As a first aid measure for divers with decompression sickness or lung over-expansion injuries, it is very effective to give them high concentrations of oxygen until they reach a hospital with a recompression chamber.

■High-pressure tanks for oxygen

Oxygen is contained in special black tanks as required by law.

The oxygen charged inside is always designated for medical use.

Tank capacities vary.

A small tank will run out of oxygen quickly, so you will need a tank at least 2 liters in size.

■Oxygen regulator (decompressor)

When breathing oxygen from an oxygen tank, a regulator is required, just as in diving.

However, the regulator used with an oxygen tank must be specially designed for oxygen.

This regulator for oxygen has a pressure gauge that indicates the remaining pressure in the oxygen tank and a dial or valve that determines the outflow of oxygen.

Some dial regulators have a window with a number showing how many liters per minute are available, while others have a separate flow meter.

These oxygen regulators cannot be lubricated with oil, silicone grease, or other lubricants to prevent ignition.

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■Types of Oxygen Masks

A mask covering the nose and mouth is required to give oxygen.

There are two types of masks: masks with demand valves and masks with reservoir bags.

●Mask with demand valve

Like a diving regulator, it allows oxygen to be breathed in only when you inhale.

The advantage of the demand valve is that oxygen does not flow when you are not breathing, thus reducing oxygen consumption.

It also allows you to breathe oxygen at 100% concentration.

●Mask with reservoir bag

This mask always has a constant flow of oxygen regardless of breathing.

With an oxygen flow rate of 10 to 15 liters per minute, it is possible to breathe oxygen with a concentration close to 100%.

This mask is often used because it requires no maintenance, but it consumes more oxygen and the tank runs out of oxygen in a short time.