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Before the Second World War, companies that produced the ARO oxygen rebreather were already present in Italy.

Through an initiative of the Italian Navy, the production of this equipment went to a single group called SIAS, which later changed its name to SALVAS, based in Rome and, some time later, moved its offices to Castelnuovo di Scrivia, where it is still located.

Immediately after the war, ARO continued to be the protagonist of the Italian diving tradition.

PIRELLI, a famous industry with a tradition in tires, manufactured diving equipment for the Italian Navy during World War II. Among them, the rebreathers ARO, whose models were POSEIDON and POLIFEMO.

The Italian surgeon, Alberto Novelli, who was reigning in the titles with Ennio Falco, was a free diving champion between 1951 and 1956.

Novelli, along with technician Peter Buggiani, patented the first two-stage regulator that was marketed by PIRELLI in 1959. Novelli was a consultant to the Center for Underwater Exploration of Italy.



Through his research, Alberto Novelli, has came to the conclusion that the air in the upper respiratory tract of the diver had not been used in the respiratory process, while the air of the diver's lungs contained the lowest oxygen levels and the highest levels of carbon dioxide.

Your project took this information into account for the manufacture of the first two-stage regulator. Named EXPLORER, Buggiani-Novelli patent, was produced in three models: MAIOR, STANDARD and MINOR. It was the first two-stage regulator produced in the world.



During expiration, the unused diver's air expanded the shells of the new Explorer regulator, closing the demand valve and activating the operation of a stainless steel cable. This cable allowed opening of the exhaust valve in the mouthpiece, which allowed the remaining exhaled air (already used by the diver) to escape into the aquatic environment.

After the inhalation, the air that was in the upper part of the airways and had been stored in the bi-valves shells, was re-breathed. With this, the closing of the chamber activated the demand valve for a new fresh air charge from the cylinder.



Cleaning of the hose/regulator assembly was similar in operation to other double hose regulators without non-return valves. If the diver lost his mouthpiece underwater, it should go up a bit and with the free flow generated, like that in any other double hose regulator of that time, would have the water removed from the hose.

However, none no-return valve could be used in this regulator model since the single hose worked for both: inhalation and exhalation.



If a serious problem occurred, such as flooding the hose and regulator camera, it was enough for the diver to manually compress the shells, which activated the inhalation valve and drained the hose through the mouthpiece and exhaust valve.

In August 29, 1959, along with Falco and Cesari Olgiaji, Novelli broked up the world record, using a Explorer regulator, reaching the depth of 131.35 meters, in a dive that lasted one hour and twenty minutes. 



The first stage of the regulator was coupled through the yoke to a cylinder in the inverted position. The bi-valve shell lung, the second stage of the regulator, was clipped at the height of the diver's left shoulder and received air through a medium pressure hose. The shells were chrome-plated brass and had the oval shape in Explorers (Maior and Standard) models.

The Pirelli MAIOR model had the largest shells and were double-walled. Among the shells was a bellows-shaped rubber sheet, which was fastened in the furrows of the shells by metal clamps.



The Pirelli Explorer Maior and Explorer Standard versions had the same first stage that reduced cylinder pressure to an intermediate pressure of 43 PSI.

The Minor Explorer was the later version created in 1960. This model already features the shells in the rounded format.



The stainless steel cable was attached to the regulator mechanism on the top cover (regulator lever) and was placed through the hose for an adjustable fit on the mouthpiece. The exhaust valve was nothing more than a screw with a rubber washer and the cable connected.

The Pirelli Explorer regulator was imported and distributed in the United States by the company Sport-o-Mation from Los Angeles.



In 1968, PIRELLI stopped the production of diving equipment for the Italian Navy.




1. http://history.flyer.it/rebreathers/Italiano/sezioni/storia/frameset.htm

2. HDS NOTIZIE N. 34 - Settembre 2005 - http://www.hdsitalia.com/

3. http://www.omg-italy.it/uk/storia.html

4. Historical Diver Magazine #31 - Pirelli Explorer by Kent Rockwell


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