The Marine Firefighting Institute

Newsletter # 8

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What Happened to the Air?

By Tom Guldner


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. 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. 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 to allow a circulation of fresh air, we will 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. Remember, not all oxygen deficient areas will be as well marked as the one pictured on the right.

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.) 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, tankers will 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.....


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."

Don't send your Firefighters into an environment that they are not trained to handle!

Stay safe,

Tom Guldner

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Previous Newsletters:

Newsletter # 1 "Marine Firefighting Training, Who needs it!"

Newsletter # 2 "Shipboard Basics"

Newsletter # 3 "Straight Stream Vs Fog Stream"

Newsletter #4 "Immigrants in Shipping Containers"

Newsletter #5 "Hazards of Refrigeration in the Shipping Industry"

Newsletter #6 "Stability at Shipboard Fires"

Newsletter #7 "2 in 2 out at Shipboard Fires"