Lesson 1, Topic 1
In Progress



The regulator is the most important part of the scaffolding. Its function is to reduce the pressure of the air stored in the bottle and provide it to the diver at a breathable pressure, that is, at the same pressure as the water around it (ambient pressure).


The two-trachea regulator was created in 1945 by Jaques Yves Cousteau and Emile Gagnant. Based on the invention of Rouquayrol/Denayrouze (1864/1865), Cousteau and Gagnant designed and built a regulator of extreme simplicity, the CG45. This prototype gave rise to the single-story mistral regulator with two tracheas, which quickly became the most widespread in the world for its success.

It was this regulator that allowed the extraordinary development that diving has known since the 1950s, having since fallen into disuse, with the appearance of the regulator of a hose and two separate floors.


The new regulators are made up of two bodies joined by a hose, they are:

  • The First Floor
  • The Second Floor

The first floor of the regulator (high pressure floor) is metallic and has the function of reducing the high pressure to which the air is in the bottle to a fixed intermediate pressure (commonly called low pressure). This body is coupled to the bottle tap by the Yoke system or the DIN system, depending on the type of the tap outlet.

The first floor has several LP vents (air at intermediate pressure). From one of the LP outlets comes a hose that takes the air to the intermediate pressure to the second floor of the regulator.

The emergency second floor feeding hoses, the vest and the dry suit are connected to the remaining intermediate pressure outlets. The first floor also has one or two HP outlets (air directly to the pressure of the bottle), where the pressure gauge is connected.

The second floor, which can be metallic or high-strength plastic, reduces the intermediate pressure of the air to ambient pressure, thus allowing the diver to breathe effortlessly.

Basically, the second floor has an inlet valve, which regulates the intake of the air to inhale according to ambient pressure, a nozzle, through which the diver breathes, and an outlet valve, through which the expired air comes out. It also has a purge button that allows the diver to manually open the inlet valve and set the regulator to pour air continuously (continuous output) if necessary.


The use of an alternative source of air, which may be an emergency regulator or only a second emergency floor, is mandatory for all practitioners (NP EN 14153-1 2005).

The advantage of this alternative source is to allow the diver to use it to breathe in the event of a failure of the main regulator or, in an emergency situation, the diver can give air to a mate without having to share the main regulator.

Usually the second emergency floor is connected to one of the low pressure outputs of the first floor, through a much longer hose, to more easily reach the assisted diver. Some of these second floors have the nozzle facing the receiver, not being necessary to twist the hose to insert the nozzle into the mouth, which greatly facilitates the maneuver of giving air.

Alternatively, the diver can opt for a second emergency floor integrated into the vest filling system. The feeding of this second floor is done by the filling hose of the vest.

If the bottle tap has more than one outlet, the diver can mount a second regulator (instead of a second emergency floor). With this solution, even if a failure arises on the first floor of the main regulator, it is always possible to breathe through the regulator
emergency response.



After each use the regulator should be washed with fresh and dry water in the shade, preferably hanging from the first floor.

Whenever possible, the regulator should be washed still attached to the bottle and with the tap open.