Skip to content

LTI: Carbon Monoxide (CO) poisoning during Oxy-Acetylene brazing

What happened

A crew member suffered from Carbon Monoxide (CO) poisoning during oxy-acetylene brazing. The incident occurred when the crew member was involved in the repair of a broken valve, part of the Freon pipe system for refrigeration. While doing the brazing on the gas return isolation valve, the crew member felt unwell, but continued the job. The task was completed after one hour and then the crew member felt breathing difficulties, was coughing and experienced chest pains. After a coffee break, the crew member sought medical assistance on board. Medical assessment showed had low oxygen saturation level. A medevac was activated due to possible respiratory distress or even heart problems.

What went right

  • The method statement for repair was to use oxy-acetylene brazing and TIG (Tungsten Inert Gas) welding methods;
  • All safety controls such as Hot Work PTW, Risk Assessment, Toolbox Talk were in place for the job.

What went wrong

  • The crew member did not wear a face mask during the welding job. The company’s procedures did not require the wearing of a face mask for this gas welding, although the wearing of a face mask was identified as a control measure in the risk assessment;
  • The risk assessment for the job was incomplete:
    • Wearing of a face mask was indicated in the PTW as an “additional protection only”;
    • The need for a portable exhaust ventilation system was not identified for this working area;
    • The risks and hazards associated with TIG welding were not identified;
  • The crew member did not take regular breaks during the task as indicated in the Risk Assessment, and kept on working when he felt ill rather than stopping and reconsidering;
  • The crew member was unaware of the risks and hazards associated with TIG welding. The molten metal gives off molecules of metal and ozone which are harmful to respiration.

Lessons learned

  • Review condition and availability of portable exhaust ventilation equipment onboard and order more if required;
  • Wear a welding mask when carrying out welding jobs;
  • Review Risk Assessment for the task with regard to:
    • Use of portable exhaust ventilation systems to ensure adequate ventilation;
    • Duration of exposure time and rest periods.
    • Regular testing of air in areas where CO may be present;
    • Risks and hazards associated with Tungsten Inert Gas (TIG) welding.
  • Use respirators with appropriate canisters, in conjunction with personal CO monitoring, for short periods under certain circumstances where CO levels are not exceedingly high (OSHA PEL for CO is 50ppm of air averaged during an 8-hour time period);
  • Further appropriate refresher training for welders on risk and hazards of all types of welding used onboard;
  • Further education for all crew about the sources and conditions that may result in CO poisoning as well as the symptoms and control of CO exposure.

Members may wish to refer to:

Safety Event

Published: 16 February 2023
Download: IMCA SF 05/23

Relevant life-saving rules:
IMCA Safety Flashes
Submit a Report

IMCA Safety Flashes summarise key safety matters and incidents, allowing lessons to be more easily learnt for the benefit of all. The effectiveness of the IMCA Safety Flash system depends on Members sharing information and so avoiding repeat incidents. Please consider adding [email protected] to your internal distribution list for safety alerts or manually submitting information on incidents you consider may be relevant. All information is anonymised or sanitised, as appropriate.

IMCA’s store terms and conditions ( apply to all downloads from IMCA’s website, including this document.

IMCA makes every effort to ensure the accuracy and reliability of the data contained in the documents it publishes, but IMCA shall not be liable for any guidance and/or recommendation and/or statement herein contained. The information contained in this document does not fulfil or replace any individual’s or Member's legal, regulatory or other duties or obligations in respect of their operations. Individuals and Members remain solely responsible for the safe, lawful and proper conduct of their operations.