The dangers associated with unventilated enclosed spaces on board ships are well known. The depletion of oxygen in the atmosphere may occur for a number of reasons. One example is rusting of steel constructions within such spaces, which may consume oxygen. Other examples are commodities which absorb oxygen and cargoes emitting gases which displace the oxygen or are themselves poisonous.
The average stevedore or crew member probably would not view a cargo of wood to represent any serious risk to human lives. However, even an innocent commodity may be able to kill if assisted by other circumstances.
In a recent case a vessel entered with the Association loaded a full cargo of sawn soft wood for two different discharge ports. The timber was unseasoned. This meant that a moisture content of up to 30 per cent would not be unusual at the time of loading. Furthermore, during processing the timber had been treated with the chemical pentachlorophenol (PCP), a chlorinated hydrocarbon insecticide and fungicide.
The climatic conditions during the voyage, including adverse weather with rain storms, caused the Master to decide that ventilation of the cargo holds should be restricted. One month after completion of loading the vessel arrived at the first port where approximately one third of the timber was discharged. Cargo was discharged from the upper part of all five cargo compartments without incident.
The vessel arrived at the next discharge port a week later. According to the practice at the port, entry formalities were initiated by the pilot and free pratique was granted as the vessel proceeded inward. After having completed the mooring operation the crew lowered the gangway before proceeding to open up the hatch covers. At the same time several stevedore gangs boarded the ship and immediately proceeded to the cargo hold.
A few minutes later one of the deck officers heard a commotion coming from forward. The stevedores advised that a number of their men had been evacuated from the cargo holds after experiencing breathing difficulties. One man had not come out of hold number one. The crew immediately brought sets of self-contained breathing apparatus to the scene and the emergency squad was mustered. The Chief Officer descended the hold wearing breathing apparatus. He ascertained that one stevedore was lying at the bottom of a ladder about 14 metres below the access way opening. Unfortunately, because of the bulky breathing apparatus he was wearing, the Chief Officer could not reach the bottom, since the way was partly obstructed by intruding cargo. Meanwhile, the port authority emergency services had been alerted. A fireman wearing a smaller breathing pack finally succeeded in reaching the stevedore who was then taken out of the hold. Tragically he could not be resuscitated. Two other stevedores affected during the incident were given quayside first aid and were discharged from the hospital after a short stay.
Immediately after the accident the atmosphere in all the holds was tested by an inspector appointed by the port authorities. One of the holds which had not been opened since the previous discharge port showed the greatest depletion in oxygen with a level as low as 2.8 per cent at the top of the hold, and 1.2 per cent at the bottom. The values for the other hold which had been opened varied from 10.3 per cent to 19.7 per cent when measured in the middle of the hold.
It is known that sawn unseasoned soft wood continues to absorb a certain amount of oxygen for a limited period after processing. However, the extreme depletion of oxygen levels to the very low values found in the holds of the ship is difficult to explain. Furthermore, there is no clear evidence that the possible presence of penthachlorophenol vapour in the holds may have been a factor.
The accident occurred in a rather difficult jurisdiction, and as a result the vessel was detained for more than a week pending the outcome of criminal investigations initiated by the local authorities. The CO fire extinguishing system for the cargo hold and the engine room was inspected and found in order. The investigations ultimately concluded that the accident was an act of God, and that there was no fault or negligence on the vessel.
The above tragic events illustrate the importance of safety procedures for entering unventilated enclosed spaces. Basically, it is required that after opening the enclosed space must be well ventilated and the atmosphere must be tested before personnel are given permission to enter. In the above case it was unfortunate that the keeness on the part of the stevedores to start work as soon as the vessel had berthed and to enter the holds even before the crew had finished opening all hatch covers resulted in the death of one of their number.