The firing machines of OK-310M type have been modernized at Lebedinskij Ore-Mining and Processing Enterprise. Reversing of the cooling agent in the cooling zone has been eliminated. Scheme of gas - air flows has been varied. At the present, 'Lebedinskij GOK' open-end joint stock company operates the modernized machines. Productivity of the machines has been improved. been reduced. However, analysis of temperature stresses has not been performed. Total heat-engineering examination of units of the firing machine is necessary. Then, further modernization of the machines can be performed. Ecological safety can be provided in this case.