Page 413 - Advanced Mine Ventilation

382 Advanced Mine Ventilation

Figure 23.3 Flammability for methaneehydrogenecarbon monoxideenitrogenecarbon
dioxideeair mixtures (example).

Max Oxygen Concentration ¼ 5 þ 7R (23.5)

In the above examples, R ¼ 0.55; this allows the maximum O 2 concentration to be
8.85% but the actual oxygen is only 8%. Hence the mixture is nonexplosive/
nonflammable.
Table 23.2 shows the upper and lower limits of flammability for gases generally
found in coal mines. Minimum oxygen concentrations for combustion are also shown.

All numbers are for standard pressure (1 atm) and temperature (60 F).
If the flammability limits of the components of a mixture are known, the limit of
flammability for the mixture can be calculated using Le Chatelier’s law [6]. The lower
limit of flammability for the mixture, L, is given by Eq. (23.6).