Pentane, an organic compound, an indicator of lipid peroxidation. Its normal concentration in the breath of healthy humans is lower than 10 pmoles/l. Breath pentane, which is produced by reactive oxygen species-mediated lipid peroxidation of n-6 polyunsaturated membrane fatty acids, is a marker of oxidative stress. Experiments on animals have shown that the breath pentane analysis could provide early, rapid, noninvasive and continuous assessment of lipid peroxidation during hepatic ischemia-reperfusion injury.