Disaster expert weighs in on possible causes of Monday’s tragedy

Miami-Dade Fire Rescue hazmat teams discovered hydrogen sulfide and methane inside the Key Largo stormwater drainage hole where three contracted utility workers were killed Monday and a firefighter was seriously sickened.

Both gases displace valuable oxygen, creating a dangerous environment, but it’s the hydrogen sulfide that’s poisonous, said Neil Lipski, a retired Milwaukee, Wis., deputy fire chief who has been investigating deadly gas accidents as a firefighter and since forming the renowned National Tunnel Institute in 1982.

“Methane’s not poisonous,” he said. “You can breath in it, you can talk in it. Methane would just replace the oxygen.”

In a non-ventilated hole like the one in which the D.N. Higgins workers died on Long Key Road Jan. 16, that alone could be a quick killer. Add to that the hydrogen sulfide, however, and the situation gets deadlier, faster.

Hydrogen sulfide is heavier than air and travels in water. The first worker to climb down the hole on Monday could have released enough hydrogen sulfide that was contained in the standing water at the bottom of the 15-foot hole to instantly make the air surrounding him in that confined space lethal, Lipski said.

“If he trampled in the water, there could have been a high enough concentration released to kill himself,” he said.

One of the deadliest tricks gases like hydrogen sulfide and carbon monoxide can play on people is pretending they’re not there, Lipski said. While carbon monoxide kills people because it’s odorless, hydrogen sulfide is so pungent that after a time, people become desensitized to it and think it dissipated.

“The problem with hydrogen sulfide is that as it increases in volume, our olfactory receptors negate it,” said Lipski. “You think the odor has gone away and the gas has gone, but it didn’t.”

But the oxygen deprivation can’t be downplayed as a possible culprit in the men’s deaths, Lipski said. “We don’t know for sure,” he said. “That will all come out in the coroner’s report.”

Federal working standards require a space to have 19.5 percent oxygen by volume.

“Anything below that, you can’t have people working in that space,” Lipski said. “You have to take steps to increase it.”

And gases like methane in tight spaces can rapidly displace oxygen, creating perilous confined surroundings.

“Let’s just say at some point it’s 20 percent methane,” Lipski said. “It comes in and pushes out the oxygen.”

The deaths of the D.N. Higgins workers and the hospitalization of Key Largo volunteer firefighter Leonardo Morena, who entered the hole to save the men, are being investigated by the Monroe County Sheriff’s Office and the federal Occupational Safety and Health Administration. Until those investigations conclude, there will be much speculation on what led to the tragedy. But what is clear, Lipski said, is every man who entered the hole should have been wearing a self-contained breathing apparatus, which none of them were.

“You can’t just win this,” he said. “It just doesn’t work. You can’t just run in there.

This story was originally published January 20, 2017 at 10:32 AM with the headline "Disaster expert weighs in on possible causes of Monday’s tragedy."