Aboard ship there are many areas that have hidden dangers of which the land-based firefighter may be unaware. I think that we all would be suspicious about entering a newly emptied cargo tank aboard an eight hundred foot gasoline tanker. We all know the problems with flammable gasses given of by flammable and combustible liquids.
However, would you also be concerned about entering the chain locker in the bow of this same vessel where only the anchor chain is stored? After all, what kind of a danger could all that nonflammable chain present?
What happens to the outside of the metal chain as it sits in the damp chain locker? The metal will start rusting. We all remember from our “Handbook of Fire Protection” that rusting is a form of oxidation. And oxidation consumes oxygen. The oxygen acts with the wet iron or steel and a pyrolysis reaction takes place. This “slow burning” gives off some heat but most of that is dissipated by the metals mass and the surrounding atmosphere. Later we will discuss cargos aboard which will not allow that heat to be dissipated so readily.
Our problem arises in the fact that this oxidation is using up the available oxygen that we need to survive. If the compartment in question has no inlet or outlet to allow a circulation of fresh air, we may have an oxygen deficient atmosphere.
Normal air contains twenty one percent (21%) oxygen. As this level is decreased, the danger to anyone entering that space increases. It becomes a hazard when the level drops below 19.5%.
The progression is as follows:
19.5% Minimum acceptable oxygen level.
15-19% Respiration increases. Poor judgment.
12-14% Decreased ability to work strenuously. Impair coordination.
10-12% Respiration increases. Lips blue
8-10% Mental failure. Fainting. Nausea Unconsciousness. Vomiting.
6-8% 8 minutes – fatal, 6 minutes – 50% fatal, 4-5 minutes – possible recovery.
4-6% Coma in 40 seconds. Death
A response to a ship fire or emergency should mandate the inclusion of oxygen meters as well as gas meters in your tool list. Any area aboard ship that is not normally occupied or entered should be considered suspicious.
Most vessels are made of steel. All of these metal surfaces are subject to the oxidation of rusting that we previously discussed. Just ask the ships deck hands who are constantly kept busy chipping the paint at the rusted areas. (US Navy photo above)
Air samples must be taken at all levels of the compartment prior to entry. If you do not have the proper sampling equipment ask a ships officer if they have these meters.
Generally all ships, but especially tankers, will have these meters on board. When at sea, older tankers clean their tanks and then members of the crew will enter for mucking out (that’s as messy as it sounds) and general maintenance. Before they are allowed to enter, the atmosphere is suppose to be checked. Regardless of whether these meters are available or not, ONLY QUALIFIED, CONFINED SPACE CERTIFIED personnel should ever enter any space considered a confined space. If you are in doubt as to whether an area is a confined space then “IT IS A CONFINED SPACE!”
Examples of Confined Spaces:
- Tanks
- Manholes
- Boilers
- Furnaces
- Sewers
- Silos
- Hoppers
- Vaults
- Pipes
- Trenches
- Tunnels
- Ducts
- Bins
- Pits
Potential Hazards in shipboard Confined Spaces
Oxygen Deficiency
<19.5% or >23.5% oxygen concentration
Combustibles
- Methane
- Hydrogen
- Acetylene
- Propane
- Gasoline fumes
- Toxic Materials
- Carbon Monoxide
- Hydrogen Sulfide
- Welding fumes
- Corrosives
Electricity
Mechanical Hazards
- Machinery
- Conveyers
There may be another naturally occurring area where you may encounter a low oxygen level. Some cargo will also eat up the oxygen within the cargo hold. Most organic cargos will undergo a ripening or a decomposition process while being transported. This can actually be considered a form of combustion and enough heat may be produced to cause ignition. We are more familiar with this when it is called spontaneous combustion.
A good example of this is wood pulp. This product is often carried on large barges and aboard Dry Bulk Carriers. The wood pulp will start to degrade in the presence of oxygen. in the process oxygen is consumed and if adequate ventilation is not provided the oxygen level may be reduced to dangerous levels. As mentioned, in this oxidation process heat will be produced and if confined with inadequate ventilation it may spontaneously ignite causing a deep-seated fire which may be extremely difficult to uncover for extinguishment.
In many cases the entire cargo must be unloaded in order to access the burning material. If the vessel is underway it may have to proceed to an unloading facility for extinguishment.
Many cargos may react in this same manner. Coal (see photo below) can be one of the most troublesome fires to extinguish. Wet coal will heat causing pockets of smoldering coal which is
one of the cargos which may have to be unloaded for final extinguishment.
Produce will ripen during shipment causing the same heat and oxygen consumption. The owners of the fruits and vegetables are not very happy about this and in my next article we will discuss some of the ways they are able slow the ripening process which will also dramatically effect the air problems your Firefighters will encounter.
To sum up, you should not trust any areas aboard ship where crew members do not regularly work. Even if there are no hazardous chemicals in use, the oxygen levels may be reduced to dangerous levels. When in doubt, test the atmosphere. If the fire situation requires it then full PPE and positive pressure masks should be worn (with the facepiece ON!)
Any area aboard which meets the criteria for a Confined Space should not be entered by anyone but Confined Space trained personnel. And if you are in doubt as to if the area is a confined then IT IS A CONFINED SPACE!
My seminars discuss all of the dangers which can be encountered aboard a ship. Gas inerting, Oxygen Deficient Atmospheres (in addition to the one discussed here), explosive atmospheres, entrapment dangers, electrical dangers (440 – 880v), and the list goes on. Placing your structurally trained firefighters into the marine environment without proper indoctrination and training is not only unsafe, it can also be legally devastating to your department or municipality.
The following is a quote from the National Fire Protection Associations Handbook of Fire Protection Chapter 15-1.2 of NFPA standard # 1405 dealing with volunteer, career, as well as mutual aid fire departments who have been defendants in law suits involving losses at ship fires, states:
“An understanding of the dangers inherent in marine fire fighting should include an understanding of the consequences of the failure to provide a standard of training, planning, response, and action
equivalent to that which a department provides on the land-based portions of its response area.”
This just in…
While I was writing this article, dealing with lack of air in many areas aboard ship, mariners were tragically killed in actual incidents which was warned about here. The following is from the Trade Winds web-site.
UK authorities are investigating the death last month of two seafarers on a Carisbrooke Shipping general cargo vessel. The 13,400-dwt Sally Ann C (built 2007)
The chief officer and the chief engineer collapsed in a cargo hold of the 13,400-dwt Sally Ann C (built 2007) on 13 March.
The ship’s second officer is said to have tried to help his two colleagues, but lost consciousness and had to be revived.
The Isle of Man-flagged vessel was off the coast of Senegal bound for Dakar carrying a cargo of timber when the incident occurred.
Additionally, three men died on the Suntis by entering one of its holds that was identified as “dangerous” and not to be entered without a permit and the hold being ventilated first.
At the bottom of the ladder leading into the hold, oxygen levels as low as 5% were found. “Such low levels cannot support life,” the MAIB said.
The full story can be found online at; http://www.tradewindsnews.com/casualties/357420/cargo-hold-claims-two
Don’t send your Firefighters into an environment that they are not trained to handle! Until next time, stay safe.
For more information, go to www.marinefirefighting.com
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