Technology丨Three Small Steps To Make Nitrox Diving Safer


Over the years, nitrox diving has brought many benefits to divers, including longer stagnation time, shorter surface rest time, increased number of repetitive dives, and so on.

However, things are always good and bad, sometimes worse. Due to the increase in r, nitrox diving has brought about the limitation of diving depth and other problems. A common misconception is that these high oxygen levels are good for deep dive divers while diving.

When we use nitrox diving, it is recommended to use the most important three steps below to best prepare and plan for your dive.

1. Gas analysis
2. Clearly label
3. Set the dive computer

Once you follow these three steps, you can set your maximum diving depth.

Gas analysis: take your own safety in your own hands. It is entirely up to the diver, you, to confirm that the high oxygen concentration of the cylinder will be used. Because each high-oxygen cylinder has a different concentration and therefore has a different maximum diving depth (MOD), you need to make sure that the maximum depth of the cylinder and the oxygen partial pressure are within a safe range. Many experienced Nitrox divers use a partial pressure limit of 1.6 in calm and warm waters, but lower the partial pressure limit to 1.4 in colder or complex environments.

Once your cylinder is filled, the filling staff will check the oxygen partial pressure of the cylinder – we recommend that you be there to confirm it – or you can check it yourself. Both of these methods are acceptable, allowing you to confirm that your cylinder is using the correct gas mixture, because in the end, this will be the cylinder you want to use.

Clearly label: To complete this procedure, make sure the cylinder is marked with the filling date, oxygen concentration, maximum diving depth, oxygen partial pressure limit, the name of the user and the name or initials of the gas analyzer. Your signature means that you have confirmed that the cylinder has been received correctly and that the cylinder contains the correct proportion of filling gas.

It is important to analyze each cylinder to be used and mark the amount of mixed gas one by one. Although the importance of repeated reiteration seems to be redundant, we all know that Nitrox divers often get the wrong cylinder for diving because there is no such indication or for analyzing the gas cylinder mixture. You need to know the ratio of mixed gas in your tank before diving, so that you can plan your dive adequately and set up your dive computer to avoid accidents.

Setting up the dive computer: Before each nitrox dive, you must check that the nitrox setting of your dive computer is set correctly. This action is very important. Remember that there are two settings that must be remembered, one is the oxygen concentration setting, and the other is the maximum oxygen partial pressure limit setting. Remember, some dive computers are set to use “FO2” (oxygen concentration). In other words, in this case, 32% oxygen is equivalent to an oxygen concentration setting of .32.

Although different dive computers have different default settings for oxygen concentration and maximum oxygen partial pressure limit, most of the default values are biased towards conservative settings. In many situations, the preset oxygen concentration percentage is 21%, and the preset maximum oxygen partial pressure limit is set at 1.4. If you do not check these settings again and adjust these values correctly according to the dive plan, you will not be able to fully get the benefits of using Nitrox with the correct dive computer settings.

Ok! Now you know how to plan your maximum dive depth and lag time. If you always remember to analyze, label, and correctly set up your computer, based on your gas mixture ratio and your diving plan, then you are ready! Finally, remember! When using Nitrox diving, do not dive deeper than your maximum diving depth (MOD).

Do you remember that when you went to OPEN WATER, the instructor might be discussing the theory of decompression. When introducing the specialty diving course, did you mention the term Nitrox? What is Nitrox diving? What are the benefits? Today’s Q&A will briefly introduce NITROX diving.

What is nitrox diving

NITROX diving is also known as Enriched Air Nitrox (EAN). EAN refers to mixed air with an oxygen ratio higher than 21%. The general air-oxygen ratio is close to 21%, which means that the oxygen ratio of the mixed gas is higher than 21%, and the relative nitrogen ratio is less than 79%. The reduction in the ratio of nitrogen means that the nitrogen absorbed by the body at the same depth is reduced.

In recreational diving, the most common myth about hyperoxia is that hyperoxia can make you dive deeper and longer. But the actual situation is that Nitrox is a gas that is more suitable for shallow water diving than air. It allows divers to have a longer no-decompression limit than divers who use air at the same diving depth and reduces decompression sickness. There are many advantages such as the possibility of nitrogen anesthesia, shortening the decompression time and the interval of repeated diving.

What are the benefits of using Nitrox diving?

Looking back on the OPEN WATER course, the coach repeatedly reminded that excessive nitrogen absorption is dangerous. When the body absorbs excessive nitrogen, which may cause the body to be unable to remove the excessive nitrogen in the body during the normal ascent process, it is necessary to perform a decompression procedure, but decompression diving is not recommended for general recreational diving. Therefore, when diving with Nitrox NITROX, the absorption of nitrogen is reduced, so that divers can have more no-decompression time within the depth limit, and also have more time to enjoy the beautiful scenery in the water and improve the safety of diving.

The author first felt the power of NITROX in Key West, Miami in 2000. I remember that the boat dive that morning was a 30-meter shipwreck, and the two dive partners on the same boat used yellow-green high-oxygen cylinders. At that time, I did not pay special attention. When I followed the dive line to reach the target depth (about 27 meters), the no-decompression time displayed by my ALADIN meter was 19 minutes, which was great for that day’s high visibility and sinking ship. To my shock, the 19-minute dive time is quite limited. Soon, the fellow divemaster told us to ascend slowly and make a safe stop. Our group of potential friends who use normal air slowly rose to 5 meters for a safety stop. The visibility at the time was great (about 30 meters). At the depth of the safety stop, I could clearly see the ship lying still. The Spanish fishing boats on the bottom of the sea, the two NITROX cylinders with a yellow-green appearance and the flashes they produced during photography. At that time, the feeling of psychological envy was hard to let go.

The two foreigners got on the boat about 10 minutes after we both got on the boat, and they were very happy to tell us that a large group of Jacks had just swam over, which was very spectacular. I thought that if I could stay for an extra 10 minutes, that group of spectacular jacks would not be missed.

Because the use of Nitrox NITROX has some special safety considerations, special Nitrox diving training with special expertise is necessary. These courses usually include indoor theory courses, swimming pool training and marine practice.

Most courses also cover the following headings:

1. What is NITROX?

2. NITROX Physiology

3. NITROX diving equipment

4. Plan NITROX diving

The textbook also provides NITROX decompression tables that are different from general air calculations, allowing divers to calculate the maximum diving depth and no-decompression time, and understand how to use oxygen analyzers, so that divers can measure the actual oxygen concentration in the cylinder and plan dives accurately .

When you decide to dive with NITROX, you must follow the regulator manufacturer’s instructions to determine whether this model of regulator can be used up to 40% high oxygen. The high content of oxygen is not compatible with the silicone oil of general maintenance regulators, so O-Ring and lubricating oil of the high oxygen regulator can be used. Special materials must be used to eliminate incompatibility.

Part of the regulators use special O-Ring and lubricating oil at the factory, so that they can be used for up to 40% Nitrox (some can even use up to 80% NITROX). Please pay special attention here if you buy NITROX Compatible regulator sets, please do not mix NITROX with general air bottle, because once general air is used, a small amount of hydrocarbons may remain in the regulator. Please send it to the factory when you decide to dive with NITROX again Carry out cleaning and maintenance work. Other parts, such as gas cylinders and valves, also need to use special materials and frequently clean and maintain.

Does the location provide Nitrox?

Every day, every dive site in the world has a new dive shop that provides nitrox cylinder service. More and more sightseeing dive sites, diving yachts and dive shops know that the needs of divers also see nitrox dive sites. The security and benefits brought. Next time you plan to dive, please ask if there is nitrox diving available there and how much it costs. If so, take the course first to obtain a license for hyperoxia, and then enjoy the safety and benefits of hyperoxia.

What are the disadvantages?

Although nitrox diving has many advantages, it also brings another potential threat-oxygen poisoning. The so-called “oxygen poisoning” refers to a series of pathological changes that occur in the body after a period of time when the partial pressure of oxygen in the inhaled air exceeds a certain value. It usually happens after a certain depth.