Algorithm for the lower explosion limit of mixed combustible gases entraining inert gases?

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If there are two gas streams, the first stream has a flow rate of about 300 kg/hr, with 20 vol% ethane, 5 vol% methane, 5 vol% oxygen, and the remainder being inert gases. The second stream: 2000 kg/hr of steam and negligible amounts of aldehydes. The two are mixed and then subjected to catalytic combustion. According to the specifications, the exhaust gas going into catalytic combustion must be below 25% of the lower explosive limit. How can I calculate how much air I need to add? The equipment manufacturer’s method involves determining the lower explosion limit of the mixture of the first stream of organic gases, then multiplying that value by 0.25. Finally, the amount of air that needs to be added is calculated by dividing the total amount of organic gases by 0.25 times the lower explosion limit of the mixture. I think this approach is taken as a precaution, but in reality it ignores the effect of the second stream of water vapor; therefore, the actual amount of air that needs to be added should be less. (The calculation yields approximately 3,000 cubic meters per hour of waste gas, but 8,000 cubic meters per hour of air needs to be added.) Considering that the amount of air added has a significant impact on the thermal load of catalytic combustion, I would like to ask the experts at the facility: how can we calculate the exact amount of air needed to achieve a lower explosion limit of 0.25%? Find an algorithm.