Open Circuit Scuba: Breathing Apparatus and its Environmental Impact

Open circuit scuba is a breathing apparatus used by divers to facilitate underwater exploration and activities. This type of equipment allows divers to breathe underwater by providing them with a continuous supply of compressed air from a tank. Unlike closed-circuit rebreathers, which recycle the exhaled air after removing carbon dioxide and replenishing oxygen, open circuit scuba systems discharge exhaled air into the surrounding environment, with no part of it being re-breathed by the diver. This article delves into the various aspects of open circuit scuba, its components, advantages and disadvantages, and environmental considerations.

Components of an Open Circuit Scuba System

An open circuit scuba system comprises several essential components, including:

  1. Air tank: A high-pressure cylinder made from steel or aluminum, containing compressed air for breathing underwater. The tank’s capacity is typically measured in liters, with common sizes ranging from 3 to 18 liters.
  2. Regulator: A device that connects to the air tank and reduces the high-pressure air to a breathable pressure. The regulator consists of a first stage, which attaches to the tank valve, and a second stage, which delivers the air to the diver’s mouth.
  3. Submersible Pressure Gauge (SPG): A device that displays the remaining air pressure in the tank, enabling the diver to monitor air consumption and plan dives accordingly.
  4. Buoyancy Control Device (BCD): A vest-like apparatus that helps divers maintain neutral buoyancy underwater by inflating or deflating air bladders. BCDs also serve as a harness for attaching the air tank and other diving equipment.
  5. Low-pressure inflator hose: A hose connecting the regulator to the BCD, allowing the diver to inflate or deflate the BCD as needed.
  6. Mouthpiece: The part of the second stage regulator that the diver bites down on to receive air, creating a watertight seal in the process.

Advantages of Open Circuit Scuba

Open circuit scuba systems offer several benefits for divers, such as:

  1. Simplicity: These systems have a straightforward design with fewer components, making them easier to use, maintain, and troubleshoot.
  2. Affordability: Open circuit scuba equipment is generally more affordable compared to closed-circuit rebreathers, making it more accessible to recreational divers.
  3. Availability: Since open circuit scuba is more prevalent, air refills and equipment rentals are widely available at dive centers worldwide.
  4. Familiarity: The majority of scuba training courses focus on open circuit diving, making it the most familiar and comfortable option for most divers.

Disadvantages of Open Circuit Scuba

Despite its benefits, open circuit scuba also has some drawbacks, including:

  1. Limited dive time: Due to the consumption of air from the tank, dive time is limited by the tank’s capacity and the diver’s air consumption rate.
  2. Decreased stealth: The release of exhaled bubbles can disturb marine life and create noise, reducing the stealthiness of the diver.
  3. Increased decompression obligations: Open circuit scuba divers consume more gas at greater depths, leading to longer decompression stops and a higher risk of decompression sickness.

Environmental Considerations

The discharge of exhaled air into the environment by open circuit scuba systems has raised concerns about the potential impact on aquatic ecosystems. While the release of small amounts of exhaled air is generally considered harmless, large-scale diving operations in sensitive areas may contribute to the alteration of local water chemistry and negatively affect marine life.


Open circuit scuba is a popular and accessible means of underwater exploration, with its simplicity and affordability making it the go-to option for many recreational divers. Despite its limitations in terms of

dive time, stealth, and decompression obligations, its widespread use and familiarity make it the foundation of most scuba training courses. When diving with an open circuit scuba system, divers should be mindful of the potential environmental impact of their activities and adhere to best practices to minimize harm to aquatic ecosystems.

To further reduce the environmental footprint and address some of the limitations of open circuit scuba systems, divers may opt for alternative technologies such as closed-circuit rebreathers. These systems recycle exhaled air, removing carbon dioxide and adding oxygen as needed, resulting in longer dive times, increased stealth, and reduced decompression requirements. However, they come with increased complexity, cost, and maintenance requirements compared to open circuit scuba systems.

For those interested in pursuing open circuit scuba diving, it is essential to receive proper training and certification through a recognized organization such as PADI (Professional Association of Diving Instructors), NAUI (National Association of Underwater Instructors), or SSI (Scuba Schools International). These organizations offer various levels of certifications, starting with entry-level courses like Open Water Diver, followed by more advanced courses such as Advanced Open Water Diver, Rescue Diver, and Divemaster.

Proper equipment maintenance is crucial for the safe and efficient operation of open circuit scuba systems. Regular servicing of regulators, tanks, and buoyancy control devices by trained professionals can prevent equipment failure and extend the lifespan of these essential components. Additionally, divers should regularly inspect their gear for signs of wear and replace parts as needed.

In conclusion, open circuit scuba is a valuable tool for underwater exploration, offering both simplicity and affordability to divers worldwide. By understanding its advantages, disadvantages, and environmental implications, divers can make informed decisions about their equipment choices and diving practices to ensure safe, responsible, and enjoyable underwater experiences.