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Marine Safety Alert: Inflatable boat safety: Do not over pressurize

March 17, 2023

The Coast Guard Office of Investigations and Analysis has released Marine Safety Alert 04-23 to highlight the importance of proper maintenance and adherence to manufacturer’s recommendations for filling/inflating buoyancy chambers on some models of inflatable boats.

During a recent investigation of an incident that occurred involving foreign cruise vessel operations in the Antarctic, a U.S. passenger was severely injured due to a Zodiac MILPRO model FC 580/MK5 keel bladder failure while underway on a sightseeing excursion. In calm weather, the keel bladder suddenly ruptured, sending the passenger several feet into the air
before landing onto the deck and sustaining serious injuries including a fractured femur. Another passenger was thrown overboard into the freezing water, risking hypothermia.

An investigation has identified that the keel bladder suffered a rupture due to excessive pressure in the tube. The recommended operating pressure by the manufacturer is 3.4 pounds per square inch (p.s.i) or 240 millibar pressure (mb). An on-scene survey of multiple inflatables on board the cruise ship noted pressures up to and exceeding 9 p.s.i. (620 mb) in other keel bladders. The keel bladder is not protected by a safety relief valve, and the manufacturer recommends that they be inflated with a foot pump to reduce the chance of over- pressurization. However, crewmembers were routinely using an air compressor to fill the buoyancy chambers (including the keel tube) prior to the incident. In addition, pressure levels were not being checked using a manometer as recommended by the manufacturer.

The Coast Guard strongly recommends that operators of cruise ships and other companies
employing inflatable boats:

  • Review all manufacturer recommendations for inflatable boat filling and maintenance to
    verify those procedures are being followed prior to any boat operations including
    passenger excursions.
  • Use manufacturer recommended inflation devices (e.g., a foot pump) and appropriate
    pressure measurement tools to avoid over-pressurization.
  • Verify that company policy addresses manufacturer recommendations and that crews are
    properly trained before operating and performing maintenance on inflatable boats.
  • Contact the manufacturer of your inflatable boats for any additional recommendations
    and/or training options they may offer.

This Safety Alert is provided for information purposes only and does not relieve any domestic or international safety, operational, or material requirement. Developed by Activities Europe and distributed by the Office of Investigations and Analysis. Please address questions to

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This blog is not a replacement or substitute for the formal posting of regulations and updates or existing processes for receiving formal feedback of the same. Links provided on this blog will direct the reader to official publications, such as the Federal Register, Homeport and the Code of Federal Regulations. These publications remain the official source for regulatory information published by the Coast Guard.