Page 415 - Advanced Mine Ventilation

384 Advanced Mine Ventilation

Figure 23.4 Temporal and spatial characterization of various ignition sources.

very low, and the temperature is also low. Here one should be more concerned about
the ignition temperature.

23.1.3.1 Minimum Ignition Energy

Minimum ignition energy (MIE) for typical mine gases for both air and oxygen envi-
ronments is shown in Table 23.3.
Generally speaking, all hydrocarbons have an MIE of 0.25 mJ. The MIE is lower by
at least an order of magnitude for oxygen environments. Confining pressures greatly
change MIE for oxygen environments.

23.1.3.2 Ignition Temperatures

Ignition temperature is a more important factor when a large vessel is the source of
ignition. The minimum autoignition temperature (AIT) of gases is used for designing
such vessels. Table 23.4 shows the AIT for typical mine gases in air and oxygen
atmosphere.