It was a year ago today that Brendan Nappier fell victim to a silent deadly gas known as carbon monoxide. I knew him less than 24 hours, but in that short time he seemed like a really nice guy and I could see a long term friendship forming. He had arrived the day before in Cozumel for a week of cave diving and exploration. About a dozen of us had been there for several days and had already made some dives in Cocodrilo, Aerolito, and Dos Coronas. A few others flew in the same day as Brendan. The group broke up into 3 teams. After gathering our tanks for the day, 5 of us headed over to Cocodrilo. As we were setting up for our dive we were joking about the condition of the o-rings in the yoke valves as we replaced them.
The plan was to head back to the Air Dome Room, surface, have a snack and drink which we had stashed in pockets, and take some photos and video. Two of the team were diving SCRs with nitrox bottles as drive gas and the other 3 were diving OC. It is a fairly long swim to the Air Dome Room. We planned about 70 minutes to get there with an average depth in the 20-30 foot range. We had placed 3 safety bottles in the system the previous couple of days in preparation for this dive. A couple of us were also carrying additional stage bottles to be used as safeties rather than actual stages due to the long swim. We discussed the plan and stressed keeping a nice slow pace due to the size of the team. The cave passage is large and can handle many more so that wasn’t a concern. The team order was Brendan in the lead, Jose (a local diver on the island) second, Michael Angelo third, followed by me and Jen.
About 15 minutes into the dive the plan suddenly changed. Jen and I noticed Brendan, Jose, and Michael Angelo speed up their pace. I looked over at Jen and we continued our pace figuring they would either realize we were falling behind or we would eventually meet them in the Air Dome Room. They went around a corner and a few seconds later we reached them and saw something was very wrong. Brendan was vertical in the passage. As we got closer we noticed he didn’t have a regulator in his mouth. Jose and Michael Angelo were already with Brendan and pushing a regulator into his mouth. We sped up to assist. I remember thinking the sudden increase in speed must have caused a buildup in carbon DI-oxide and he must have blacked out. I scanned the ceiling hoping to find an air pocket we could bring him to and try to revive him. But we had no such luck.
I remember clipping the long hose regulator belonging to Brendan to the line as we got situated around him to pull him out. I didn’t want to compound the problem by losing the line. Once we got situated I unclipped the reg and we began our exit. In total, the reg was clipped to the line for less than 10 seconds. Jen saw us dealing with Brendan and decided to swim ahead lighting up the line for us so we could focus on Brendan. I focused on pulling Brendan out while Jose and MA took turns holding the regulator in his mouth while purging it. I glanced at the line every now and then only because we had just surveyed this passage the day before and I knew the line from the entrance to about 400’ was not knotted. Once I saw the knots were gone I just focused on following Jen’s light.
Having been in the healthcare field for over 20 years I pretty much knew it was hopeless at this point but I also knew I couldn’t leave Brendan’s body in the cave. We managed to get out of the cave about 5 minutes faster than the swim in. We surfaced and immediately continued resuscitation efforts just in case there was any amount of hope left. There wasn’t.
The rest of the day is a blur. I know one of the other teams showed up and gathered gear for us. The staff at the resort where the system entrance is located got us water and towels. The local police showed up. The third team finally showed up. The police eventually finished their questioning and we headed back to the house. We kept going through the dive trying to figure out what went wrong. Eventually someone mentioned Brendan’s rebreather was not flooded and I recalled squeezing the counterlung to purge some air out of it as it was expanding when we ascended. Brendan had enough sense during his last moments to know something was wrong and had bailed out.
What we didn’t know until the next day was that it wasn’t carbon DI-oxide that killed Brendan that day. It was carbon MON-oxide that did it. The autopsy revealed lethal levels of carbon monoxide in Brendan’s blood. There is no way he could have survived, even if there had been an air pocket right there. Hemoglobin has an affinity for carbon monoxide that is over 200 times that of oxygen. Once the carbon monoxide binds to the hemoglobin it is not easy to break that bind.
So what did we learn that day? We learned that we must always analyze the gas we are going to breathe underwater, not only for oxygen content and helium content but also for carbon monoxide. While carbon monoxide is not that commonly found, when it is there it can kill. Everyone on our team now owns a carbon monoxide analyzer and analyzes every single scuba tank we breathe from regardless of where the tank was filled. We even analyze oxygen tanks. Someone we know found 17 ppm carbon monoxide in a 100% oxygen decompression cylinder. Yeah, we’re still wondering how it got there too.
No one is immune to carbon monoxide. It can be lethal in your house (if you don’t have a carbon monoxide sensor in your house buy one). It will be lethal underwater. We have found several cases of carbon monoxide poisoning over the past 10 years in simple searches on the internet. Not all have resulted in death. Sometimes the combination of quantity and depth work in the diver’s favor. But all have resulted in illness enough to cause dives to be aborted, not only for the moment but for the day or trip. We even thought of some of our own dives in which there were unexplained things that now indicate we could have had carbon monoxide in our breathing gas. We’ll never know.
Carbon monoxide analyzers can be purchased for about $300. The sensor will last the average diver close to 4 years. A replacement sensor costs about $140. So for an initial cost of $75/year and then another $35/year you can have the peace of mind of knowing you do not have carbon monoxide in your breathing gas. Don’t trust your fill station. I have my own fill station and I don’t trust it. Yes, there are inline carbon monoxide analyzers on some compressor systems. However, unless there is a kill switch wired in to shut the compressor off if the analyzer alarms or someone is standing there watching the analyzer the entire time the compressor is on you cannot guarantee there is no carbon monoxide in that gas. This isn’t something that once it starts will continue so that you can walk away from the analyzer and check it later. A vehicle could drive up and exhaust could be drawn into the compressor intake for a few moments. Or the compressor could be running hot and inactivate the hopcalite in the filters so the carbon monoxide is not converted into carbon dioxide. This might also only last for a few moments.
So, on this one year anniversary of Brendan Nappier’s death I ask that if you haven’t yet purchased a carbon monoxide analyzer that you please reconsider. It’s a small price to pay for your life. If you only dive a few times a year and don’t think it’s worth it, there are companies that rent carbon monoxide analyzers by the week. For about $10/week you get the benefits without the annual upkeep. Whatever way you decide, just make sure you analyze your gas each time, every time.
