An escape set is an apparatus designed to allow survival in an environment that has too little oxygen or none at all. The primary use for escape sets is on submarines, though they can also be used in other situations that involve low oxygen environments. Early examples of escape sets consisted only of an air bag, which was typically not sufficient to keep a person alive long enough for a successful rescue. Later units made use of rebreather technology, which has also led to the use of escape sets in dry land applications, such as mines. A similar device, known as a smoke hood, can be used to prevent smoke inhalation during a fire.
The development of the escape set coincided with the early use of submarines in military applications. There was initially no way to recover a crew from downed or malfunctioning submarines, so a variety of methods were tried. A simple air bag was able to keep crew members alive for a while, though this often did not provide enough oxygen for the individual to reach the surface. Closed system bags can also lead to other issues, as they eventually become filled with air that has high amounts of carbon dioxide. When the rebreather was developed, it was combined with the older air bag concept to create something like the modern escape set.
A basic escape set design consists of a mask or head covering, bottled oxygen, and some type of rebreather apparatus. The purpose of a rebreather is to scrub carbon dioxide out of exhaled air using a variety of similar mechanisms, and then to introduce additional oxygen from an external source. This type of device can keep a limited amount of breathing gas usable for an extended period of time, increasing the likelihood of survival when escaping from a submarine, mine,or another dangerous environment. Rebreathers have also been used throughout the years by military divers, photographers, and other people that could benefit from the lack of constant bubbles associated with self-contained underwater breathing apparatus (SCUBA) diving.
Modern escape sets often include a variety of additional features that can increase the user's safety. The mask is often incorporated with a hood that can help keep the nose and mouth from being filled with water. An escape set may also be built into a thermally insulated immersion suit that provides similar protection to a diving drysuit. The primary limitation associated with escape sets is the breathing gas, which typically restricts them to relatively shallow use. Deep water rescue usually involves more complex devices, such as escape capsules or rescue submarines.