Introduction

Soon after initial problems like air-supply and protective suits were solved, divers began to experience some physiological difficulties after deeper dives and longer exposures. In fact they suffered from:

• decompression sickness
• oxygen poisoning
• nitrogen narcosis

without knowing it. This caused terrible suffering and death in the early days of diving. For many years the causes and cures for these illnesses were unknown due to a general lack of knowledge in the physical science.

Here are some names and dates of interest:

• Robert Boyle discovers the relationship between gas pressure and volume in 1662
• Daniel Rutherford discovers the gasses nitrogen and oxygen in 1772
• Paul Bert studied the effects of high and low pressures on the body. In 1878 he proposes a controlled decompression procedure to avoid the formation of gas bubbles in the bloodstream

With this knowledge around the turn of the twentieth century, it was custom to lower and raise divers very slow: only a few feet eacht minute. Even with these precautions many times problems occurred at greater depths.

John Scott Haldane did some important work in this matter. He found out that existing air pumps were not very suitable for greater depths: Due to bad ventilation of helmets carbon dioxide build up inside them causing problems for the diver. He also developed a "stage decompression" in 1905 that was accepted by the British admiralty. Haldane was the godfather of the decompression tables that we use today. 

Understanding and controlling oxygen poisoning did not go that fast. Henry Fleuss invented the first oxygen rebreather in 1876 but he did not have a clue that the gas could be very dangerous under pressure. Many trials in the years after that showed that oxygen could be dangerous under pressure. In WW II many secret military operations were carried out with oxygen rebreathers.

Nitrogen narcosis proved equally difficult to cure. Every diver was influenced by it in some degree. For many years no suitable solution to the problem was found.
In the early 1900's, compressed air diving was limited to depths less than 300 feet.

Air Recirculating helmets

In 1906 the Herr Heinrich Draeger from The Draegerwerk Company in conjunction with his chief engineer Hermann Selzner announced their latest project which was to develop diving equipment which could work without the use of a pump. The diver would carry a cylinder of compressed air or oxygen in a pack on his back. At around this time Professor Haldane was similarly working on the same subject. The principle of the equipment was to use an oxygen regeneration device which would allow the diver to use the equipment underwater without the use of a hose connected to a pump at the surface. It was really an early form of SCUBA (Self Contained Underwater Breathing Apparatus). The main problem with air recirculation was the build up of carbon dioxide generated from the expired air of the diver. This was to be removed by 'scrubbing' the air in a filter containing potash. By 1911 the first air regeneration equipment was being successfully used in smoke filled chambers and the Draegewerk factory then turned its attention to developing a system for use underwater. By 1912 whilst diving under the ice in the Baltic Sea a duration of four hours was attained.

By the end of 1912 the first commercially available hoseless equipment was available and although initially it was viewed with a degree of scepticism, reluctantly it was realised the usefulness of the equipment. Initially the equipment was suitable for depths up to 25 metres. Apart from the manoeuvrability of the diver underwater one of the main advantages was the fewer number of tenders required on the surface. For the conventional hose equipment there were typically 1 diver 2 signalmen and 4 pump men whereas using the hoseless equipment there was one diver and one signalman.

Hoseless Draeger Diving Equipment Type DM40 suitable for depths up to 40 metres.

As well as the equipment development, research had to be done on the physiological effects of recirculating the expired air. Here Hermann Seltzer and Professor Haldane came into contact with each other and along with RH Davis and Sir Leonard Hill of Siebe Gorman & Co great advances in the understanding of the diver's physiology were achieved. This work and the development of the closed regenerative equipment led to the development of the submarine escape apparatus which was used by navies around the World.

One of the main physiological problems the scientists had to overcome was the effect of Oxygen poisoning at depth greater than 20 metres and this was to be the focus of attention for several years.

The Draegerwork factory produced 2 types of equipment, The DM 20 for depths up to 20 metres using compressed oxygen for up to 3 hours and the DM 40 for depths of up to 40 metres using compressed air and compressed oxygen for 2-3 hours. The advantages were recognised over the hose equipment as follows. There was no risk of the hose becoming fouled and there were less attendants required on the surface. The divers could walk and manoeuvre himself more easily on the sea bed..

The helmet is secured to the breastplate using a 3 bolt flange which is clamped together by hexagonal bolts. The helmet is similar in design to the hose model except it has 2 extra hose fitting to the rear. The hoseless helmet may also be used as a hose model.

C1 + 2 Steel high pressure cylinders for oxygen or compressed air.

C3 Small air cylinder which also acts as a breast weight.

U1 +2 +3 isolating valves for the cylinders.

S 1 Tube carrying exhaled air.

C 4 Tube carrying fresh air.

P Canister containing potash.

d Low pressure pipe.

e + f Pressure equalising tubes.

i Injector.

m Manometer.

r Pressure reducing valve

Explaination of the working of the Hoseless Apparatus.

The Diver now is isolated from the surface and has to be self sufficient with his air supply. The apparatus has to perform 2 separate functions, one being supplying air or oxygen at a pressure suitable to sustain respiration and the second to eliminate the expired carbon dioxide from his exhaled breath.. The apparatus is contained in a back pack device which is so weighted to be portable under water. The back pack is connected to the helmet by a hose carrying expired air S1 and a hose carrying fresh air S2 back to the helmet. The expired air passes through a canister and this purifies the exhaled air of carbon dioxide. Tube S2 carries the purified air which is enriched by oxygen back to the helmet. These 2 processes are done automatically by a series of valves an an injector mechanism in the backpack.

There is little to notice about the difference between the DM 20 and DM 40 though the pressure reducing valves are different as are the contents and volume of the 2 cylinders containing either air or oxygen. In depths up to 15 metres pure oxygen may be used however this is both uneconomical and unnecessary so at shallow depths the diver breathes air and as he goes deeper this is enriched with oxygen which reduces the effect of the nitrogen . The deep diving appliance , the DM40 uses air with a small additional percentage of oxygen which is regulated by the injector mechanism . The mixing of the 2 gases is done automatically by the injector mechanism so there is no possibility of operator error providing both cylinders are opened full at the beginning of the dive.

View of an early 1920s DM 20 Backpack.	View of the pressure guage (finimeter).	View of the rear of the DM20 backpack.
Photos of DM 20 Courtesy of Andreas Koch.

Mixed Gas

In 1912, the US Navy began a continuing series of programs to expand diving technology and techniques. They experimented with gas mixtures other than air. In 1924 an experimental dive was made to 150 feet (about 50 meters) using a mixture of helium and oxygen. Substitution of helium for nitrogen in the breathing mixture produces two main effects upon the diver under pressure:

• helium causes no narcotic influence
• the absorption rate in the body is different

By using a mixture of helium and oxygen (called Heliox) the working depth is no longer limited. Heliox is now used to depths up to 1500 feet and more ! It is also the second lightest gas known. Absorption and dissolution out of the body tissues is much more rapid than that of nitrogen. This all means that a diver can go down deeper, stay there longer and have shorter deco-stops on coming up !

However, there is one problem in using Heliox: As depth increases, the danger of oxygen poisoning rises unless the amount of oxygen in the breathing mixture is carefully controlled. For this reason helium and oxygen are mixed together before the dive for that specific depth. We have a minimum amount of oxygen for any dive for the diver not to die, we also have a maximum amount for the diver not to die of oxygen poisoning !

This type of diving is called mixed-gas diving.
Breathing mixtures are classified as:

• "air" (21% oxygen , 78% nitrogen and 1% other gasses) or
• "gas" (pure oxygen, a mixture of oxygen and nitrogen or Heliox)

The US Navy played an important role in Heliox experiments: In the US there were natural gas fields of Helium. In Europe there were none. Therefore experimenting with the gas was very very expensive for the Europeans. Practically all the efforts in this field go to the United States.

U.S. Navy Deep Sea diving helmet

The US Navy developed a Mark V recirculating helmet. They started by modifying a Mark V mod 1 helmet. In the pictures below you see one of those early recirculating hats. You see that it features a banana exhaust on top. It had to be moved there because of the canister attached to the back. Some divers died using this hat: water leaked into the banana exhaust (when the diver is upside down for instance) and reached the extremely dangerous natron. I will explain that later. 

In the final design the perforated end of the banana exhaust is replaced with a second control valve. This valve looks a bit like a Chinese straw hat so it was referred to as a China Hat Model. The helmet was called the Mark V mod 4.  A  large canister was attached to the rear of the bonnet. This canister contained a carbon dioxide absorbent. Gas is supplied to the diver through a normal hose to the divers supply valve. However, the main supply valve is kept closed. Just to the side of it is a much smaller valve called a "hoke". It is attached to one side of the absorbent canister. Look at the little valve you see in each picture below. The gas supply goes from the hoke to a jet nozzle that acts as a pump to circulate the gas through the canister where carbon dioxide is removed. The fresh gas enters the helmet on the other end for the diver to breathe. Thru the nozzle a constant flow of fresh gas ventilates the helmet. The exhaust valve is normally kept close to repeatedly reuse the gas.

Have a look at the third picture, the rear view:

• the big canister holds the absorbent. On the right side you see the Hoke
• Above that from right to left you see:
•                 a gooseneck for gas-inlet in case the hoke fails or the diver wants/needs extra gas in suit and helmet
•                 the exhaust that is brought to the top of the helmet (the China Hat)
•                 a metal ring to lift the helmet of the divers head (with a steel wire for instance)
•                 the telephone inlet
•                 the inlet for the underwear heating system. The Navy developed electrically heated underwear because
                  helium takes heath from the body very fast

The Mark V deep sea helmet was the first heliox hat (for military purposes) in the world.

This DESCO deep sea diving helmet took divers to depths up to  800 feet and more! The nametag on this hat  reads "UNITED STATES NAVY DIVING HELMET MARK V MOD-1 SERIAL NO. 133 DATE OF MFG 04-47 DIVING EQUIPMENT SUPPLY CO. INC." The underside of the breastplate is stamped "NEPTUNE DIVING ACADEMY, BKLYN N.Y. 9-21-71 DISPLAY ONLY." With the date of 04-47 this must be one of the earliest hats ! (or the bonnet sits on a converted Mark V mod 1 corselet...) Natron The canister on the back was filled with Shell Natron to scrub CO2. This is the reason these helmets were never popular with divers. Shell Natron is a derivative of Lye and is extremely toxic when wet. It would burn a diver to death if it is of significant volume. This volume could be very small. This is the reason such great care was taken to ensure that the equipment had no leaks. Any small leak or moisture to the canister would cause a toxic spry that would enter the divers lungs and death was a sure thing. To guarantee a dry dive in this gear was like betting with the devil himself. To do everything to keep the water out the spitcock was removed and in the exhaust valve two non return valves were fitted to keep water out. A number of Navy divers lost that bet and died as a result of chemical burns. The U.S. Navy was the only one to use this kind of scrubber in their helmets. All the other gas hats that were produced used Soda Sorb to get rid of CO2 in air exhaled by the diver. Thanks to John Durham for his help on this part.

Kirby Commercial Helium Helmet

Yokohama Diving Apparatus Company

Somebody who bought 2 of their hats flew one over to Japan where it was copied by Yokohama Diving Apparatus Company. The boss of the firm did not even know there was an American original ! When Kirby and Morgan found out about the copy they had it tested over and over again. They made a deal: Yokohama could make and sell the helmet and Kirby Morgan would market it in the States. After The Japanese took over production the helmet was called Yokohama Diving Helmet Type - OH. It used Soda Sorb to get rid of CO2 in air exhaled by the diver . Yokohama is no longer in business. Kirby Morgan is now called Diving Industries International.
The Yokohama Helium Helmet has four Plexiglas windows, the front window screws in for the diver's comfort. To the rear of the helmet there is a first stage bail out regulator which is made by Scubapro.

Lindbergh-Hammer Helium recirculator helmet

In the mid 1960s Jon Lindbergh the son of the famous aviator Charles and his partner Mr Hammer designed the Helium recirculator helmet photographed here. They were based in Capinteria in California. The helmet's designed centered around the Toa bonnet with a large volume. The designed may have been based on the Bob Kirby helmet already in production. The side ports were modified and a scrubber canister containing the CO 2 absorbent was added to the rear of the helmet. The front Plexiglas was not removable. Communication equipment was added to the rear of the helmet. The gas control valve appears to be derived from a Victor welding torch. The builders Lindbergh-Hammer were believed at one time to have built scrubber units for the DESCO Company. At some stage DESCO manufactured one of these helmets from a Sponge helmet shell. There were only a few of these made so far we only know of five of them. Can you help with some more information or do you have one you can send a photograph of to info@divingheritage.com
Believed to be the first of the helmets produced this bears the serial number 101. There are various numbers stamped on the air inlet block indicating the serial number 1.
A close up view of the breastplate shows the serial number and the position of what we think was the TOA name badge which has been removed, the rivets having been soldered over to close the holes. An internal view shows the canister location in the rear of the helmet. Photo courtesy of Michael Tock
Here we have the helmet bearing the serial number 105 which we conclude is serial number 5. This one has the original tinning present. Again we can see evidence of a name badge once being present. Jon Lindbergh and Robert Stenuit re-enact the scene as they left the diving decompression chamber today July 6 1964. The young divers made history by living and working for two days and nights 430 feet ( 132 metres) down on the bottom of the ocean. On the bottom they breathed a gas composed of 97% helium and just 3% oxygen. The experiment proved that men can live and operate at great depths for extended periods. The decompression chamber is on the deck of the research vessel, Sea Diver. Photo courtesy of the Clint Green Collection

DESCO Commercial Helium Helmet

Stan Eike

Russian 3-bolt Helium Helmets

The Russians produced two types of Helium helmets. WKS-57 and GKS-3M.

GKS-3M

WKS-57

Related topics:

• American Diving Helmets

• Japanese Diving Helmets

• Russian mixed gas diving

• Last update: 25th November 2011