Breathing compressed air underwater is a dangerous activity, as a scuba diver needs a continuous supply of air to sustain life.
In the majority of scuba dives, a diver will ascend to the surface with air in the tank. Fortunately, it is a rare occurrence when a scuba diver needs to access another source of air underwater.
Types of Scuba Diving Air Supplies
There are a range of alternate air supplies that a scuba diver can use when there is that sudden draw on the regulator and nothing flows:
- The dive buddy’s Octopus Second Stage. This is the most common; and few divers go scuba diving without the second stage regulator
- An emergency ascent bottle. This is a tiny scuba tank with a mouthpiece attached. It provides just enough air to get to the surface. The Spare Air is a popular brand.
- A separate complete scuba unit, incorporating a smaller tank. These are called a Pony Bottle.
- Buddy breathing. This is sharing the one second stage regulator with a scuba diver’s buddy. It requires a good understanding and specific techniques to do properly.
- Do an emergency ascent to get to the surface for air. This is the most dangerous situation and one that should always be avoided due to the possibility of an air embolism.
A scuba diver should be competent in the configuration and use of all the above systems.
A Scuba Diver Should be Prepared for Multiple Failures
A scuba diver should always be prepared for multiple failures of air sources. For example, the first stage on a regulator may fail making both the main and the Octopus second stage useless. Even though the scuba regulators are designed so that the common types of failure results in the regulator falling into downstream position, certain failures could result in no flow.
Another example is the tank valve suddenly blocking up. Maybe a bit of loose material that has broken away from the inside of the tank could get sucked into the valve.
Running Out of Air While Scuba Diving
Simply running out of air in the scuba tank again turns both second stage regulators into useless items of equipment. It doesn’t matter how many regulators are hanging off a tank if the scuba diver sucks the tank completely out of air while underwater at 60 feet.
And running out of air is not that uncommon, even with experienced divers. Some possibilities are:
- Being more active on a diver than usual due to high currents,
- Taking on a new underwater activity, such as photography,
- Having a new dive buddy, that moves faster underwater,
- Problems with bouyancy,
- A smaller tank than usual.
A Bad Air Fill Scuba Diving
A bad air fill may make a scuba tank and its various regulators dangerous. The most common way bad fill is carbon monoxide poisoning from an incorrectly set up filling station.
If the scuba diver is fortunate to realize the air fill is the problem, the only option for the scuba diver is to use a separate system, such as an Ascent Bottle or a Pony Bottle. However, as these items are not usually carried by most divers, the next available option is to buddy breathe.
Though in this example, both divers could be in trouble as it may be likely their tanks were both filled from the same filling station and probably both have bad air. A dangerous emergency ascent may be the only option in this scenario.
Having the air supply suddenly stop while scuba diving can be one of the most harrowing experiences underwater. Fortunately the sophisticated equipment available for today’s scuba diver means that this situation rarely occurs. However, when (or if) it does, there are many ways to deal with the situation.
Whatever type of secondary air system a scuba diver employs, it can always be argued if enough redundancy is ever enough.
Bruce Iliff - Hello from an Australian freelancer! I’ve been scratching articles together in Australia in a range of subjects for a number of ...
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