The recirculation of hot gases (air from the sinter coolers or the cooling zone, sintering waste gases) permits energy conservation and environmental protection in sinter production. A benefit of gas recirculation is the reduced atmospheric emission of harmful materials (CO, CO 2 , H 2 S, SO 2 ) and dust. One common method of hot-gas recirculation is to return some of the waste gases from the flue to the bed over the length of the sintering machine. The gases are sent to the cover through special distributors: tubes, slots, etc. The basic measure of the efficiency of this technology is the degree of recirculation r , equal to the ratio of the bulk flow rate of recirculating gases to the cover and the total flow rate of gases through the exhaust pump. The dependence of the sintering productivity on r was studied in [1]. At first, the productivity increases with increase in r to 15%, reaching a maximum (102%) with respect to sintering in the absence of circulation, and then declines to 93% when r = 45%. The sintering productivity, estimated in terms of the sintering time, depends on the composition of the recirculating gases (the concentration of oxygen and water vapor) and also on their temperature, according to [2, 3]. These parameters, in turn, depend on r . On introducing such technology at Nippon Steel sintering plant 3 (Tobata, Japan), the degree of recirculation was chosen so as to maintain a waste-gas temperature eliminating acidic corrosion of the electrofilters: r = 25% [2]. The maximum r at which no moisture accumulates in the gases and sintering is possible is 35.5%, according to [4]. The maximum r may also be determined on the basis of the gas balance of the sintering machine’s vacuum system. The bulk gas flow rate through the exhaust unit V exh may be expressed in terms of the bulk flow rate of gases drawn through the surface of the cake V ca (nm 3 /s) where γ takes account of the increment in gases in the bed on sintering; χ takes account of the proportion of leaks through imperfections of the sintering machine V exh V caγχβt, = and its gas channel; β t is the temperature coefficient of bulk expansion of the gases. Then, in accordance with the definition adopted, the degree of recirculation r , %, may be written in the form Hence, the dependence of r on the gas-dynamic parameters of the sintering machine is obvious. Existing methods are based on a technological approach to calculating the maximum permissible r but take no account of the implementation of the technology: the design of the equipment; the sealing of the cover; or the method of delivering gases to the cover. Experience shows that these factors determine the maximum possible r with no loss of gases through existing imperfections and apertures of the cover and hence with safe operation of the sintering equipment. These aspects of the equipment are taken into account in a new model of heat and mass transfer in the cover. The model is based on analysis of the gas balance of the cover under the action of the pressure difference created by the exhaust fan and under the action of gravitational forces.