7.8 Explosiveness of Mine Gases
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Methane is a combustible gas which when mixed with air forms an explosive
mixture. When the methane concentration is between 5 and 15%, the mixture is
extremely explosive. From a toxicological point of view, this gas displaces oxygen.
Question 7.2 Indicate with an x the gases meeting the characteristics in the attached
table. Also indicate the range of concentrations in which they are explosive.
Gas
Flammable Explosive Toxic Asphyxiating Concentration range at which it is
explosive (%)
CO
CO 2
CH 4
SO
N 2
NO x
H 2 S
H 2
Benzene
Answer
Gas
Flammable
Explosive
Toxic
Asphyxiating
Explosive limits (%)
CO
x
x
x
x
12.5–73
CO 2
x
CH 4
x
x
x
x
5–15
SO
x
N 2
x
NO x
x
H 2 S
x
x
x
x
4.3–46
H 2
x
x
x
4.1–74
Benzene
x
x
1.3–7.9
7.8.1 Explosive Limits of Mixtures of Gases or Vapours
When several substances coexist in a gaseous mixture, the explosive limits of the
mixture do not coincide with the limits of these substances separately. Even the
most conservative approach cannot be used, as the mixture can be more dangerous
than each gas separately. With this caveat, it is possible to use Chatelier’s principle