The method of evaluation of the approximate temperature of arising spontaneous fire centre and time of coal self-ignition is presented in this paper. The method uses Bystron's (1997) model of coal self-heating and measurement of carbon monoxide concentration in the mine air outside the fire centre. Knowledge of the spontaneous fire centre temperature and time of fire beginning allows for more accurate analysis of the fire hazard in the coal mine and allows for adequate time to undertake special fire prevention actions. The method is illustrated by an example from Polish mining practice.