Page 387 - Advanced Mine Ventilation

356 Advanced Mine Ventilation

Based on experience, the following conclusions are made:

Less than 0.4 Normal.
0.4e1.00 Look for spontaneous combustion.
>1.00 Heating in progress.
>2.00 Serious heating.
>3.00 Fire; coal is burning.

It is by far the most reliable and most used index for the detection of spontaneous
combustion in mines.

21.2.2.3 Young’s Ratio
Again the Young’s Ratio was developed in the United Kingdom around 1924. It is
defined as follows:

CO 2
Young's Ratio ¼ (21.7)
DO 2

It is not a very reliable index because the mine always naturally produces some CO 2
and it can be dissolved in mine water.

21.2.2.4 JoneseTrickett Ratio
This index was also developed in the United Kingdom around 1955. It predicts exactly
what is burning in the mine. It is defined as follows:

CO 2 þ 0:75 CO 0:25 H 2
JoneseTrickett Ratio ¼ (21.8)
DO 2
Normally accepted interpretation of JoneseTrickett ratio is as follows:

< 0.4 Normal.
<0.5 Methane is on fire.
<1.0 Coal is on fire.
<1.5 Timber on fire.
>1.6 Not possible (check air analysis).

It is generally agreed that all these indices work well when measurements are made
in a flowing air current and not in sealed areas. There is lower limit for oxygen defi-
ciency (about 0.3%) for useful interpretation. A trend analysis of these indices often
gives a better understanding of the state of a fire in the mine.