Don't open the door after releasing CO2 within 24 or 48 hour although noticeably reduction in heat and smoke.

                    Premature reopening of fire area causes re-ignition
While underway a towing vessel with six crewmembers on board experienced an engine room fire. The chief engineer was in the engine room when the fire broke out. The only exit was an accommodation ladder which was in the path of the oil spray fire. The chief engineer exited through the fire, which ignited his clothing. The other crewmembers, who had also been alerted to the fire, discovered the chief engineer and extinguished the flames on his clothing. Nonetheless, the chief engineer suffered burns on more than 90 percent of his body.

As a first response, the crew released CO₂ from the vessel’s fire suppression system into the engine room and extinguished the fire. After observing a noticeable reduction in heat and smoke, the Master reported that the fire was extinguished and crewmembers opened the doors to the vessel’s superstructure and began de-smoking it. However, this action compromised the fire boundary by allowing CO₂ to escape and fresh air to enter the interior of the vessel, which caused the fire to reflash and rage out of control, consuming most of the tug’s superstructure. The crew had to abandon ship and were later rescued by SAR resources.

The vessel’s chief engineer was fatally injured, and the five remaining crewmembers suffered minor injuries.

Findings of the report* The engine room fire was probably caused by the ignition of lubricating oil that sprayed from a fatigue-fractured fitting on one of the main engine’s pre-lubrication oil pumps onto the hot surface of the main engine’s exhaust manifold.
* Contributing to the extent of the fire damage was the crewmembers’ compromise of the fire boundaries when they prematurely began de-smoking the vessel’s superstructure.
* The inability to completely secure the engine room’s fire boundaries also exacerbated the consequences of the fire.
* The abundance of flammable material throughout the vessel was also a contributing factor to the severity of the fire.

Editor’s Note: This is but one example of how the premature opening up of a fire scene can be disastrous. In my past activities as an accident investigator I have come across this same phenomenon on several occasions, especially for fires in the cargo hold. Essentially, once the fire area has been closed down and CO₂ released, there is usually no overriding reason to open up until absolutely certain that all sources of heat have been eliminated. This can take time; up to 24 or even 48 hours. Another tip – if at all possible, do not open up until additional help can be mustered such as SAR resources or port facilities.