The smoke and air flow through an opening in case of fire is analyzed by the treatment of a sluice flow. However the method to treat the smoke and air flow is different in the point of the considerations of the density difference between smoke and air and the pressure varying on the interface. This method shows the following results; 1) This method shows the clear stream line of the air flow, and is able to consider the curvature of stream line when the air is static. This method gives the hyperbolic velocity distribution on an opening. 2) This method shows the existence of the maximum value of the flow rate through an opening. The characteristic flow around the bound of the maximum value is verified by the experiment. 3) The burning rate expected by the maximum air inflow rate describes analytically the empirical relation between the air inflow factor and the burning rate.
