Electric Shock Drowning (ESD): A Hidden Killer
Everybody knows that electricity and water are a bad combination. Many movies have shown how the hero can thwart the evil plans of a world-wide crime syndicate by electrocuting the main bad guy as they stand in a puddle of water, probably sometime after they activated every sprinkler head in the building with a lighter. Or maybe you can relate to getting a cell phone wet, only to find the circuits short out and sensitive electronics burn up inside the phone rendering it useless. I'm sure we can all come up with a million other examples of how water and electricity don't mix. It is a universally-known fact and one that we learned from a very young age. Or did we?
The state of electricity today - in and around water
How many of us have a pool in our backyard? Or a light at the end of our dock? Or an electrically-powered boat lift? Or maybe you have a boat with a layout that more resembles the comfort of an RV with a 104" flat-screen TV in your stateroom. Many boats today have gone way beyond your grandfather's 14- foot aluminum fishing boat. I could go on about all of the places we ask for electricity without ever thinking about the hazards. But instead, I will start by asking one very important question. What dangers do we face when we put electricity near water? The two major hazards in my mind are, Shock/Electrocution and Electric Shock Drowning (ESD). Let's first talk about what these two things mean.
Electrocution and Electric Shock Drowning (ESD)
Electrocution is death by electric shock. This usually means that an electricity travels through the body on a path with sufficient current, typically somewhere between 0.1A and 0.5A, across the heart causing it to stop pumping blood. This can happen when an individual comes in contact with an energized thing (i.e. metal ladder, electrical equipment, water) and completes the circuit allowing that current to return to the source. This is the same hazard that exists on dry land as well; if you complete the path, Chances are it is going to be severe.
Electric Shock Drowning on the other hand is an entirely different animal. As the name suggests, there is a shock component of this silent killer, but no need to complete a path. What happens in this situation is that an energized component makes contact with the water because the path back to the source is often through the earth and water. This creates voltage gradients within the water and as an individual swims through this area, smaller currents interfere with the body's nervous system and cause temporary paralysis, leading to the individual being unable to stay afloat and eventually drowning. It is sometimes difficult to determine if ESD was to blame since the actual cause of death is drowning and many cases have probably gone undocumented.
If it sounds scary, it is. But there is good news. Many intelligent people are coming together to figure out ways to try and protect swimmers in the water, while at the same time support the needs of boat owners (who feel compelled to cut corners and remove safeguards designed to eliminate deaths in the water).
One measure that has proven to be successful in protecting against shock is ground-fault circuit interrupters, or GFCIs. We find these in kitchens, bathrooms, and other areas outside. The basic concept of these devices is that they monitor what goes out and what comes back and when there is a difference (meaning, the current goes somewhere else). Since that "somewhere else" could be a human body, it opens the circuit. One of the issues with GFCIs is that the trip value is set very low, between 4-6mA. This is great for protection against the type of shock that causes electrocution. But when we apply this level of protection to boats, it becomes a problem. Due to the extreme conditions that boats are subjected to, nearly every boat on the water (that utilizes shore power) today has leakage current in this range. As current leaks into the water, it lessens the further from the source it gets. So through all of the research we have found that swimmers won't be subjected to the full amount of current as they would if they were making contact with an energized component.
I used to get calls from irate boat owners who were at their wits end about how to get power to their boats. That dang GFCI just keeps tripping, they'd say! And I know that many of them waited until after the inspection and found a solution outside of what the NEC allows (if you know what I mean), which, in my opinion, is on par with letting your children make toast while taking a bath. However, while nobody would allow a child to take a bath while using a toaster, many people still bragged on social media about how they waited for the inspector to sign off and then pulled out the ground-fault protection. This just blows my mind!
Based on these issues, the result of the discussions when it comes to changes in the NEC is one of a happy medium designed to protect swimmers from ESD, and centers around this: 30mA. At this level it is not likely that enough current could pass through a person to cause the temporary paralysis that leads to ESD. However, the conversation didn't end there. For the 2017 NEC it was decided that from an installation stand point it would be best to limit any and all leakage current to 30mA. This included feeders and service level overcurrent devices. The problem is that leakage current on the service is additive, so it doesn't take long to hit that 30mA mark. For instance, a marina with 11 boats that each leak 3mA would cause this protection to jump into action even though 3mA is below the trip value set to protect us in the kitchen and bathroom. To find out how some of the conversation played out, check out my recent column in NFPA Journal magazine.
Through all of the well-intended efforts to protect us around new installations, you're probably asking, "But what about my marina that was built in 1984?" And here is where we run into issues. There are many existing marinas and docking facilities where none of these precautions have been taken, so how do we handle those? Well, this is where we need your help. This is where we need to educate people across the country about why it is so dangerous to jump in the water in these areas. Check out NFPA's video below on
So I hope this helps shed some light around these silent killers lurking in the water and I encourage all of us to do our part to foster discussions in our communities about safety in the water. The along with the