NTSB Carbon Monoxide Debate

A December 20, 2021, recommendation by the National Transportation Safety Board to the FAA has some debating the merits of making electronic carbon monoxide detectors a requirement in light aircraft. Citing 31 reports of fatal accidents since 1982 and evidence that the widely accepted “spot” detectors may be ineffective, the NTSB strengthened its recommendation that the FAA require alerting detectors—built to a common standard—for general aviation aircraft with enclosed cabins.

Carbon monoxide is a well-known toxic byproduct of reciprocating engines that must be completely vented to the atmosphere to avoid endangering aircraft occupants. Often called a “silent killer,” carbon monoxide is odorless and tasteless, and the onset of symptoms can hinder a pilot’s ability to recognize them. If an aircraft’s exhaust system or cabin heater develop a leak, carbon monoxide may enter the cabin and overwhelm the occupants in a matter of minutes.

The NTSB made similar suggestions to the FAA in 2004, and the new recommendation bolsters the Board’s position with additional studies of fatal accident reports and service difficulty reports. Notably, they suggest lethal exhaust system failures may be overlooked by maintenance personnel and may occur earlier than the FAA’s current 1,000-hour inspection and muffler-replacement recommendation. In citing the 2019 fatal accident of a Cessna 150, the Board noted one of the airplane’s two mufflers had only accumulated 742.9 hours yet displayed corrosion, thinning of the walls and pin holes.

Participants in The Aviator’s Lounge group on Facebook expressed a range of responses to the NTSB recommendation. “Am I the only one who thinks the NTSB is trying to fix a problem that doesn’t exist?” posted one user. “This is a poor maintenance issue,” posted another who added, “Checking exhausts during an annual [inspection] should catch muffler defects.” Others leaned in favor of alerting detectors, including a firefighter who posted, “I agree that they should be mandated in houses and aircraft.”

In its recommendation, the NTSB emphasized that any future requirement for detectors should specify Technical Standard Order (TSO) C48, “Carbon Monoxide Detector Instruments,” and encouraged the EAA and AOPA to issue their own recommendations to members regarding the use of detectors.