Electro-Galvanic Fuel Cell (EGFC) – Oxygen Measurement in Scuba Diving


Electro-galvanic fuel cells (EGFCs) are electrical devices specifically designed to measure the concentration of oxygen in dive gear, such as scuba tanks and rebreather systems. This entry provides an overview of the operation and importance of EGFCs in scuba diving, discusses their history and development, and examines their role in ensuring diver safety and enhancing the overall diving experience.

History and Development

EGFC technology traces its roots back to the 1960s when it was first utilized for measuring oxygen levels in life support systems for manned space missions. As the technology advanced, it was adapted to meet the needs of the scuba diving community, providing a reliable and accurate method for monitoring oxygen levels in dive gear.

The original EGFCs were large and bulky, limiting their application in scuba diving. However, with advances in miniaturization and material science, modern EGFCs have become compact, lightweight, and more resilient to harsh underwater environments, making them an indispensable component of contemporary dive gear.

Operation and Principle

EGFCs operate on the principle of electrochemical oxidation, which is the process of oxidizing a substance by transferring electrons to an electrode. In the case of EGFCs, oxygen molecules from the dive gear are diffused across a selectively permeable membrane and react with an electrolyte solution, typically potassium hydroxide (KOH), creating an electrochemical reaction. This reaction generates an electrical current that is directly proportional to the concentration of oxygen in the dive gear.

The generated electrical current is then measured and converted into an oxygen partial pressure (ppO2) reading, which is displayed on the dive computer or other monitoring devices. The ppO2 reading is essential for divers to monitor their oxygen levels and make necessary adjustments to ensure a safe and enjoyable dive.

Importance in Scuba Diving

  1. Safety: Monitoring oxygen levels is crucial for diver safety. Inadequate oxygen levels can lead to hypoxia, which can cause unconsciousness and even death, while excessive oxygen levels can result in oxygen toxicity, causing convulsions, nausea, and dizziness. EGFCs provide accurate and real-time oxygen readings, allowing divers to manage their breathing gas mixtures and avoid these dangerous situations.
  2. Nitrox and Trimix Diving: Nitrox and trimix are alternative breathing gas mixtures containing higher percentages of oxygen and helium, respectively, compared to regular air. These mixtures enable divers to extend their bottom time, reduce decompression stops, and minimize the risk of decompression sickness. Using an EGFC to monitor oxygen levels is critical for managing these gas mixtures and ensuring safe dives.
  3. Rebreather Systems: Rebreathers are advanced scuba systems that recycle exhaled gas by removing carbon dioxide and replenishing the oxygen content. EGFCs play a vital role in rebreather systems by continuously monitoring oxygen levels, ensuring that the diver receives the correct mixture and maintaining the optimal breathing loop.
  4. Dive Planning and Execution: Accurate oxygen level measurements provided by EGFCs allow divers to plan their dives more effectively, considering depth limits, decompression requirements, and gas consumption. This information is crucial in preventing accidents and ensuring that divers stay within safe limits.

Maintenance and Reliability

EGFCs are generally low-maintenance devices; however, they do require periodic calibration and replacement of the electrolyte solution. Most modern EGFCs are designed to be user-serviceable, with manufacturers providing detailed instructions and support.

Despite their reliability, divers should never solely rely on EGFCs or any other single piece of equipment for their safety. It is essential to have backup systems and follow proper dive planning, gas management, and

safety protocols to minimize risks during a dive. Regular maintenance and inspection of all dive gear, including EGFCs, can help ensure their optimal performance and longevity.

Challenges and Future Developments

Although EGFCs have proven to be reliable and accurate in measuring oxygen levels in scuba diving applications, they are not without challenges. Some of the limitations of current EGFC technology include:

  1. Sensitivity to Contaminants: EGFCs can be sensitive to contaminants in the breathing gas, such as volatile organic compounds, which can interfere with the electrochemical reaction and cause false readings. Divers must be vigilant in using clean and properly filtered gas to minimize the risk of contamination.
  2. Limited Lifespan: The lifespan of an EGFC depends on various factors, including usage, maintenance, and storage conditions. Typically, an EGFC can last between one to three years. Regular replacement of the electrolyte solution and proper storage can extend the life of the device.
  3. Temperature Effects: The performance of EGFCs can be affected by extreme temperatures, as the electrochemical reaction rate may be impacted. Advanced EGFCs incorporate temperature compensation mechanisms to mitigate this issue, but divers should still be aware of the limitations in extreme temperature conditions.

Future developments in EGFC technology are expected to address some of these challenges. Researchers are exploring the use of alternative materials and electrochemical processes to improve the sensitivity, accuracy, and lifespan of these devices. Additionally, advancements in sensor technology, microelectronics, and data processing may lead to the development of more advanced and reliable EGFCs for scuba diving applications.


Electro-galvanic fuel cells are essential components of modern scuba diving gear, providing accurate and real-time measurements of oxygen concentrations in breathing gas mixtures. Their application in dive planning, gas management, and rebreather systems has contributed to improving diver safety and enhancing the overall scuba diving experience. As technology continues to evolve, it is expected that EGFCs will become even more reliable, accurate, and versatile, further solidifying their place as an indispensable tool for scuba divers.