Oxygen can kill! Do you see this as a strange statement?
We know without oxygen we cannot live. When we go up to higher altitudes, climbing hill, with less pressure we feel altitude sickness which is due to slight deficiency in oxygen. Need not mention how long we can hold our breath. No oxygen means death!
But more oxygen is also dangerous. In shipping there are two terms related to dangers of oxygen. They are
1. Oxygen depleted atmosphere
2. Oxygen enriched atmosphere
We will look at both scenarios, more oxygen and less oxygen, and find out dangers involved in shipping.
Oxygen Depleted Atmosphere
Earth’s atmosphere contains approximately 21% of oxygen if this percentage goes up or down then we are in a dangerous situation. First let us look at reduction of oxygen in shipping containers.
There are many cargoes which can cause depletion of oxygen, corroding scrap metals can deplete oxygen in a closed container or cargo hold. Oil Seeds, Copra, Fishmeal, Dry Ice, Charcoal etc. causes serious depletion in oxygen level.
Any atmosphere which has less than 19.5% oxygen is oxygen depleted atmosphere however one shall not enter any place where oxygen level is less than 20.8%!!
We have heard or read in news prints many cases involving workers dying in sewage or any enclosed spaces. In some cases co-workers go in to rescue those fallen without realizing the danger or low oxygen or presence of toxic or flammable atmosphere and fall victim themselves.
In shipping International Maritime Organization has issued Recommendations for Entering Enclosed Spaces Aboard Ships.
Effects of Oxygen levels
|22 %||Oxygen enriched atmosphere|
|19.5%||Oxygen deficient atmosphere|
|16%||Impaired judgement and breathing|
|14%||Rapid fatigue and faulty judgement|
|11%||Difficult breathing and death in a few minutes|
Oxygen Enriched atmosphere
Oxygen enrichment can be caused by various sources like, leaking oxygen cylinders, chemical reactions, inadvertent or accidental activation of oxygen generators carried as cargo etc. If the atmosphere is enriched with oxygen combustible materials can catch fire more easily and will burn more vigorously. Oxygen seriously reacts with grease. Even while operating the valves or regulators of oxygen cylinders never wear gloves contaminated with oil or grease or by hands contaminated with oil or grease, if there is a leak from cylinder you will end up having serious injuries.
A person who spent little time in an oxygen enriched atmosphere can cause serious burns if he/she light a cigarette !!
Oxygen enriched or depleted or containers having toxic or flammable atmosphere are too dangerous to enter and have resulted in fatalities in the past.
Section 220.127.116.11.2 of IMDG Code warns the possibility of an unsafe concentration of toxic or flammable vapours or an oxygen-enriched or -depleted atmosphere in containers.
There are many Dos and Donts about oxygen we must adopt the appropriate safety measures in our work place taking inputs from International and National regulations and recommendations.