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O2 Gas and its Sensor

Intro to Oxygen Gas

Oxygen gas is a chemical compound with the formula O2. It can be very difficult to detect when O2 levels are outside of regular concentrations, as it is colorless, odorless, and flavorless. Oxygen is an excellent oxidizing agent, and can either cause or intensify fires when combined with many different compounds in the atmosphere. Oxygen is non-combustible itself, but is a key part of the fire triangle that leads  to combustion of other compounds or materials.

The biggest threat oxygen poses is when there is not enough of it; oxygen deficiencies create incredibly dangerous circumstances. This makes it imperative to frequently test confined spaces for oxygen levels, so that workers are not put into vulnerable positions. Oxygen enrichment is another risk factor due to the increased chance of combustion and explosions.

Gas Characteristics

  • Colorless  
  • Odorless 
  • Insipid (tasteless)  
  • Paramagnetic (magnetizable substance) 
  • Reactive, can form oxides with all elements excluding helium, neon, argon, and krypton 
  • Moderately soluble in water  
  • CAS 7782-44-7
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Industrial O2 hazards and sources

  • Melting, manufacturing  and refining of steel and other metals.  
  • Manufacture of chemicals by controlled oxidation. 
  • Petrochemical plants and refineries.
  • Rocket propulsion.  
  • Medical and biological life support.  
  • Displacement in breweries and distilleries
  • Mining, production & manufacture of stone and glass products. 
  • Sewer and wastewater treatment.
  • Gas welding and cutting.
  • Forging
  • Heat treating 

It is generally recognized that lack of oxygen is the leading cause of death in confined spaces.

(National Fire Protection Association)

High Risk Scenarios

  • Oxygen deficiency is incredibly dangerous, particularly in confined spaces due to microbial activity (fermentation), rusting of tanks and more. 
  • Would-be rescuers are at risk since they may be unaware of an oxygen deficiency hazard at the scene of an incident involving a coworker.
  • Industrial processes that use nitrogen gas (N2) such as those in pharmaceuticals, electronics, mining and food and beverage manufacturing are at high risk due to the gas displacing oxygen.
  • Since nitrogen gas is inert and nontoxic, making up 78% of air, oxygen monitors are often used to detect elevated levels of N2.
  • It can be difficult to detect unsafe levels due to the lack of sensory indicators (smell, taste, color).
  • Oxygen-deficient atmospheres have less than 19.5% oxygen by volume (OSHA). 
  • Oxygen levels must be measured before entering tanks, vessels, or other confined spaces and monitored while occupied by workers.
  • Can accumulate in CSE’s (sewers, basements, workpits, etc.) causing an oxygen enriched environment with higher explosive risk.

O2 Sensor Info

Type: Pumped electrochemical
Range: 0% - 25% volume (0.1% resolution)
Calibration Gas: 18% volume 

Alarm Levels

Depletion Low Alarm: 19.5%
Depletion High Alarm: 18%

Enrichment Low Alarm: 23.5%
Enrichment High Alarm: 25%

Questions about the detection of O2?

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Health Risks and Handling of O2

concentration
symptoms/effects
Over 23%
Risk of oxygen toxicity, flammability, and combustion with other elements is very heightened. The area is not safe without precautions
19.5% - 23%
Generally considered to be safe atmospheric concentrations of O2. 20.9% is the ideal oxygen level in the atmosphere
17% - 19.5%
Officially considered to be an oxygen-deficient atmosphere. No worker should enter an area with this concentration without sufficient protection (supplied-air respirators). Symptoms such as dizziness are possible but not likely
14% - 17%
Dizziness, fatigue, impaired judgement, increased heart rate, reduced attention span and collapse are all likely if working in an area with these concentrations. The area is not safe without protection.
10% - 14%
Lack of oxygen entering the body will prevent proper muscle/motor functions. Nausea and vomiting may occur and may be unable to move out of the area before collapsing. Impaired coordination, judgement and perception. Lips start to turn blue.
8% - 10%
Lips are fully blue. Potential for fainting or falling unconscious. Face becomes ashen and moving becomes very difficult.
6% - 8%
If spending 6 minutes in this concentration, there is a 50% chance of death. If spending 8 minutes in this concentration, there is a 100% chance of death.
4% - 6%
Will likely fall into a coma and may experience convulsions. Breathing will stop leading to death.
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FIRST AID
  • Typically, recovery is fast if the victim is removed from the site of the excess/insufficient oxygen, and given normal levels of oxygen again.
  • Rest is always suggested regardless of the severity of exposure. 
  • In severe cases, sedation, anticonvulsive therapy, and administering additional oxygen should be used. 
  • If a fire/explosion was triggered by excess O2, treat any burns as you normally would. 
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IF ACCIDENTALLY RELEASED
  • Isolate the area with the excess/deficiency of oxygen. 
  • Evacuate all personnel from the area 
  • Shut off oxygen source (if possible, and if the issue is excess O2).
  • Remove all ignition sources (if safe to do so) and ventilate the area. 
  • Notify any safety personnel of the incident, and contact emergency services if the leakage is uncontrollable. 

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