Rebreathe Deep the Gathering Doom

How did a careful, experienced dive instructor find himself 200 feet underwater off Hallandale Beach with no way to survive?

Not everything about his young life was ideal, however. During his senior year in high school, Zak's mother succumbed after fighting cancer for more than a year. His 14-year-old sister ran away from home soon after. If it tore him apart, Jones didn't let on. He advised his father to buy a boat and sail the world.

After high school, he attended some community college classes but never graduated. School wasn't his thing. In the dive shop — that's where he excelled.

At 18, he became one of the youngest dive instructors in the State of Washington, and that was about the time his father also got certified to dive.

"It was either that or I wouldn't see him," he says. And his son was the kind of guy everybody wanted to see.

Jones had the answer to every question and was willing to spend hours with dive shop customers. But he also earned the nickname "Sea Biscuit," because he was always raring to go.

Diving with Jones was fun, but it was also safe. Divers who knew Jones insist he was meticulous. He had trained other instructors. He certainly knew the dangers.

But he was also a risk taker. Jones had dived subterranean caves, deep wrecks, and other challenging sites all over the world — the South Pacific, the Yucatan Peninsula, Alaska's Kodiak Island, the Mediterranean Sea, Belize, the Sea of Cortez, and more. He was part of a dive team that recovered a Boeing B-17 in Labrador, Canada, and had been on 500-foot dives — far more challenging than Tenneco Towers.

And like other hardcore types, he was particularly fond of a piece of equipment that allows divers to stay down longer and makes the bubbling undersea adventures of traditional scuba divers like Jacques Cousteau look like swimming in the kiddie pool.

Zak Jones, in other words, was a rebreather man.

There are claims that the rebreather was invented earlier, but the first person who clearly understood what he was doing — breathing and rebreathing the same air underwater — died after using his device for only 20 minutes.

The year before, in 1771, a British man named John Smeaton had attached an air pump to a diving bell for the first time. But in France, inventor Sieur Freminet took a different approach: Rather than simply expel the air that he would be breathing, he rigged his equipment so that what he exhaled came back into his apparatus.

What Freminet apparently didn't understand, however, is that the air we breathe out and the air we take in have different compositions. Within just a few minutes underwater, Freminet was poisoning himself with his own exhalations. The culprit: carbon dioxide.

On land, the carbon dioxide we exhale is harmless; it dissipates into the air around us and is absorbed by plant life. But in a confined space, without proper ventilation, the carbon dioxide we produce can quickly build up and become toxic.

For Cousteau and his partner Emile Gagnan developing the Aqua-Lung during World War II, there was an easy solution to this problem: Don't rebreathe. Earlier inventors had designed self-contained diving units, and others had developed the crucial on-demand regulator that allowed air to be taken from tanks only when a diver needed it. But Cousteau and Gagnan were the first to combine all the best features in an apparatus that allowed for the kind of unfettered underwater exploration that became associated with the Cousteau name.

To this day, the most popular way of exploring the sea is still based on Cousteau's model: compressed air in tanks worn on the back of the diver, delivered with the use of a regulator that expels exhalations in a cloud of bubbles. How long a diver stays down depends upon how long the supply of air lasts.

Careful dives, however, require slow transitions to deeper water and slow ascents. That time eats into the supply of air. And the bubbles that divers exhale, while useful for expelling carbon dioxide and other unwelcome gases, can scare away undersea life.

Not to mention the precious oxygen those bubbles waste. Although oxygen makes up about 21 percent of air, human lungs make very inefficient use of it. Not only do we exhale carbon dioxide but nearly all of the oxygen we breathe in goes right back out again. And for divers, that means that most of the oxygen they need underwater gets wasted in the bubbles they send to the surface.

For those reasons and more, the concept of rebreathing — of reusing the air that comes from the lungs — never went away. As early as the 19th Century, inventors were aware that they could reuse the precious oxygen in a diver's apparatus only if they came up with a way to absorb the carbon dioxide in a closed system.

In the 1930s, Italian spear fishermen were having luck with a system that filtered exhalations through soda lime, a caustic, white, powdery substance made from quicklime that had been treated with lye. That technology became popular in World War II with frogmen who wanted to dive without releasing telltale bubbles to betray their location.

Soda lime filters and scrubbers made from a similar compound, lithium hydroxide, have become standard equipment in closed breathing systems ever since — such scrubbers keep air breathable in submarines and spaceships, for example, and the military is still the rebreather's best customer. In the past decade, however, commercial rebreathers have grown dramatically in popularity with serious recreational divers.

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