No carbon dioxide, methane or carbon monoxide was found. Normal air is 78 percent nitrogen, 21 percent oxygen and smaller percentages of other gasses, the city said.
Three Middletown firefighters were also overcome as they attempted to rescue Lakes at the scene on Yankee Road. All three have been released from hospitals and are recuperating.
Witnesses said Lakes, 31, was kneeling just outside the manhole when he was overcome and fell into it, said Middletown Law Director Les Landen. He was wiping off the edge of the sewer, preparing for the insertion of a remote camera as part of a routine check. When witnesses looked a moment later, he was gone, Landen said.
According to experts, sewer workers can be overcome by gases without entering the confined space. That happens when a plume of gas erupts from the sewer when the manhole cover is lifted . The invisible gas can shoot upward like liquid from a shaken can of soda, said Irv Gemora, executive director of the National Association of Sewer Service Companies in Owings Mills, Md.
Paul Jennewine, medical director for the Middletown Health Department, said that a lack of oxygen, coupled with high levels of nitrogen, could quickly lead to asphyxiation.
In just two or three breaths over about 15 seconds, a person would become disoriented, he said. The person would be unable to function and lose consciousness in less than a minute. Within just a few minutes, brain function, breathing and heart action would stop, Jennewine said.
Testing was to begin Friday night to locate the possible source of the nitrogen in the area of the sewer cavity. Some oxygen depravation was discovered in a nearby AT&T trench line. As a precautionary measure, the conduit is being ventilated.
City Manager Judy Gilleland said, “Now that we know the element involved, we can move on to identifying the source and stop the flow of the nitrogen into the sewer area. We are now moving from the identification phase to the remediation and mitigation stages.“
Landen said that “while data we have on hand is consistent with nitrogen asphyxiation, it is up to the Butler County Coroner’s office to determine the actual cause of death. Their toxicology reports may shed light on the cause.”
Middletown’s report on the incident cited a U. S. Chemical Safety and Hazard Investigation Board Safety Bulletin that said “nitrogen is not a poison in the traditional sense. It presents a hazard when it displaces oxygen making the atmosphere hazardous to humans. Breathing an oxygen deficient atmosphere can have serious and immediate effects. The exposed person has no warning and cannot sense that the oxygen level is too low.”
Lakes was buried Thursday.
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