How can we make the oxygen diving more safe?

High oxygen dives bring many benefits to divers, such as longer dive, shorter water breaks, increased number of repeatable dive times, and more. However, it does not mean that high-oxygen diving is less risky and even worse than normal air diving. Due to the increased risk of oxygen poisoning, high oxygen diving brings with it depth limitations and other issues.

What is high oxygen air?

A: High-oxygen air is a mixture of nitrogen and oxygen with oxygen proportions exceeding 21% (ignoring other minor impurities). The proportion of high oxygen used in recreational diving is generally between 22% and 40%.

What is the purpose of using high oxygen diving?

A: The proportion of oxygen in the breathing mixture is increased, and the proportion of nitrogen in the mixture is reduced. In this way, the body absorbs less nitrogen under the same conditions. We can get a longer no-decompression time. The following figure shows the comparison of no-decompression time at different depths using normal air, 32% hyperoxia, and 36% hyperoxia: (meters are meters)

Does hyperoxia affect gas anesthesia?

Answer: As the depth increases, the density of our breathing gas will gradually increase, and high-density gas will have an anesthetic effect on people. Some people mistakenly call it "nitrogen drunk," but oxygen also has anesthetic effects. Among them, the anesthetic effect of oxygen is the same as that of nitrogen. So even if the ratio of the two components of the gas you breathe has changed, but your anesthetic effect has not changed, you will still produce gas anesthesia at the original depth.

Does using high oxygen require special equipment?

A: There are two aspects of high oxygen concentration that can affect your equipment:

1, high concentration of oxygen will greatly increase the damage (oxidation) speed of some parts of the equipment.

2, high concentration of oxygen is a highly efficient combustion agent.

Our equipment will be exposed to high-oxygen components including BCD, main air supply, backup air supply, pressure gauges and cylinders.

For BCD, main air source, backup air source, pressure gauge: 40% or less of high oxygen can be used normal, more than 40% of high oxygen needs to perform oxygen treatment on the parts of these equipment, such as the use of anti-oxidation seal Rings and lubricants and so on.

For gas cylinders: Since most high-oxygen cylinders use a mixing method when they are filled, they first hit a fixed amount of pure oxygen into the intake bottle, and then use a special oxygen-enriched compressor to drive into the air, diluting the pure oxygen to the level we want. The desired concentration. When filling with this method, when the pure oxygen is first introduced into the cylinder, there will be high temperature inside the cylinder, plus the combustion effect of pure oxygen. At this time, if the cylinder is slightly flammable impurities, the cylinder will explode. Therefore, as long as it is 22% or more of high oxygen, special high-oxygen bottles must be used. It is forbidden to mix ordinary and high-oxygen bottles. If you inadvertently use normal air compressors to inflate the high oxygen cylinders, you must have a professional to clean the cylinders before filling with high oxygen.

How to distinguish between high oxygen cylinders and ordinary air cylinders?

A: The position of the upper part of the high oxygen bottle will surround a circle of 15 cm wide stickers. The upper and lower edges of the sticker are yellow, 2.5 cm wide, and the middle 10 cm is green. They are written in white or yellow fonts: Nitrox or Enriched Air. Or Enriched Air Nitrox.

How much does the high oxygen percentage play when diving?

A: PADI's High Oxygen Air Diver course allows you to use 22% to 40% hyperoxia. The two commonly used ratios are:

Ean×32, also became NOAA Nitrox I

Ean × 36, also became NOAA Nitrox II

What is the partial pressure of oxygen?

A: The partial pressure of oxygen is the pressure provided by the oxygen portion of the mixed gas. The calculation method is as follows: Oxygen partial pressure = total pressure x percentage of oxygen.

For example, under atmospheric pressure at sea level, the oxygen partial pressure of normal air is:

Oxygen partial pressure=1bar×21%=0.21bar

Under water 30 meters, 32% oxygen partial pressure of oxygen is:

Oxygen partial pressure = 4bar × 32% = 1.28bar (1bar pressure per 10m seawater, plus 1bar atmospheric pressure in Shanghai plane, so 30m total pressure is 4bar)

The maximum oxygen partial pressure that the human body can accept is 1.4bar. When the oxygen partial pressure of the breathing gas is greater than 1.4bar, it may cause neurological oxygen toxicity and lung oxygen poisoning. Oxygen poisoning of the nervous system can cause divers to cramp. The cramps themselves are harmless, but in all likelihood, the cramping in the water will cause the diver to spit out the regulator and paralyze. Oxygen in the lungs is because oxygen at high partial pressures is highly corrosive (chemically called oxidative) and will corrode our alveoli for a long period of time. Symptoms include inflammation of the lungs, burning sensation in the chest, cough, and vital capacity. cut back.

What should I do when I find my own aerobic poisoning?

A: Immediately increase at normal speed, skip the safety stop and end the dive.

How to avoid oxygen poisoning?

A: Before using high oxygen diving, you must personally measure the oxygen percentage with an analyzer. Remember! It is your responsibility to measure the oxygen concentration in your high oxygen cylinder and cannot allow others to do it. After measuring, set your computer's watch to high oxygen mode and input your own oxygen ratio.

Use the following formula to calculate the depth limit of your use of high oxygen:

Depth limit = (1.4 ÷ percent oxygen tested - 1) × 10

This formula consists of:

Oxygen partial pressure = total pressure x percentage of oxygen

Total pressure = depth ÷ 10 +1.

Set the computer to near this depth to alert.