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Rotten egg smell aboard boat

  • Blog
  • May 19, 2023

The smell of rotten eggs is familiar to everyone. If this smell can suddenly be smelled on the boat, it is a sign of a life-threatening situation, and immediate action is essential!

What is it?

The smell of rotten eggs comes from H2S gas, also known as hydrogen sulfide. H2S is especially dangerous because it is highly toxic. In addition, it is also highly flammable. Moreover, it is heavier than air, so in enclosed spaces such as a boat, it will accumulate at the bottom of the vessel. Good to know; from 1ppm you can smell it, but above 100ppm the olfactory system becomes paralyzed and you will no longer smell the gas. Because it accumulates low to the ground, animals and children will be the first to be affected.

Poisoning by H2S

When you become poisoned by H2S you will experience symptoms such as headache, watery eyes, nausea, vomiting, sore throat, dizziness, confusion, shortness of breath, chest pain and heart palpitations. Eventually you will pass out, resulting in death. And unfortunately, it actually happens, as in the case of this couple (link).

What should you do if there is a rotten egg smell on board?

Do you smell the smell of rotten eggs on board? If so, act immediately!

  1. Let everyone disembark
  2. Turn off main switches on the way out
  3. On the way out, open as many windows and shutters as possible
  4. Take the vessel off shore power by unplugging the shore power cable outside
  5. If necessary, call 911
  6. Ventilate the vessel very thoroughly
  7. Get the cause found and resolved.

What causes H2S to be released?

H2S gas can be released due to a failure in the electrical system. When batteries are overcharged for long periods of time, the battery acid starts to boil. This then comes out of the battery as H2S gas. So it can be caused by overcharging the batteries or an internal defect in the battery.

How is it preventable?

To prevent the release of H2S, it is important that the electrical system is in order. Below are some tips to make sure it doesn't happen to you.

  • Have the electrical system checked regularly, but at least every 2 years
  • Replace batteries that have gone bad.
  • Do you need to replace 1 battery? Replace the batteries connected in parallel with it. This prevents the oldest battery from destroying the newer one.


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