The Rouquayrol - Denayrouze ‘Regulator’ and how the apparatus works:

In 1860 Benoit Rouquayrol patented a breathing apparatus which was in fact an early form of ‘demand-valve’ regulator similar in principle to the ones used for modern scuba diving today. Initially Rouquayrol devised his ‘regulator’ for use in smoke filled rooms and underground mines where smoke or poisonous gases made it impossible to breathe. However in 1864, after collaboration with a French navy lieutenant, ‘Auguste Denayrouze’, the apparatus was adapted for use underwater. The ‘demand valve’ principle is still used in all modern scuba diving regulators today.

When using the regulator underwater, the diver wears a nose-clip to prevent water entering his nose and to help with ‘clearing his ears’. He wears lead sole shoes to help him walk on the seabed and lead weights under his arms and on the regulator back-pack to prevent him floating upwards. The lack of vision was still a problem, so in 1866 Rouquayrol and Denayrouze decided to create a type of lens the diver could see through. A copper mask was built with a single window at the front and a strong brass ring at the rear clamped the mask to the diving suit.

The engraving above shows the diver wearing his suit; the weight at the back of the regulator and the weights under his arms are clearly visible. The mask also has two weights attached to it. Due to its shape the mask became known as the ’Groin’ which translates as ‘Pig-Snout’ from French.

The above photographs depict the oldest genuine Rouquayrol-Denayrouze regulator back-pack that is known to exist. It is the property of the Danish Navy’s Diving School in Kopenhagen, Denmark. The apparatus is not complete as the rubber diaphragm and the cover for the diaphragm are both missing. This early regulator is made of steel and is coated with black tar to help prevent it rusting in seawater. The Danish Navy also possesses the original Rouquayrol-Denayrouze air-pump and the ‘pig-snout’ mask. Photographs, David L.Dekker

The Danish Navy’s genuine Rouquayrol-Denayrouze ‘pig-snout’ mask is not the only design of its type. Instead of only one front window, a more recent design of ‘pig-snout’ mask has two extra small, round windows positioned on top and slightly on each side. This would give better all round vision from inside the mask. Photographs, David L.Dekker

Above: the Rouquayrol - Denayrouze regulator equipment with the ‘snout’ mask.

The Baltic Sea ‘amber’ divers were content with this ‘inconvenient masks’ but the French navy found the inconvenience to be a serious problem. About one year after the introduction of the ‘pig-snout’ mask (in 1867) the navy asked Rouquayrol and Denayrouze to solve the problem. This resulted in the design of the ‘3-bolt helmet’ which is shown in the above engraving. The ‘pig-snout’ mask developed a ‘back’ to transform it into a bonnet, and a breastplate carried the bonnet on the shoulders of the diver to form the complete helmet. The water-tight connection to the suit was accomplished with a 3-bolt flange which was built onto the bonnet and breastplate. The suit was then simply clamped between the flanges of the bonnet and breastplate. The engraving shows the very first design of the Denayrouze 3-bolt helmet of 1867. Since then, the 3-bolt helmet design became a new world standard adopted by the navies of France, Germany, Austria, Russia, Netherlands and countless smaller enterprises. Three-bolt helmets are still manufactured in China and Russia today.

In 2002 I was lucky to find a genuine Denayrouze 3-bolt helmet in an antiques shop in the south of France. The helmet was made to be used with either a ‘regulator’ or as a ‘ventilated’ (free flow) helmet. The idea of having a working regulator was exciting and I started to ask around for information. A friend from the Danish ‘Historical Diving Society’ ( ) knew that such an apparatus existed and was in the possession of the Danish Navy. We contacted the relevant authorities and together with a friend of mine, (Rob Krul, who owns a machine-shop / factory here in Holland) we drove to Kopenhagen. We were permitted to examine the apparatus and take the necessary measurements from the original regulator. Using this information we were able to re-build a small series of reproduction regulators. These replicas were fully functional and we occasionally dive with them. (4 new chapters dedicated to this project along with various other projects can be visited HERE. There are also articles published in ‘The Journal of Diving History’, ‘Classic Diver’ and ‘Historical Diving Times’ which explain our projects in greater detail). With the replica regulator I was able to complete my 3-bolt Denayrouze helmet and later on we also built a limited series of the ‘pig-snout’ masks. To keep the historical chronology correct, the first picture below depicts the early style of apparatus with the ‘pig-snout’ mask.

The mask and regulator shown here are replicas, but the rest of the apparatus uses genuine parts. The air-pump is of interest as it is the only surviving model known to exist today. It is the first pattern of a Rouquayrol-Denayrouze air-pump which Rouquayrol secured a ‘patent’ for in 1863. This pump is illustrated in the ‘Manuel du Matelot-Plongeur’ from 1866: a ‘Seaman-Divers manual’ written by Auguste Denayrouze.

The engraving shows a diver with a ‘pig-snout’ mask next to the air-pump from 1863. The recent photographs in the composition show the pump I discovered in 2002. This model of air-pump was manufactured for only a limited time period and was soon replaced by the air-pump which became known as the ‘pompe hydraulique’. The ‘pompe hydraulique’ is shown in the photograph along with the Denayrouze apparatus which I restored with parts, having found the helmet in France in 2002.

Rebuilding the Rouquayrol Denayrouze ‘Pig-Snout’ diving apparatus

The Rouquayrol - Denayrouze Regulator were made of steel

The first regulators were made from steel and coated with black tar to help prevent them rusting.

Rouquayrol - Denayrouze ‘regulator’ apparatus in use by German ‘amber divers’

The ‘pig-snout’ mask was only manufactured for a very short time in France but was used for many decades by German ‘amber’ divers. The problem that the mask fell forwards due to a lack of support by a breastplate was an advantage for the amber diver who was constantly looking in a downward direction at the seabed. Engravings, David L.Dekker collection

1866 / 1867. Transition from the ‘Pig - Snout’ mask to 3 bolt helmet

Rouquayrol air-pump ‘Model 1863’

The illustrations above show a regulator that is identical to the design of Rouquayrol-Denayrouze. It is a more recent version which is made of brass, bronze and copper by the German company ‘Ludwig von Bremen’ of Kiel. Original Rouquayrol-Denayrouze regulators were made of steel. The regulator (figs. 4 and 5) is worn on the divers’ back. Air is pumped from the surface to tank ‘A’ and the air-hose is connected to ‘c’. On top of tank ‘A’ is an air-chamber (fig. 5B) which is closed on top with a rubber diaphragm (fig. 7). (Fig. 5G): this diaphragm is held in place with a brass ring with a clamp (fig. 8). (Fig. 5 z): between the tank ‘A’ and the air-chamber (fig. 5B) there is a valve (fig. 1) which is connected to the rubber diaphragm (fig 5G) with nuts and rings ‘D’ (fig. 5). From the side of the air-chamber is tube ‘f’ (fig. 4) and on this is a short hose that is connected to a mouthpiece at the other end. When the diver inhales through this mouthpiece the rubber diaphragm (fig. 5G) on top of the air-chamber (fig. 5B) is drawn down and opens the valve (fig. 1) between the tank ‘A’ and the air-chamber (fig. 5B), thus allowing the air supply to flow to the diver. On tube ‘f’ (fig. 4) between the mouthpiece and the air-chamber is installed a ‘bec de canard’ (‘flap’ or ‘duck- valve’, fig. 4h) to allow the exhaled air to escape.

The Rouquayrol - Denayrouze ‘Regulator’ in use under water

1860 Benoit Rouquayrol - Auguste Denayrouze

Over the following years I managed to slowly acquire the various parts to complete the set of apparatus. However the apparatus shown here has a ‘replica’ regulator back-pack. The hose shown on top of the helmet at to the right of the diver is the speaking tube: in 1874 Auguste Denayrouze’s brother Louis Denayrouze, patented this system which is simply a tube (identical to an air-hose) with a membrane on either side. The membrane inside the helmet covers a large part of the back and top of the helmet, so when the diver speaks to the surface assistant his voice can be heard through the membrane at the tender’s end of the speaking tube. The diver can also hear the tender when he speaks from his end. To date, I have not been able to find the exact date when the second model ‘Pompe Hydraulique’ air-pump was introduced, but it was probably around 1870. The difference between the ‘first model’ air-pump and the ‘second model’ is the shape of the cylinders: the early pump has cylinders with a ‘bell shape’ top, while the second model has flat top cylinders. The pump used with the ‘pig-snout’ mask apparatus by the Danish Navy is of the second model and it has the company name ‘Rouquayrol-Denayrouze’ cast into the iron base plate. Most pumps of this second model only have the name ‘Denayrouze’ casted into the base plate. Photographs, David L.Dekker

In the photographs below, the ‘regulator’ back-pack has been replaced by a normal lead weight and the air-hose has been connected directly to the helmet for diving use as a ‘ventilated’ (free flow) system.

Another interesting detail is the fact that where the equipment with the regulator only has a gauge at the junction where the two hoses from the pump are connected to the air-hose going to the regulator, the ventilated equipment shown here above has a tank at the surface between the pump and air-hose, this tank is in diameter identical to the tank of the regulator and was called the ‘reservoir intermediair’. Due to the lack of the tank incorporated in the regulator back pack an identical tank was placed on a tripod and the gauge has been fitted to it. This separate tank was important for several reasons: it allowed the water to condense (be trapped and held) inside the separate tank, so the condensate water could not pass down the diver’s air-hose and into his helmet. The ‘reservoir intermediair’ also allowed for a more even, regulated air supply to be fed to the diver. Later models incorporated an air-filter built inside the tank which provided a cleaner air supply to the diver. When using the regulator the gauge shows the pressure provided to the regulator which has to be held at a more or less constant pressure of one atmosphere above the ambient pressure for the regulator to work properly. With the ‘ventilated’ system the gauge would also indicate the depth the diver was at. Photographs, David L.Dekker

Denayrouze 3-bolt diving apparatus with regulator and ‘Pompe Hydraulique’

The Denayrouze ‘ventilated’ equipment ( ‘as above but without the regulator’ )

In 1873 Denayrouze introduced a ‘ventilated’ 3-bolt diving apparatus. The main difference with the regulator unit is that with a ‘ventilated’ system, the air is pumped into the helmet on one side and escaped through an exhaust-valve on the other side, thus allowing the diver to breathe freely inside the helmet (see photographs below).

In 2002 I was lucky to find an original Denayrouze 3-bolt helmet in a antiques shop in the south of France. The helmet was made to be used either with a ‘regulator’ or as a ‘ventilated’ (free-flow) helmet (see photographs below):

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