Why hadn’t Billy and Tim been able to sense the danger they were in? McCauley knew the absence of the in-line analyzer was only part of the answer. Riggs told her about how he had asked Harald what to do with the MAP Mix 9000’s AC electrical cord, and how Harald had instructed him to keep it coiled up with its factory-issued twist tie. By now, McCauley understood that although the mixer didn’t need any electricity or battery power to function, its built-in pressure alarm did need an external power source. That’s what the AC power cord was for. McCauley learned that this built-in alarm would not have measured the oxygen content of the breathing air, but it would have provided a critical warning to the divers that the pressure coming from either the liquid oxygen or liquid nitrogen had fallen below safe levels. Despite the tunnel’s lack of electricity, the alarm could have been powered by a battery. McCauley couldn’t get over the fact that the damn alarm was simply left unplugged.
Without either an in-line analyzer or a functioning pressure alarm, the divers were forced to rely on the patently ridiculous protocol of using the handheld monitor to test the blended breathing air and hoping that the ambient air mixing with the sample didn’t throw off the measurements too much. Harald’s response to Riggs’s request for an in-line analyzer—namely, to give the divers one additional but equally unreliable handheld device—had been no solution at all. This shoddy measurement system had masked the deepening trouble to the point where the divers’ first warning sign hadn’t come until DJ and Riggs blacked out at the end of the tunnel. McCauley now understood why those two divers had been affected before the others. They were engaged in the most physical exertion, huffing and puffing as they lugged equipment and crawled into narrow pipes. McCauley referred to the chart on the effects of reduced oxygen levels that the navy doctor had included in her report.
12-15 percent: Breathing increases, especially in exertion, pulse increases, impaired coordination, perception and judgment
Given their strenuous work, DJ and Riggs had been like tennis players at the end of a long, grueling match, breathing more strenuously to suck in the extra oxygen their bodies were craving. Billy and Tim, meanwhile, were just sitting inside a vehicle, waiting. Although they were beginning to suffer the effects of oxygen deficiency, in light of their sedentary situation in the dark, it would have likely presented itself, at least initially, as barely detectible fogginess.
10-12 percent: Breathing further increases in rate and depth, poor coordination and judgment.
Hoss’s exertion level fell somewhere between the other two pairs of divers. And when he called Tim with an urgent request to check the oxygen reading, that plea appeared to have briefly snapped Tim and Billy out of their fog: “Shit, it’s 8.9!”
Again, the chart:
8-10 percent: Mental failure, fainting, unconsciousness, nausea
The navy report noted that the 8.9 percent oxygen level Tim relayed to Hoss must have continued to drop until Tim and Billy’s deaths. It also contained the answer to another mystery, the same one that had puzzled McCauley from the start: If all five divers were breathing off the same supply of mixed liquid gas, why did only Billy and Tim die? Clearly, Hoss had saved the lives of the excursion crew by switching their air supply to the HP tank on the boat. But as it turned out, they had more of a cushion.
It all came down to geography. When the weakening oxygen regulator finally froze over, turning the breathing air into something that was mostly if not entirely nitrogen, proximity became Billy and Tim’s enemy. That toxic hot shot of nitrogen had to travel up to fifteen hundred feet to get to the manifold in the excursion crew’s boat and then out to the facemasks of Hoss, DJ, and Riggs. To get to Billy and Tim, however, it had to travel just ten feet.
If each of those findings had answered an important question that had been weighing on the detective’s mind, a pair of related revelations blew her away. The first came from Tim Reading, the safety manager for Airgas Northeast, the company whose New Hampshire facility had supplied Harald with the gas used on the job. He insisted to McCauley297 that neither Harald nor anyone at his equipment supplier A-L back in Spokane had ever informed Airgas that the tanks of liquid oxygen and liquid nitrogen would be used as breathing air for human beings. Reading said company policy and industry practice prohibited both the blending of gases for human consumption and the sale of liquid gases for that purpose. The risks were simply too high.
The more shocking discovery had to do with the MAP Mix 9000 itself. In her attempt to understand why the mixer had failed to do its job, McCauley wasn’t content to talk simply with Tony Drybanski, the salesman-president of the mixer’s local distributor. She also persuaded the mixer’s manufacturer, PBI Dansensor in Denmark, to send one of its top engineers to meet with her on Deer Island. Immediately upon inspecting the MAP Mix 9000 on site, that engineer, Steen Hansen, made it clear how distressed he was.
Through his thick Danish accent, he explained that the mixer’s cover had been removed and its factory-set pressure settings had been changed. Even though Harald had done this in consultation with Drybanski, the Danish engineer now said it never should have been tampered with. That’s why there was a warning in bold type right there on the first page of the mixer owner’s manuaclass="underline" “Important: MAP Mix 9000 should be opened by authorised personnel only298”
That led Hansen to deliver a bombshell299 about the device. The MAP Mix 9000 should never have been used for the divers—or for any human beings. The owner’s manual specified that it was intended for “industrial uses,” and the Danish engineer gave McCauley examples of what that meant: packaging meat and cheese and burritos, to give them a sort of vacuum seal that would lead to longer shelf life. The mixer was not to be used to blend breathing air.
Hansen said he and his colleagues300 never thought anyone would be stupid enough to use the mixer for such a high-wire act. (Only after the accident would his company add a new warning label to the mixers that read: “!!Danger!! Do NOT use this equipment for air supply for human beings.”) The unit had a margin of error of plus or minus 2 percentage points, which might be fine when packaging burritos in plastic containers but was clearly inadequate for trying to keep a team of five divers alive in a moonlike environment under the ocean. When the MAP Mix 9000 was used in food packaging, the Danish engineer said, its built-in pressure alarm was usually hooked up directly to the packaging machine. That way if the pressure dropped on one of the gases as it was being blended, the packaging machine would automatically shut down. Hansen said that even though the mixer should have never been used to supply the divers with air, Billy and Tim would likely still be alive if Harald had taken the simple step of energizing the pressure alarm. Instead, he had instructed Riggs to tie up the device’s electrical cord and forget about it. Although there were no working electrical outlets in the tunnel, Steen said, it would have been easy to hook up a twenty-four-volt battery to power the alarm and then arrange for the HP air backup supply to kick in automatically if the pressure dropped.
297 (Chapter 14, note 18)
He insisted to McCauley: Timothy Reading to Mary McCauley, July 30, 1999.
299 (Chapter 14, note 20)
That led Hansen to deliver a bombshelclass="underline" Trooper Mary McCauley, “Interview of PBI-Dansensor Representatives in Reference to Tunnel Death Investigation at Deer Island,” Massachusetts State Police Suffolk County Detective Unit, October 9, 1999, 10.
300 (Chapter 14, note 21)
Hansen said he and his colleagues: Steen Hansen, interview by author, June 2011. Hansen confirmed what he had told Mary McCauley: that it was inconceivable to them that anyone would have ever used the device for human breathing air. During a tour of the PBI Dansensor plant in Ringsted, Denmark, he showed me the warning labels that were added to the devices as a result of the tunnel deaths.