced Mine Ventilation

coal mining. CFR 30, part 70 deals with health standards, whereas CFR 30, part 75
deals with safety standards in coal mines [6].
All ventilation standards (as shown in Table 1.1) are established by the CFR Title
30 or the threshold limits established by the American Conference of Governmental
Industrial Hygienists [7]. Some excerpts from these vast documents are provided
here to illustrate the safety measures. Reference should be made to the original docu-
ments for details.

1.5.2 Maximum Concentration of Explosive Gases in Coal Mine
Air
The legal maximum concentration of several gases in coal mines are limited by MSHA
as shown below:

Gases Maximum Limits (%)
Methane 1 (intake), 2 (return)
Acetylene 0.4
Propane 0.4
Hydrogen 0.8
Carbon monoxide 2.5
Hydrogen sulfide 0.4

These limits are much lower than the minimum explosive limits of these gases in
air. It will be discussed in detail later in the book.

1.5.3 Some Highlights of Code of Federal Regulations 30, Parts
70 and 75

1.5.3.1 Respirable Dust Measurement
Respirable dust is theoretically defined as particles smaller than 5 mm, but it is actually
measured by the amount collected by the approved sampling instrument on a filter. The
standard for respirable dust requires that the average concentration (of five consecutive
3
shifts) to which a miner is exposed be at or below 1.5 mg/m . In addition, the respi-
rable dust concentration in the intake air to the same working section should be below
3
1 mg/m .
When the respirable coal dust contains more than 5% quartz, the dust standard is
lowered by the following formula:
10 3
Respirable Dust Standard ¼ mg m
Percent Silica