Oxygen is the only gas we breathe that supports life. In the air, a normal concentration of oxygen is 21%, while the rest of the atmosphere is made up of 78% nitrogen and trace gases.

Inert gases such argon and helium, as well as nitrogen, are not toxic, but they do not support human breathing and reduce levels of oxygen in the air. They are odourless, colourless and tasteless making them undetectable.

An increase in the concentration of any other gases that are not oxygen can lead to a situation where individuals are at risk of asphyxiation which can cause serious injury or even death. This removal of oxygen gas in the air we breathe makes having an oxygen depletion sensor not just useful, but essential to maintaining life.


Despite the risk of oxygen depletion, the use of inert and speciality gases is widespread in several industries and processes. This includes:

Medical – In the medical industry they use inert and speciality gases in cryopreservation, tissue preservation and cancer treatment.
Laboratory – Laboratories use multiple inert gases such as argon, nitrogen and helium as carrier gases and also in cryogenics.
Commercial diving – Commercial and saturation divers use a heliox mix, which is a breathing gas composed of oxygen and helium.
Beverage and Hospitality – Nitrogen is used to dispense beverages such as beer, and also prevent oxidation which can affect taste and quality.
Forestry – Gases such as phosphine (PH3) are commonly used to fumigate timber and other agricultural products prone to infestation.
Horticulture– Nitrogen is used in the Controlled Atmosphere Storage (CAS) of produce including apples, pears, grains and legumes to keep food fresh and prevent decay.
Food packaging and storage – Nitrogen is used in both the packing and storage phases of products such as cooked meats, dried foods, fresh produce, fruits and vegetables.

These industries highlight the necessary need for oxygen depletion sensors in order to maintain the safety and well-being of people.

Poorly ventilated areas and confined, restricted or enclosed spaces usually have an oxygen-deficient atmosphere. Low oxygen levels can also exist in ‘open areas’ including areas with ventilation, laboratories, buildings and outside near equipment.


The body’s oxygen transport system takes oxygen to the working muscles through the circulatory and respiratory systems working together. When we breathe, oxygen enters the lungs and is absorbed into the bloodstream to fuel the cells in our bodies. If the level of oxygen concentration falls below the normal rate, it can cause damage to a person’s health.

Depending on the concentration of oxygen, the effects and symptoms of oxygen depletion on the human body will vary. At 19% people may suffer some physiological effects, but it may not be noticeable; while a drop to 12-15% is enough to cause poor judgement, faulty coordination, abnormal fatigue and emotional upset. If the oxygen level reaches less than 10% this can cause immediate fainting, an inability to move, loss of consciousness and as previously mentioned, death.


The only way to detect low oxygen concentrations is with real-time monitoring from the use of continuous oxygen depletion sensors.

Analox provide two different oxygen depletion sensors which have been designed for industries including saturation diving, commercial diving, laboratory and beverage and hospitality.

The O2NE+ O2 monitor is designed to detect the presence of low oxygen in ambient air.

The Safe-Ox+ O2 monitor is designed to detect the presence of high and low levels of oxygen in ambient air. High levels of oxygen can be just as dangerous as low levels.

Both monitors provide a digital readout of oxygen, plus audible and visual alarms to potentially dangerous deficiencies (and increases in case of Safe-Ox+) of oxygen in the air surrounding the instrument.

The O2NE+ room oxygen sensor provides two audio-visual alarms which are pre-set at 19.5% and 18% to warn personnel of a potential leak that may cause the Olevels to deplete to a dangerous level. The Safe-Ox+ oxygen enrichment and depletion monitor has two pre-set alarm levels at 23.0% and 19.5% O2 .  However, both products can be adjusted to trigger an alarm at a different level of oxygen concentration.

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