Vacuum packed ….
Whilst commissioning an incinerator, six people were trapped inside the incinerator room due to the strong vacuum (negative pressure) in the room.
The incident happened when the air supply damper was closed and the incinerator combustion air fan drew exhaust from the room, creating a vacuum inside. Smoke filled the room due to a burner seal failure. The door to the room was held shut due to differential pressure, trapping the personnel inside. This near miss could have resulted in a fatality.
Differential pressures can occur as a result of improper operation of machinery room dampers, mechanical ventilation, or an AC unit. If these ventilation systems and dampers are not operated correctly it could result in unsafe conditions like those described above. Other near misses reported include three medical related finger injuries due to differential pressures. Not understanding the dangers of differential pressures can also cause machinery and equipment damage, serious injury and fatality.
It is important to remember that good seamanship means to always:
- Ensure that ventilation & dampers are controlled as intended for normal operation and maintained properly;
- Ensure vents/dampers are open before starting mechanical ventilation;
- Look for signs of excessive differential pressure and investigate the reason; and
- Maintain a slight positive pressure inside the accommodation, especially during cargo handling.
- Close vent flaps / dampers against forced ventilation except in emergency;
- Deviate from normal ventilation practice without carefully assessing the risks.