To prevent corrosion, tri-cresyl-phosphate (TCP) is added to aircraft engine oil. TCP occurs in a mixture of ten different isomers. The ortho isomers of TCP are known to be the most neurotoxic, however at present it is unknown in what concentration the ortho and the other isomers occur in cabin air, due to leakage in the air conditioning system, and in engine exhaust fumes. Various professions of airline staff may be exposed to concentrations of TCP. This research describes the assessment of the exposure through measurements inside the cockpit during flight, spot measurements on the ramp and personal measurements of ground mechanics.

ASHRAE Standard 161, Air Quality within Commercial Aircraft, includes a requirement for bleed air sensors to detect contamination from lubricating oil. One potential approach to meeting this requirement is through particle detection. A four-part experimental program was conducted to develop a detailed characterization of particles that result when bleed air is contaminated with lubricating oil. This research shows that development of sensors for detecting oil contamination in aircraft bleed air should focus on ultrafine particle detection and sensing of low contamination levels may require sensitivity to extreme ultrafine particles 10 nanometers and smaller.

The outside air used to pressurize and ventilate the cabin during flight is supplied by bleed air from the propulsion engine compressors on most airliners. The potential for this air to be contaminated by lubricating oil from leaking engine seals and other sources is believed to be rare. ASHRAE Standard 161, Air Quality within Commercial Aircraft, addresses this issue and includes a requirement for bleed air oil contamination sensing. This standard does not address the technology to be used for this sensing nor does it provide guidance about the physical characteristics of the contaminants as they appear in the bleed air.