A positive σ indicates increasing the rate of reaction increases the result of interest and a negative sensitivity indicates increasing the rate decreases the result. If CH 4 conversion through the reactor was less than 1 × 10 -8 mol m -1 , all CH 4 and O 2 conversions, yields, and selectivities through the PFR were rounded down to 1 × 10 -15 mol m -1 (approximately 0, to avoid zero division errors), as the overall reaction was negligible. If a reaction was not found in a microkinetic model (because RMG decided it was not important enough to be included) its sensitivity was set to 0.