The lag time for the O2 indicator to visually complete the color change from purple to pinkwas 3e5 h following the lag time for the OS to decrease headspace O2 to below 0.01%. The O2 sensor used in this experiment is based on the reversible redox reaction of methylene blue which takes a longer period to reveal background pink after the O2 level decreases below 0.01%. The sensor turned purple almost instantly upon cutting the bags open for sampling. Reducing methylene blue to colorless leucomethylene blue takes longer than oxidizing methylene blue back to its blue form (less than 5 min) in the presence of O2.