Identify one primary type of fire suppression system used onboard vessels.

The CO2 (carbon dioxide) fire suppression system is widely recognized as a primary fire suppression method used onboard vessels due to its effectiveness in handling certain types of fires, particularly those involving flammable liquids and gases. CO2 is a colorless, odorless gas that works by displacing oxygen in the atmosphere around the fire, effectively suffocating the flames and preventing combustion. This method is particularly advantageous in enclosed spaces like engine rooms and cargo holds, where it can be deployed without harming delicate machinery or electronics, as it does not leave behind residue or cause water damage.

Furthermore, for applications dealing with high-risk areas onboard vessels, the CO2 system is often equipped with alarms and safety measures to ensure crew members are protected during discharge, as it can pose a suffocation hazard in confined spaces. By quickly reducing the oxygen concentration to below the levels necessary for combustion, CO2 fire suppression systems provide an efficient and reliable means of fire control, which aligns with maritime safety regulations and practices.