Wednesday, November 23, 2011

Women and Diving


There are two answers to this important question. The short answer is "no." Much has been written about the difference between men and women divers, and no self respecting dive columnist would stop with such a simple answer. But the fact is, the differences between men and women regarding scuba diving are, with one exception, minor and not significant. The one exception, of course, is pregnancy, which I will discuss in a later question.

The long answer is that women, on average, have smaller lungs, a lower aerobic capacity, a greater percentage of body fat, and less upper body strength than men, and these differences have some effects on diving. Women tend to use less air/minute than men (because of their smaller lung volume), but in recreational diving that is rarely an important factor. Women may not have the same capacity for extreme physical exertion as men, but that too is of little consequence in recreational diving. Since women have a higher percentage of body fat in men, in theory they should have better tolerance to cold water. Although some think the higher percentage of body fat increases the risk of DCS, there is really no solid evidence to support this belief (discussed below).

The long answer also recognizes that the menstrual period poses some concern for women, but this is not ordinarily a limitation. The long answer must also include the observation that men as a group seem to take more risks than women, and as a result show up more frequently in mortality statistics associated with cave, deep, and mixed gas diving.

However, except for pregnancy, the anatomic differences between men and women are simply not a big deal when it comes to scuba diving. Either sex can learn to become quite proficient both as a recreational diver or as a scuba diving professional.


Women have on average 10% more subcutaneous fat than men. Since fat tissue can hold five times more nitrogen than blood, it has been suggested that women might be more susceptible to decompression sickness (DCS) than men. However, the few studies in this area are inconclusive. Some studies have suggested an increase in DCS among women, while others have not found any difference. If you read the literature on the subject there appears to be "some controversy"; however, I believe this merely reflects that the data are insufficient to show a difference one way or the other. Not controversial, of course, is the risk of DCS simply from diving. Women need to be every bit as cautious as men in this activity. Until some respected agency comes out with a different set of dive tables for men and women, it is safe to assume the risk for DCS is the same or about the same, and not worry about it.

As for the other component of decompression illness arterial gas embolism there are no reports of an excess incidence in women. Also, the incidence of patent foramen ovale (a theoretical predisposition to arterial embolism) is the same in women and men.

Overall, women do not seem over-represented in DAN's yearly compilation of diving accident statistics. Of course, the great unknown (as with many other diving accident statistics) is the number of people at risk. Personal experience, as well as the vast panoply of scuba literature, suggest as many women as men enjoy recreational diving.

When scuba first became popular there were very few women divers (Jacques Cousteau's wife Simone was probably the very first, in the 1940s). Now, about half of newly-certified divers are women. There is nothing in scuba instructors' collective experience to indicate that women have a greater risk than men for developing decompression illness.

In summary, inconclusive studies, as well as lack of any perceived gender-related problems by professionals in the field, suggest there is no increased risk of DCS and AGE among women divers.


As already mentioned, men on average seem to take more risks than women. Apart from this observation, which may account for the disproportionate number of men who engage in technical (as opposed to recreational) diving, there seem to be no important psychological differences between men and women that would affect scuba diving.


Again, there are no conclusive studies to answer this question. Repeated exposure to hyperbaric pressure has not been shown to affect hormone regulation, ovulation, or menstruation.

Many women are concerned that menstrual bleeding itself could attract sharks or other predators. However, with tampons this is simply not a problem. It is not even clear that it would be a problem without a tampon; the amount of blood that would be released into the water from menstruation during a 30 or 45-minute dive is minuscule. Some women have experienced a greater menstrual flow when diving, but this has not posed any significant problem either. Thus, it appears safe to dive during the menstrual period providing, of course, the woman feels healthy. Obviously any woman who suffers severe menstrual cramps, headaches, or other symptoms related to her period should refrain from diving until fully recovered.


There are no data to indicate that use of oral contraceptives increases risk of diving accidents. We know that oral contraceptives and smoking increase the risk of stroke, but smoking is bad for divers in any case. Oral contraceptives have also been associated with increased rates of blood clotting ("thrombo-embolic" disease) and mild hypertension, particularly in women over age 35. However, if oral contraceptives cause the woman no problem on land, there should be no problem under water.


A short exposure to increased ambient pressure, per se, appears of no consequence to the fetus. However some studies on pregnant animals have shown an increased rate of fetal abnormality from decompression sickness, particularly among sheep; different studies in other animals have not shown an ill effect on the fetus. Like many other medical conditions, the available studies on this issue are inconclusive.

Based on what is known about pregnancy, and about diving, my recommendation (and that of most physicians) is that pregnant women should not dive. There are three reasons for this blanket recommendation. First, pregnancy is only nine months, a relatively short period in one's life; it is simply not worth taking any unnecessary risks by subjecting the unborn child to an abnormal environment. The body experiences marked pressure changes under water, changes that are believed to be safe for adults who follow recreational guidelines. However, considering that accidents do occur, diving is riskier than not diving. We have so little information about decompression on the developing fetus, and much of the information is conflicting, that common sense suggests any risk is simply not worth taking.

The second reason against diving while pregnant has to do with treatment of diving injuries. If a pregnant diver does develop DCS or gas embolism, she will be referred for hyperbaric therapy. Hyperbaric therapy poses a theoretical risk to the unborn child, because of the high oxygen pressures. The developing eye of a fetus is particularly prone to oxygen toxicity. Although non-diving pregnant woman have been successfully treated with hyperbaric therapy (for carbon monoxide poisoning), there is always concern a fetus could be harmed, especially if multiple treatments are needed.

It has been recommended by some authors that pregnant women who do dive stay shallower than 33 feet (less than 2 atmospheres total); the rationale is that shallow diving should at least prevent any risk of the bends. However, there are no data to support this recommendation, and a sensitive fetus might not like any increase in nitrogen or oxygen pressure. Certainly the risk of air embolism is not diminished by staying shallow.

The third reason against diving is that pregnancy is often accompanied by changes which could make a dive uncomfortable, if not downright hazardous. These changes include frequent bouts of nausea ("morning sickness"), gastric reflux (from the enlarged uterus), and discomfort from increased abdominal girth. In theory a woman could become nauseous on the dive boat (abetted by any sea sickness), experience regurgitation under water, and then lose her weight belt as she tries to adjust it for her larger size all on one dive!

In summary, it is a strong recommendation that any woman who is pregnant (or thinks she may be, or is trying to become) refrain from diving.


I would leave this decision up to the woman and her obstetrician. The answer should depend on how quickly the woman has regained her strength, whether the delivery was vaginal or by C-section, whether there are any post-partum complications, etc. A general recommendation is that the woman should be able to return to diving when she feels back to her baseline health and has medical clearance to resume strenuous activity.


Although diving during pregnancy is definitely not recommended, on occasion a woman may dive without knowing she is pregnant (i.e., very early in gestation). This event should not be cause for alarm. There is certainly no evidence to warrant pregnancy termination because the fetus was briefly exposed to higher pressures. However, if the dive was complicated by injury to the woman, then the specifics of the case need to be discussed with the diver's obstetrician and, if necessary, a dive medicine specialist.


Ideally, no. The stereotype of a weak, mechanically disinterested, and/or uncoordinated female is out of date and harmful to both sexes. Any woman who expects manual chores will be done for her (carrying her tank, attaching the regulator, etc.) because she is a woman, loses the opportunity to learn important skills and remain self-sufficient. Any man who abridges a woman's chance for self-sufficiency by insisting on doing things for her not only demeans her but also perpetuates an outdated stereotype. Also, if the woman is his dive buddy, he may weaken skills she may one day need to help him.

Scuba diving is a level playing field; it is no place for machismo behavior or sexism of any sort. Equality certainly reigns at the professional level. Hundreds of women instructors teach open water and advanced courses to men and women. Women run dive shops, operate dive boats and lead diving expeditions. Resorts that carry tanks, attach BC's or perform other dive-related chores for its customers do so for men and women alike. Obviously, scuba diving is no longer "a man's world" as it was perhaps a generation ago. Today, it should be as acceptable for a man to ask a woman for help with equipment or some other problem, as vice versa. When diving, women and men should want and expect to be treated as equals.


Kathy Dowsett

Friday, November 18, 2011

Former carpenter immerses himself in his new job

College program leads to unique career option

A downturn in the construction industry in the late 1980s led Shaun Kerr to new waters, literally, as he now dives to work every day.

While laid off after three years of carpentry work, he discovered an underwater commercial diving program at Seneca College.

“It’s a good profession for me ... it’s exciting and challenging,” the 41-year-old says, in a telephone interview following a day out on Lake Erie.

Kerr explains that commercial diving involves working on “virtually any structure in the water.”
These days, as a commercial diver for Talisman Energy Corp., he works primarily on the natural gas wells in Lake Erie. However, he’s worked on many underwater projects, including the Confederation Bridge in Prince Edward Island, power plants, water intake systems, and salvage operations.

“One of the attractions (of the job) is you go wherever you want ... you can work all over the world,” Kerr says. He adds the Seneca program is recognized worldwide. With his training, he’s certified to dive to depths of 165 feet. But Kerr can plunge deeper, thanks to additional training he received in Scotland.

Because his contract with Talisman is from the spring until the end of October, Kerr can do contract diving jobs the rest of the year. A couple of years ago, he worked in Japan for five months salvaging a ship carrying 3,500 vehicles, which was damaged in a typhoon.

The Toronto man has also worked in Indonesia, China, Singapore, Taiwan, Finland, New Zealand, Chile and the Dominican Republic. Some of that work involved constructing and repairing pipelines, or working alongside remotely-operated vehicles, which are sometimes used for underwater filming.

Last year, he worked up north at the Bruce Power plant for the winter. Inspections and repairs at the power plant meant diving under five feet of ice.

Kerr is attracted to the personal challenge of the job, but admits there are some pitfalls. It’s hard on the family life when you’re constantly travelling and the seasonal hours are long.
And Kerr admits, as he gets older, he’s becoming less tolerant of the cold.

It’s also “inherently dangerous,” Kerr says. “You’re working with cranes and things can happen when you have limited visibility,” he says. “Little accidents on the surface can be tragic in the water.” Although every effort is made to ensure safety on the job, Kerr says he’s had some “close calls.

“You really rely on the guys on the surface to look out for your well-being,” he says, adding you trust them with your life.

And it’s a slow job, as Kerr compares it to “working with oven mitts on and turning off the lights.” They wear three-fingered mitts, making it difficult to pick up a half-inch bolt or other small piece.

In recent years, cameras have been installed on the divers “so those on the surface can watch everything being done.”

He says it helps ensure everything is properly inspected because it’s so costly to have to go back and redo an underwater job.

Ross McPhee, a production diver with Talisman, says it aids in training new divers. “We can accelerate the training and can help keep someone from making a mistake,” he says.
The 30-year-veteran of commercial diving says the job is more than just diving.

“Diving is the way I get to my work,” he says, adding he oversees the underground gas field on the Canadian side of the water, comprised of more than 100 natural gas wells and thousands of miles of pipeline from Port Colborne in the east to Wheatley in the west.

“It’s a good profession for me ... it’s exciting and challenging.” Shaun Kerr
commercial diver.

As the supervisor, McPhee says there’s a lot of equipment to install, maintain and pressure hoses to check. He notes that each valve is now computerized, but the computer systems have to be installed and programmed and it’s the divers that do that work. At times, there’s also drilling to be done.

McPhee also schedules the divers who go out in teams of five or six on the vessels or rigs to do the necessary work.

The 52-year-old has spent his entire career in Lake Erie – during that time he’s seen vast improvements in technology and safety.

He studied math and science at university, taking the diving program at Seneca as a reprieve from university. But he was offered a job after graduating from the diving program and never returned to school.

Personally, McPhee said he’s never gotten over the thrill of the first dive of the day, adding, “I hope I never will.” While he sacrifices family time during diving season, the Dorchester resident tries to make up for it during the off-season, opting not take any offshore jobs.
He says there’s a worldwide market for commercial divers, especially after major tragedies such as Hurricane Katrina. In Ontario alone, he said there are a number of jobs — virtually any place that has a shore requires a diver to go under at some point for inspections, maintenance and repairs.

Sean O’Dwyer of The Carpenters Union Local 785 in Cambridge has represented the commercial divers in Lake Erie for the last four years.

He says The Carpenters Union, which began representing divers about 40 years ago, now represents about 70 to 80 divers across the province.

He says commercial divers are also involved in aiding the Department of Transportation in inspecting ships and freighters.

Unionization, he says, has helped to ensure they have more competitive wages, benefits, pension and for those who choose, the opportunity to apprentice as a carpenter so they have options for their future when they can no longer handle the physical demands of diving.

Kathy Dowsett

Wednesday, November 16, 2011

Scuba Diving::::Is It An Extreme Sport?

How extreme do you want your sport to be?

What is your comfort level with risk?

When it comes to scuba diving, these are questions you will have to ask yourself if you wish to advance to some of the more extreme elements of the sport.

That is one of the strengths of scuba. It’s versatile. You can choose the level at which you wish to participate.

“Scuba is not extreme, but it lends itself to extremes,” says Catherine Donker, a dive master from St. Thomas, Ontario, Canada. “It is user friendly. You can take a casual approach if you are not looking for a lot of physical challenge or excitement. You can choose dives according to your level or interest. You can do 15-to-20 foot dives on top of a reef or if you’re getting into the extremes, a wreck such as the Andrea Doria.

While approaching the coast off Nantucket, Massachusetts, the Andrea Doria and the eastbound freighter MS Stockholm collided. The Andrea Doria sank on July 26, 1956, resulting in 46 deaths. Diving to its wreck is difficult and dangerous and it involves depths beyond 200 feet. It is only for highly qualified technical-certified divers, whose certifications include training in the use of mixed gases.

For scuba divers who want to push the limits in other ways, there is cavern and cave diving.

PADI describes the cavern zone as the area near the entrance of a cave where natural light is always visible. Cavern divers always keep the entrance in sight and use a guideline to help them find their way back in case they lose sight of the entrance. However, cave divers will go much farther into the cave, sometimes thousands of yards.

The majority of scuba enthusiasts will probably never want to advance to cave diving. They are happy with what they set out to do – explore the underwater world of coral reefs and occasionally dive to a shipwreck that is accessible enough for the dive certification they hold.

There is no shortage of sites for either experience. Florida and the Florida Keys are popular destinations for people living on or near the U.S. Eastern seaboard.

“The Keys has both wrecks and reefs covered,” says Catherine. “There are hundreds of wrecks in Florida.”

Dive sites include the USS Oriskany, a former aircraft carrier that was sunk off Pensacola, and the USS Spiegel Grove, a former U.S. Navy dock loading ship that rests on the bottom offshore from Key Largo. Both of these dives can be done with an Advanced Open Water certification.

Viewing reefs and shipwrecks is more in line with what most divers envisioned when they began scuba lessons.

“I would say the most common reason people enrol in lessons is a reference from a friend. They’ve heard exciting stories of the incredible colours of the reefs and amazing aquatic life or maybe a compelling historical wreck,” says Catherine. “If you can get them to watch your video creations, people see what they’ve only seen before on National Geographic and they know that it really is accessible to anyone. They know you are not Jacques Cousteau, just a regular person.”

Kathy Dowsett

Sunday, November 13, 2011

SS Andrea Doria


SS Andrea Doria[p] was an ocean liner for the Italian Line (Società di navigazione Italia) home ported in Genoa, Italy, most famous for its sinking in 1956, when 46 people died. Named after the 16th-century Genoese admiral Andrea Doria, the ship had a gross register tonnage of 29,100 and a capacity of about 1,200 passengers and 500 crew. For a country attempting to rebuild its economy and reputation after World War II, Andrea Doria was an icon of Italian national pride. Of all Italy's ships at the time, Andrea Doria was the largest, fastest and supposedly safest. Launched on 16 June 1951, the ship undertook its maiden voyage on 14 January 1953.

During the ship's maiden voyage, it encountered heavy storms on the final approach to New York, listing a full twenty-eight degrees. Nevertheless, Andrea Doria completed its maiden voyage on 23 January only a few minutes behind schedule, and received a welcoming delegation which included New York Mayor Vincent R. Impellitteri. Afterwards, Andrea Doria became one of Italy's most popular and successful ocean liners as it was always filled to capacity. By mid-1956, it was making its 100th crossing of the Atlantic.

A collision course

On the evening of Wednesday, 25 July 1956, Andrea Doria, commanded by Captain Piero Calamai, carrying 1,134 passengers and 572 crew, was heading west towards New York. It was the last night of a transatlantic crossing from Genoa that began on 17 July: the ship was expected to dock in New York the next morning.

At the same time, MS Stockholm, a smaller passenger liner of the Swedish American Line, had departed New York about midday, heading east across the North Atlantic Ocean toward Gothenburg, Sweden. Stockholm was commanded by Captain Harry Gunnar Nordenson, though Third Officer Johan-Ernst Carstens-Johannsen was on duty on the bridge at the time. Stockholm was following its usual course east to Nantucket Lightship, making about 18 knots (33 km/h) with clear skies. Carstens estimated visibility at 6 nautical miles (11 km).

As Stockholm and Andrea Doria were approaching each other head-on, in the heavily used shipping corridor, the westbound Andrea Doria had been traveling in heavy fog for hours. The captain had reduced speed slightly from 23.0 to 21.8 knots (42.6 to 40.4 km/h), activated the ship's fog-warning whistle, and had closed the watertight doors, all customary precautions while sailing in such conditions. However, the eastbound Stockholm had yet to enter what was apparently the edge of a fog bank and was seemingly unaware of it and the movement of the other ship hidden in it. (The waters of the North Atlantic south of Nantucket Island are frequently the site of intermittent fog as the cold Labrador Current encounters the Gulf Stream.)

As the two ships approached each other, at a combined speed of 40 knots (74 km/h), each was aware of the presence of another ship but was guided only by radar; they apparently misinterpreted each other's course. There was no radio communication between the two ships, at first.

The original inquiry established that in the critical minutes before the collision, Andrea Doria gradually steered to port, attempting a starboard-to-starboard passing, while Stockholm turned about 20 degrees to its starboard, an action intended to widen the passing distance of a port-to-port passing. In fact, they were actually steering towards each other — narrowing, rather than widening, the passing distance. Compounded by the extremely thick fog that enveloped the Doria as the ships approached each other, the ships were quite close by the time visual contact had been established. By then, the crews realized that they were on a collision course, but despite last-minute maneuvers, they could not avoid the collision.

In the last moments before impact, Stockholm turned hard to starboard and was in the process of reversing its propellers, attempting to stop. The Doria, remaining at its cruising speed of almost 22 knots (41 km/h) engaged in a hard turn to port, its captain hoping to outrun the collision. At approximately 11:10 PM the two ships collided, the Stockholm striking the side of the Andrea Doria.

Impact and penetration

When Andrea Doria and Stockholm collided at almost a 90-degree angle, Stockholm's sharply raked ice breaking prow pierced Andrea Doria's starboard side approximately midway of its length. It penetrated three passenger cabins, numbers 52, 54 and 56, to a depth of nearly 40 feet (12 m), and the keel. The collision smashed many occupied passenger cabins and, at the lower levels, ripped open several of Andrea Doria's watertight compartments. The gash pierced five fuel tanks on Andrea Doria's starboard side and filled them with 500 tons of seawater. Meanwhile, air was trapped in the empty tanks on the port side, contributing to a severe, uncorrectable list. The ship's large fuel tanks were mostly empty at the time of the collision, since the ship was nearing the end of its voyage, but all the empty fuel tanks did was help the list increase.

Meanwhile, on the bridge of Stockholm, immediately after the impact, engines were placed at ALL STOP, and all watertight doors were closed. The ships were intertwined for about 30 seconds. As they separated, the smashed bow of the stationary Stockholm was dragged aft along the starboard side of the Doria, which was still moving forward, adding more gashes along the side. The two ships then separated, and the Doria moved away into the heavy fog. Initial radio distress calls were sent out by each ship, and in that manner, they learned each others' identities.

In the last moments before impact, Stockholm turned hard to starboard and was in the process of reversing its propellers, attempting to stop. The Doria, remaining at its cruising speed of almost 22 knots (41 km/h) engaged in a hard turn to port, its captain hoping to outrun the collision. At approximately 11:10 PM the two ships collided, the Stockholm striking the side of the Andrea Doria. The world soon became aware that two large ocean liners had collided.

Andrea Doria capsizes and sinks

Once the evacuation was complete, the captain of Andrea Doria shifted his attention to the possibility of towing the ship to shallow water. However, it was clear to those watching helplessly at the scene that the stricken ocean liner was continuing to roll on its side.
After all the survivors had been transplanted onto various rescue ships bound for New York, Andrea Doria's remaining crew began to disembark—forced to abandon the ship. By 9:00 AM. even Captain Calamai was in a rescue boat. The sinking began at 9:45 a.m. and by 10:00 that morning Andrea Doria was on her side at a right angle to the sea. The ship fully disappeared into the Atlantic at 10:09—almost exactly eleven hours after the collision with Stockholm took place.

22-year-old Evelyn Bartram Dudas was the first woman to successfully dive onto the Andrea Doria. Dudas reached the wreck in June, 1967; her future husband, John Dudas, retrieved the ship's compass.

As of 2010, years of ocean submersion have taken their toll. The wreck has aged and deteriorated extensively, with the hull now fractured and collapsed. The upper decks have slowly slid off the wreck to the seabed below. As a result of this transformation, a large debris field flows out from the hull of the liner. Once-popular access points frequented by divers, such as Gimbel's Hole, no longer exist. Divers call Andrea Doria a "noisy" wreck, as it emits various noises due to continual deterioration and the currents' moving broken metal around inside the hull.

However, due to this decay new access areas are constantly opening up for future divers on the ever-changing wreck. The ship lies on her side at a depth of about 250 feet in an area where the underwater weather can change suddenly from clear and calm to a ripping current filled with sediment. But the reward for those who venture this deep is to briefly rediscover a ship still recognizably the luxury liner that gaily cruised the southern Atlantic route in the 1950s. Most of the deck hardware and all three swimming pools are clearly visible. Lifeboat davits still jut from the boat deck and great cranes dominate the bow. The ship's name can still be made out on both the bow and stern.

After 20 minutes exploring the wreck, the diver must spend another 90 decompressing before returning to the surface. But he brings back with him unforgettable images of ruined luxe and of the end of a magnified era in ocean travel.

thanks to Wikipedia

Kathy Dowsett

Wednesday, November 9, 2011

Cop divers: A breed apart, a breed below

It's one of the least popular types of specialized police work: dead body retrievers.

Of the 69,200 cops in Canada, only 110 are police divers.

This week more than half of them showed up at a frozen quarry near Ottawa to train in far more favourable conditions than many of them are used to.

Ottawa rookie cop Alana Fong sits on a towel-topped, waterproof kit case with her feet propped up on a small one. Wrapped in blankets she waits in a tent for colleague Walt Leshman to surface.

The burly Newfoundlander is far more experienced; he's been a police diver for four years.

Fong is about to make her second-ever ice dive.

In fact, she's the only female police diver in Ontario and one of only a handful in Canada.

She was fast-tracked into the unit - diving has always been something that interested her - having only been hired by Ottawa Police in May.

That's because they needed her.

"There's not a lot of people that want to do this job," says Const. Brent MacIntyre, of the Ottawa Police dive, marine and trails unit.

"It takes a certain type of police officer to want to go underwater and recover human remains, so there's not a lot of pickings when we're going out to recruit new officers."

Fong's first ice dive, completed Tuesday in the quarry, was an experience she'll never forget.

"It was incredible, actually. It was quite different than diving in the summer," she says.

"Here we have a lot of visibility, when you look up at the surface you can see so many colours."

MacIntyre can speak from experience about the contrast between the visibility in a quarry and what police divers are up against diving in places like the Ottawa River.

"It's like diving in tea," he says. "You can't see anything."

The quarry near Wakefield, Que., offers 128 feet of depth and numerous underwater objects to dive to.

The divers also conducted drills and exercises with dummies.

The busiest season of the year for police divers is just around the corner - spring thaw.

Thanks to London Free Press

Kathy Dowsett

Tuesday, November 8, 2011

History of rebreathers

A rebreather is a type of breathing set that provides a breathing gas containing oxygen and recycled exhaled gas. This recycling reduces the volume of breathing gas used, making a rebreather lighter and more compact than an open-circuit breathing set for the same duration in environments where humans cannot safely breathe from the atmosphere. In the armed forces it is sometimes called "CCUBA" (Closed Circuit Underwater Breathing Apparatus).

Around 1620: In England, Cornelius Drebbel made an early oar-powered submarine. To re-oxygenate the air inside it, he likely generated oxygen by heating saltpetre (potassium nitrate) in a metal pan to emit oxygen. Heating turns the saltpetre into potassium oxide or hydroxide, which absorbs carbon dioxide from the air. That may explain why Drebbel's men were not affected by carbon dioxide build-up as much as would be expected. If so, he accidentally made a crude rebreather more than two centuries before Saint Simon Sicard's patent.

1808: The oldest known rebreather based on carbon dioxide absorption was patented in France by Sieur (old French for "sir" or "Mister") Touboulic from Brest, mechanic in the Napoleon's Imperial Navy. This early rebreather design worked with an oxygen reservoir, the oxygen being delivered progressively by the diver himself and circulating in a closed circuit through a sponge soaked in lime water. Touboulic called his invention Ichtioandre (Greek for 'fish-man'). There's no evidence of a prototype having been manufactured.

1849: Patent for the oldest known prototype of a rebreather also used an oxygen reservoir, granted to the Frenchman Pierre Aimable De Saint Simon Sicard.

1853: Professor T. Schwann designed a rebreather in Belgium; he exhibited it in Paris in 1878. It had a big backpack oxygen tank at pressure about 13.333 bars, and two scrubbers containing sponges soaked in caustic soda.

1878: Henry Fleuss invented a rebreather using stored oxygen and absorption of carbon dioxide by an absorbent (here rope yarn soaked in caustic potash solution), to rescue mineworkers who were trapped by water.

About 1900: The Davis Escape Set was designed in Britain for escape from sunken submarines. It was the first rebreather which was practical for use and produced in quantity. Various industrial oxygen rebreathers (e.g. the Siebe Gorman Salvus and the Siebe Gorman Proto, both invented in the early 1900s) were derived from it.

1903 to 1907: Professor Georges Jaubert invented Oxylithe, which is a form of sodium peroxide (Na2O2) or sodium dioxide (NaO2). As it absorbs carbon dioxide (e.g. in a rebreather's scubber) it emits oxygen.

1907: Oxylithe was used in the first filming of Twenty Thousand Leagues Under the Sea.

1907: This link shows a Draeger rebreather used for mines rescue.

In 1909 Captain S.S. Hall, R.N., and Dr. O. Rees, R.N., developed a submarine escape apparatus using Oxylithe; the Royal Navy accepted it. It was used for shallow water diving but never in a submarine escape.

1912: The first recorded mass production of rebreathers started with the Dräger rebreathers, invented some years earlier by an engineer of the Dräger company, Hermann Stelzner. The Dräger rebreathers, especially the DM20 and DM40 model series, were those used by the German helmet divers and German frogmen during World War II.

1930's: Italian sport spearfishers used rebreathers systematically. This practice came to the attention of the Italian Navy, which developed its frogman unit Decima Flottiglia MAS, which was used effectively in World War II.

World War II: Captured Italian frogmen's rebreathers influenced design of British rebreathers. Many British frogmen's breathing sets' oxygen cylinders were German pilot's oxygen cylinders recovered from shot-down German Luftwaffe planes. Those first breathing sets may have been modified Davis Submarine Escape Sets; their fullface masks were the type intended for the Siebe Gorman Salvus. But in later operations different designs were used, leading to a fullface mask with one big face window, at first oval like in this image, and later rectangular (mostly flat, but the ends curved back to allow more vision sideways). Early British frogman's rebreathers had rectangular breathing bags on the chest like Italian frogman's rebreathers; later British frogman's rebreathers had a square recess in the top so they could extend further up onto his shoulders; in front they had a rubber collar that was clamped around the absorbent canister, as in the illustration below.

Some British armed forces divers used bulky thick diving suits called Sladen suits; one version of it had a flip-up single window for both eyes to let the user get binoculars to his eyes when on the surface.

Early 1940s: US Navy rebreathers were developed by Dr. Christian J. Lambertsen for underwater warfare and is considered by the US Navy as "the father of the frogmen". Lambertsen held the first closed-circuit oxygen rebreather course in the United States for the Office of Strategic Services maritime unit at the Naval Academy on 17 May 1943.

Thanks to Wikipedia

Kathy Dowsett