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Published on 07/01/2022

Toxic gas onboard vessels – how you can avoid deadly consequences

Ships are a common ground for a range of toxic gas build up.

Gas on board is a common conundrum for crews and companies operating vessels at sea. Often, gas is an essential requirement for the day-to-day running of a ship – otherwise it is precious cargo.

Managing and mitigating the risks associated with gas. Gases represent a unique number of potential issues, many of which become even more challenging at sea. 


Gases pose a unique threat because they can cause injury or death in a variety of ways. The specific dangers associated with gas depend on its unique chemical composition, but some common risks to be aware of include:

*Asphyxiation: Gases can cause a person to stop breathing at certain quantities – a risk that becomes even more serious in the confined spaces we commonly find on board a sea-going vessel.

*Illness via inhalation: Certain gases can act as irritants when they come into contact with the skin, causing a variety of symptoms if they are inhaled in varying quantities depending on how toxic or poisonous the gas may be. Gases that have no smell or taste are particularly dangerous, as crew members may not realise until it is too late that they have been exposed.

*Drowsiness/unconsciousness: Some gases cause unconsciousness even when inhaled in small quantities. As mentioned above, it’s not always possible to detect a gas leak using the five senses alone – so this can happen very quickly without protective measures in place. Unconsciousness can pose a number of safety risks associated with the gas such as inability to escape the inhalation of toxic quantities, but also puts the person who is incapacitated in immediate physical danger.

*Fire: Many gases are flammable to varying degrees – posing a fire risk on board if they are allowed to leak and pool. Some gases are incredibly sensitive to the smallest spark or flame and can combust very easily. Where a gas has seeped out undetected a large-scale fire could break out rapidly – and could be difficult to control.

*Explosion: Like flammable gases, potentially explosive gases may not need much exposure or a significant leak to cause a deadly incident on board.


Although some vessels may carry gases routinely as cargo, there are a number that actively require gases on board for a number of essential functions. It’s likely that at least one or more of these gases will be on board a sea-going vessel at any given time.

Each gas behaves and presents itself in a unique way, with various key risks and management protocols to be aware of for each.

*Hydrogen Sulfide – Toxic, corrosive and highly flammable, H2S can cause headaches, skin and eye irritation, nausea and unconsciousness. H2S occurs naturally during the breakdown of organic matter such as sewage, waste water and foodstuffs. You can read our guide sharing key insights into the many dangers of Hydrogen here.

*Methane – High levels of methane (CH4) in the air reduces oxygen levels, leading to slurred speech, impaired vision, headache, nausea and vomiting and mood swings. When left undetected and untreated this can lead to raised heart rate, instability and unconsciousness.

*Acetylene: Commonly used in welding, acetylene (C2H2) can cause headaches, light-headedness, nausea and unconsciousness when inhaled. In its liquid form acetylene also causes frostbite.

*Oxygen: Oxygen (O2) is highly reactive – and behaves differently to other inert gases when compressed. Oxygen canisters pose a number of threats including fire and explosion. Inhaling pure oxygen can cause a number of symptoms including nausea, vision loss, unconsciousness and fitting.

*Liquid Propane (LPG) – Often used as fuel especially on smaller vessels, LPG can be extremely dangerous – heavier than air, it flows like water and can quickly accumulate in confined spaces posing risk of combustion and explosion.

*Carbon Monoxide (CO) – Often produced as a by-product of burning fuel and known as the ‘silent killer’, carbon monoxide is undetectable through the senses alone. Please see our full guide to understanding carbon monoxide here.


Managing gas on board and ensuring that it is safely stored and handled only represents one portion of control efforts needed to ensure complete safety and peace of mind. Even when you put stringent measures in place to avoid them, potentially dangerous incidents can still occur.

That’s where gas detectors provide a protective buffer, ensuring that should an unexpected leak occur, crew are alerted in a timely manner and can take appropriate action. There are two main types of gas detection hardware all sea-going vessels should have on board.

Portable gas detectors: Carried on your person, portable gas detectors offer individual protection for each crew member. The highly sensitive detector will sound an alarm if it identifies even minute levels of gas and can be calibrated to suit your needs.

Fixed gas detectors: Fixed gas detectors are installed at various points around a vessel, much like a carbon monoxide or fire alarm in the home. As fixed gas detectors are designed to raise the alarm in the immediate vicinity in the event of a gas leak, sufficient coverage is key.

Both types of gas detection device have their own advantages – but it’s not a case of either/or. Portable and fixed gas detectors are designed to work in tandem with one another, providing full protective coverage on board.


At Martek Marine we take the risks associated with gases incredibly seriously – and with over __ years’ experience in marine safety and risk management, we’re dedicated to developing durable, dependable solutions to a variety of risks posed at sea.

Our portable and fixed gas detection devices are consistently rated best on the market for their comprehensive function and reliability. Whatever method or model you choose, gas detection must be precise – so it’s crucial that the technology you trust is sensitive and dependably enough to get the job done when you need it most.

Our Marine 4 model offers unrivalled protection against the dangers of gas leaks – built to last featuring simple one-button operation and flexible configuration. Detecting four key gases simultaneously (methane, oxygen, carbon monoxide, hydrogen sulphide – alongside other flammable gases), Marine 4 has been specifically developed for use at sea, providing robust and reliable gas leak prevention.

Our three fixed gas detector models demonstrate the same reliability, ease of use and precision operation. The MM2000 features dual alarms and meets ExxonMobil Minimum Environmental and Safety Criteria Levels, bespoke-built by our specialist team of engineers. Fully SOLAS and ISGOTT compliant, the MM2000 can detect up to 32 potential threats at any time.

For tailored support from our team on fixed or portable gas detection solutions, get in touch today.