通过分析炉内废气循环过程的特点，在一定废气循环量的条件下，建立了炉内废气容积流量与废气循环次数的定量数学关系，建立了废气中氧气浓度与循环次数的定量数学关系。运用数学极限定律，得出氧的极限浓度定量数学公式，以此为基础，建立了助燃剂中氧气的浓度以及可燃混合物中氧气的浓度定量数学关系式。并以此推导出其他成分浓度的计算数学模型，为实际生产过程中不同环节的气体成分检测、分析建立了基础。

By analyzing the feature of the process for the recycled waste gas in furnace, let the volume of waste circulation be constant, the guantitative mathematical relations between the volume flow of waste gas and the recycled times of waste gas which goes into combustion-supporting air in furnace were built, and the quantitative mathematical relations between the density of oxygen in waste gas and the recycled times were built. By using the limit mathematic law, the quantitative mathematical formulation of the limit density of oxygen was gotten. On the basis of this, the quantitative mathematical formulations of oxygen density in combustion-supporting air and in flammable mixture were built. By using the similar methods, the mathematical calculating formulations of the density for other compositions were inferred. It provides the base for checking and analyzing the gas composition at different stages in real production process.