Rescue operations during mine fires or methane explosions are highly dangerous for rescue workers. The knowledge of the composition of the coal mine atmosphere and the calculations of its explosibility may help to increase the safety of the rescuers. In the Czech Republic, a system called "Mine Gas Laboratory" (DPL) has been used for these purposes. The DPL allows measurement of the composition of the mine atmosphere and transmits the data necessary for evaluation to the surface. Up to now the explosibility evaluation of the coal mine atmosphere has depended either on the rescuers' experience or on software code calculation. The code called "Vybuchovy trojuhelnik" (explosion triangle) is a graphical computing system intended for fast assessment of explosibility of fuel-air mixture. This article introduces the code and describes two simple methods of explosibility evaluation. The first method is "explosion triangle analysis"-a graphical method based on empirical graphs transformed into equations. The second method uses thermodynamic calculation based on chemical balance dynamics and Gibbs and Helmholtz energy. According to the requirements of the Czech Bureau of Mining (CBU) and Central Mine Rescue Service (HBZS), the code solves the problems of explosion triangle for both standard and nonstandard coal mine atmosphere compositions. Unfortunately, the atmosphere composition must be introduced manually due to the unknown format of the data transmitted from the old DPL model. On I September 2005, a project started to develop a new system for on-line monitoring and atmosphere explosibility evaluation. The system should be able to measure CO2, O-2, CH4, H-2 and CO concentrations as well as the wind speed, temperature and humidity. The "Vybuchovy trojuhelnik" code will be used as a basis for explosibility evaluation, and an on-line connection with the new model of DPL will be established. (C) 2007 Elsevier Ltd. All rights reserved.