The work of breathing or WOB is in simple terms, the effort required by the lungs to breathe. But to be more accurate it refers to the energy expended to inhale and exhale a breathing gas. The WOB is usually expressed as work per unit volume.
Divers Alert Network or DAN is a non-profit agency that collects and analyze information for divers safety. It has branches that sell different diving oriented services and products such as insurance or oxygen providing kits or First Aid and CPR courses.
The SI or surface interval is the amount of time between 2 dives which is used to calculate the limits in consecutive dives.
The gauge pressure is the pressure shown by a gauge which was calibrated and zeroed using ambient surface pressure at sea level as a reference.
fsw or feet of seawater is a measurement unit of the imperial system and represent the pressure in 1 foot of seawater or about 15 psi. 33 feet is also roughly 1 atmosphere.
Its was in 1971 in Canada that the DCIEM or Defence and Civil Institute of Environmental Medicine was founded in a joint participation of military and civilian personnel. This lead to the development of dive tables that were more conservative than the US Navy tables.
Open circuit is the breathing system most commonly used for scuba diving. It is called open circuit because all the gas exhaled by the diver is expelled in the environment. A basic OC breathing apparatus is composed of a cylinder, a regulator first and second stage and a pressure gauge. The other systems are called CCR for closed circuit rebreather or SCR for semi-closed rebreather because they reuse in a loop all or part of the diver exhaled gas.
MSW or Metre Sea Water is the unit used in metric to measure the pressure divers are exposed to. For every meter of sea water the pressure is theoretically 0.1bar and is equal to 3.26336 fsw.
A DSMB or Delayed Surface Marker Buoy works the same as a SMB but it is inflated and deployed from underwater. It is composed of a surface marker buoy secured by a line on a spool or by a WDS. DSMB allow a diver to be located and spotted from the surface while still being at desired depth. It helps in preventing and avoiding accidents with boats and is considered mandatory in many places.
EAN or Enriched Air Nitrox is a mixture of gases for which content is the same as air but at different ratios. It has higher concentration of oxygen than the 20.8% found in regular air. EAN is used to reduce nitrogen exposition and saturation into the body. It gives longer bottom times at given depths than regular air.