Using mineral oil based petroleum lubricants with Nitrox compressors has too much potential for carbon monoxide contamination due to their relatively low flash point temperatures in the 100°C range. So when the dive industry started compressing Nitrox, polyalphaolefins with higher flash point temperatures over 200°C became the de facto recommendation for lubricating Nitrox compressors.
Today, PAO lubricant performance in compressors is surpassed by the synthetic ester based high-performance lubricants. Esters have a similar flash-point temperature range and, also like PAOs, there is no published data available as to how esters perform in Nitrox compressors. Lubrication professionals (called tribologists) we have consulted are of the opinion that if PAO lubricants are good with Nitrox then ester base lubricants are better; given their excellent performance in higher temperature applications with superior oxidation stability that resists formation of varnishes and carbon deposits.