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Ventilation in vessels is the exchange of interior air for exterior. Additional handling of air includes heating, cooling, and dehumidifying under the umbrella designation HVAC.


Ventilation on vessels is important for a number of reasons -

  • Cooling of machinery spaces
  • Feed air for combustion
  • Evacuation of potentially deadly fumes, such as in confined spaces
  • Prevention of the concentration of airborne volatile chemicals
  • Maintain air quality in manned spaces, such as accommodation areas

Ventilation quantities are typically measured by either a mass flow (i.e. cubic feet per minute) or compartment exchanges per hour.

Types of Ventilation

Ventilation can be considered as two basic operations: intake and exhaust. Either may be forced, such as by fan, or natural.

  • Forced intake: A fan is used to draw fresh air into the compartment
  • Forced Exhaust: A fan is used to force compartment air to the exterior
  • Natural intake: A vent is used to direct air into the compartment
  • Natural exhaust: A vent is used to allow compartment air to escape

Ventilation Equipment

  • Louvres
  • Fans
  • Vents - mushroom, gooseneck


  • Spark arrestors
  • Ball/check valves
  • Fire dampers


  • Engine rooms typically used forced intake to provide cool feed air to combustion equipment, and natural exhaust through the funnel (utilizing the chimney effect).
  • Forced intake/natural exhaust can be used to control and clean incoming air, producing an overpressure situation in the fed compartments. This can be used in a 'citadel' arrangement to provide NBC protection.
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