At the end of January 2017, six young people died in a summerhouse in Arnstein, Bavaria. The deadly power generator operating in the hut was neither old nor defective. In its cylinder, air containing 78 per cent nitrogen and almost exactly 21 per cent oxygen burned together with a petrol mixture to produce an exhaust gas consisting of around two thirds nitrogen, carbon dioxide, water and up to ten per cent carbon monoxide (CO). This relatively low proportion of the gas fatally poisoned all six young people.
The case attracted a great deal of attention and sympathy. However, carbon monoxide poisoning is a common occurrence. In fact, according to statistics, around 200 people have died from this dangerous gas every year in recent decades.
The trend has been rising again for several years. In each of these accidents, the concentration of carbon monoxide in the blood of those affected rose to too high a level until they felt tired, dizzy or nauseous. What are often mistaken for symptoms of illness are actually the initial effects of inhaled carbon monoxide.
This can also happen quickly in a cramped cabin or even under a reasonably closed boat cover, as boats are not only watertight but also largely airtight. The motorboat accident in 2015 in Waren on the Mecklenburg Lake District has parallels with the current accident in Bavaria:
Four secondary school students aged between 17 and 19 celebrated their last day of school before their final exams on the "Frau Klein", a traditional steel motor cruiser around ten metres long with a closed wheelhouse, moored at the jetty.
Two of the pupils died of carbon monoxide poisoning, the other two were rescued with serious injuries. According to the public prosecutor's office, the gas system was defective. In addition, there was already a high risk of explosion due to the gases released, which could have been fatal for the rescuers.
The circumstances that led to the poisoning on board the "Mrs Klein" were possibly similar to those on board a motorboat in Bremerhaven. The couple only narrowly escaped death. Until the very end, they had not realised the deadly danger that was spreading in the cabin while they slept.
In terms of evolutionary history, carbon monoxide is a threat that has only recently emerged and for which humans have not yet developed an awareness.
Guido Kaiser conducts research at the Poison Information Centre at Göttingen University Hospital and entitled one of his publications: "A brief history of CO poisoning". It describes how people can neither taste, see nor smell the gas.
After inhalation, it binds to the red blood pigment haemoglobin in the bloodstream and occupies - with 325 times more binding force! - the place that is actually intended for the vital transport of oxygen. Symptoms such as exhaustion, headaches, nausea or dizziness are often so unspecific that CO poisoning is often not recognised straight away.
"Animals don't have this ability either," adds Axel Hahn, retired risk assessor and ship's doctor on the "Alexander von Humboldt II". "In humans, the typical reddening of the face is often misjudged as redness caused by sun, wind or alcohol; even doctors have problems making a diagnosis without additional aids such as a so-called Hb-CO determination."
The two spouses on board their motor yacht in Bremerhaven's New Harbour also noticed such signs. They narrowly escaped a fatal poisoning in their sleep last June. "The owner is a handyman and replaced his previous refrigerator on board himself.
He used a camping model that can be operated with 230 volts and 12 volts as well as with gas," says Michael Herfort from the Bremen water police, describing the background. As required for such an installation, the owner also carried out a pressure test on the self-installed gas pipe and tested it with leak spray.
However, the system was not approved - a mistake with serious consequences, as an inspector would have realised that such a refrigerator may only be installed in camping vehicles. The air required for combustion in gas mode must be drawn in from outside. The owner had not considered this; a hole would have had to be drilled in the hull anyway.
On the night of Sunday to Monday, 6 June 2016, the refrigerator was operated with gas for the first time. "At 5 o'clock in the morning, the wife used the on-board toilet, which still had a porthole open. She collapsed, the noise woke up her husband - who felt completely exhausted - and suspected a heart problem," Herfort continues.
"That's why he took them down the companionway to the fresh air in the cockpit - in hindsight, that probably saved them both." Because throughout the night, the refrigerator had consumed most of the oxygen in the cabin.
The lack of oxygen led to incomplete combustion with an increasing proportion of carbon monoxide in the combustion exhaust air. The firefighters, who were immediately called out, measured 190 ppm (parts per million) in the now ventilated cabin using the CO detectors they routinely carry with them. The couple were taken to a neighbouring hospital for observation.
So the question naturally arises as to whether the gas cooker in the galley, despite its high output, does not lead to the same problem: Theoretically, such a situation is just as conceivable. In practice, however, there are numerous circumstances that speak against it: Firstly, the hob is usually located in an easily ventilated area; simply because of the heat and the moisture generated, a draught is usually provided anyway. In addition, cooking hardly takes hours and there is always someone around.
However, the cooker must not be used for heating. In 2014, two 21 and 26-year-old fishermen died in the bunks of their 10-metre boat, which was moored at the quayside in Whitby (North Yorkshire). They had left their gas cooker on overnight as a source of heat.
This and similar cases were used in the UK as an opportunity to draw attention to the danger of CO poisoning on boats throughout the country, and the British Marine Accident Investigation Branch (MAIB) issued a corresponding warning.
Nevertheless, a couple and their dog died on board the 15-year-old Doral 250 SE "Love for Lydia" last August. The motor yacht was moored alongside and the engine was running at high idle speed - presumably to charge the batteries.
A light aft wind drove the exhaust fumes from the stern first under the canopy and then into the unventilated cabin. During a reconstruction of the accident, a high concentration of carbon monoxide could be measured within three minutes in this way.
It was probably a petrol engine, as it is generally accepted that the proportion of carbon monoxide emitted by diesel engines should be less than 0.1 percent. In the case of newer car engines up to today's strictest Euro 6 emissions standard, only slightly higher values are to be expected in normal operation, even with petrol engines, due to the catalytic converter.
"In contrast, the CO content of an unfiltered petrol engine, as is to be expected in an emergency power unit, for example, can be one or even up to ten percent," says Guido Kaiser, explaining the dangers. Regarding diesel engines, Axel Hahn adds: "In the exhaust coolers commonly used on board, soot components can 'burn off' incompletely and cause CO to be produced, and petrol catalytic converters often only work at full power after ten minutes."
Three years ago, a 36-year-old mother and her ten-year-old daughter died in the cabin of a Bayliner 285 while moored on Lake Windermere. Apparently, the improvised exhaust and silencer system of a portable 230-volt petrol generator had come loose.
There was a carbon monoxide detector on board, but it was not connected to the power supply. The gases spread through the gaps in the bulkheads. The owner woke up with symptoms of poisoning and raised the alarm, but was unable to resuscitate the mother and her daughter.
A motorboat owner in Cardiff was also poisoned by engine exhaust fumes on 12 November 2016. Shortly after midday, two club mates found him unconscious in his cabin. The canopy was closed except for a zip, and the dugout engine had been running for around 45 minutes at the time. The rescue workers also suffered mild CO poisoning.
T wo cases from North America and Germany, which only just ended on a mild note, illustrate that it is not only exhaust fumes from combustion engines that pose a considerable danger, but that our need for warmth in frosty conditions and the operation of a heating system also harbour risks:
On their 32-foot motor cruiser "Rojan", 80-year-olds Ron and Janie Ressel closed the zips on the cockpit deck in 2010 after the temperature dropped to 8 degrees Celsius during their December passage to Captiva Island off the west coast of Florida.
As her daughter later reported on the American portal boatus.com, Janie turned round at the helm to change the watch and saw her husband slumped in the cockpit. With the last of her strength, she was able to make an emergency call, but with the best will in the world, she was only able to disengage one of the two engines, so that the boat circled in the water, but soon received help thanks to the position information.
The couple was taken ashore in a U.S. Coast Guard inflatable boat and from there by ambulance and helicopter to a hospital. Although conscious for some time, Janie was apparently more severely poisoned and received hyperbaric oxygen therapy.
When it started to rain at the beginning of July 2015 during the passage on the Mittelland Canal towards Anderten, the 72-year-old owner closed the top of his "Snoopy", a Bayliner motorboat of the type Ciera 2655, and switched on the gas heating. He was joined below deck by his 44-year-old son and his three-year-old grandson.
All three fell unconscious shortly afterwards; the owner managed to disengage the engine before collapsing at the wheel. A passer-by saw the boat touching the sheet piling, apparently without a rudder, and courageously jumped on board at a favourable moment. Together with three other walkers, he was able to secure it on the bank and provide first aid until the rescue services arrived. Luckily for the crew, who suffered severe but not life-threatening carbon monoxide poisoning.
These events show: Although gas heaters generally have a comparatively low CO content in the exhaust air, they should be used with extreme caution on board. If the flame is weakened by wind or dirty nozzles, for example, or if the appliance is operated for a long period of time, poisoning is still possible.
For this reason, mobile gas heaters without an exhaust chimney, such as radiant heaters that are operated with 220 gram cartridges, have an oxygen sensor - but this is no guarantee against CO poisoning. Although the petroleum heaters offered by several suppliers, which are usually red in colour and the size and shape of a desk wastepaper basket, are available with an additional flame switch-off function if they fall over, carbon monoxide can still be produced.
In contrast, spirit cookers are quite harmless: "As almost pure alcohol is burnt, the carbon monoxide content in the exhaust air is extremely low. Safe operation is therefore guaranteed even in the cabin," says Jürgen Steindle from Dometic Waeco, explaining the advantage of this fuel in the well-known Origo burners.
"Nevertheless, the safety instructions must always be observed!" he advises. These include: do not use for heating, ventilate sufficiently and use under supervision.
So how can more security be created in view of the risks described? The easiest way is to get additional help. And this is quite inexpensive: battery-operated CO alarms are available from around 35 euros and should be placed at a medium height in the cabin.
For as little as 10 to 20 euros more, they offer more convenient displays or memory functions; both are useful, as they can be used to monitor a slight but still harmless increase in CO. In any case, devices for boats should comply with Euro standard EN 50291-2 from 2010.
Many work absolutely maintenance-free for five to ten years. The battery devices mentioned have been recommended by both the British Boat Safety Scheme and "Consumentengids", the Dutch partner magazine of the German magazine "Test".
The bottom line is that they are cheaper, more accurate and also faster than the old "measuring devices" used by miners: they liked to carry canaries with them against "bad weather", i.e. poisonous gases, as they show the typical symptoms of poisoning far sooner than humans.
"If the birds fell off the perch, that meant danger," says Guido Kaiser, describing the simple method. According to Axel Hahn, they already react to CO concentrations of well below 30 ppm - but only after a delay of a few minutes.
Today we are further ahead. However, current case numbers suggest that we need to raise awareness of an old and new danger: the popular barbecue. The barbecue belongs outside without any ifs and buts! The exhaust fumes from cooling charcoal are particularly insidious because the incomplete combustion produces a lot of CO.
Important facts and safety rules
Limits, causes and symptoms
Boats are naturally built as tightly as possible. Gases and vapours are therefore difficult to escape - including the dangerous carbon monoxide. Nobody is immune to this completely odourless and invisible gas. Warning signs: yellow or flickering instead of blue and steady flames in cookers, ovens and heaters. Unusual odour or smoke during combustion.
The internationally recognised US limit value is 83 ppm, which must not be exceeded for eight hours; otherwise there is already a risk of being unable to flee. The higher the concentration, the faster the effect: exposure to 6000 ppm (0.6 per cent) can lead to death in ten minutes, exposure to 30,000 ppm in just two minutes.
Behaviour in an emergency
Quick action is therefore necessary: Get people and animals out into the fresh air as quickly as possible. If possible, switch off the appliances causing the fire or turn off the gas supply, for example. In addition, always initiate rescue. Those affected can no longer save themselves or others and are often unable to call for help themselves.
Preventive measures
Only install appliances that are suitable for boats. Keep chimneys and connections in perfect order. Petrol appliances such as outboard motors (especially in the shaft) or generators produce a lot of CO. Be careful with exhaust fumes near the companionway. Heaters, barbecues and improvised installations do not belong in cabins or under canopies. Battery-operated CO warning devices complying with the EN 50291-2 standard are suitable as a precautionary measure, and are best installed at head height when seated, as the gas spreads almost evenly in rooms.
This text comes from BOOTE 9/2017.
