Air quality on aircraft in flight has been studied extensively. Most studies indicate that the current recommendations for air quality on the flight deck and in passenger cabins of aircraft are of low risk providing that relevant legislation is complied with, relevant airworthiness standards are met, and relevant engineering and operational systems function properly. However, where problems arise, and aviation fluids such as hydraulic fluids or jet oils pass to the environment where air crew or passengers are found, the potential exists for adverse exposures to occur, and for adverse health problems to arise. Evidence is available to suggest that the number of exposure events is not small. However, most studies that have been carried out to measure atmospheric contamination in aircraft by engine oil leaks or hydraulic fluids are sufficiently flawed on procedural and methodological grounds as to render their conclusions invalid. Problems include: studies that were conducted on the ground, studies that were that were conducted in the absence of an exposure event, such as an oil leak studies that use the wrong sampling techniques, studies that measure the wrong contaminants, analytical techniques with poor limits of detection, poor chain of custody and the like. This has not stopped inappropriate use of such studies, or inappropriate conclusions being drawn from them. There is a real need for monitoring the cabin environment during exposure events, so that a suitable understanding of levels, toxicity and impact of chemical exposures can be established.