An Analysis of Cabin Ozone Regulations

Exposure to elevated levels of ozone have been reported to be associated with complaints of discomfort such as dry mouth, eye irritation and dryness, nasal irritation coughing, and headaches.  The Federal Aviation Administration (FAA) established regulatory requirements in 1980 to limit cabin ozone levels to no more than 0.25 parts per million (ppm) at any time or 0.1 ppm averaged over a 3-hour interval for any flight over four hours in length.  The FAA also published an Advisory Circular (AC), AC 120-38, to provide guidance to air carriers on how to comply with these then new ozone regulations. Methods of compliance include the use of catalytic converters, or ozone filters, designed to remove ozone, utilizing statistical methods to prove that ozone concentrations will not exceed limits for the carrier’s route structure and flight planning to avoid areas of reported high concentrations of ozone. The calculations used to determine cabin ozone concentration from manufacturer’s filter efficiency data and ozone levels are to be based on published ozonesonde data found in the AC 120-38 or an equivalent data set.  Unfortunately, the published ozonesonde data in the AC 120-38 are outdated and the AC does not point to any other data source that is acceptable to the FAA to conduct the required statistical analysis. In addition, once compliance is shown, no follow-up measurements are required to ensure that ozone levels remain below these required levels.  Actual ozone concentrations have been measured in the aircraft by several researchers that exceed these regulatory levels. Finally, FAA ozone regulations and AC 120-38 do not address cumulative effects of ozone exposure to crewmembers over multiple flights and do not offer any protection against ozone exposure for crewmembers on non-passenger carrying flights. A revision of federal regulations to afford protection to all crewmembers, account for cumulative effects, and updated compliance methods that rely on current ozonesonde data and periodic ozone monitoring should be accomplished to ensure crewmembers are not subjected to ozone levels that could potentially result in serious health concerns.