Why Monitor Oxygen Deficiency?

Pressurized gas cylinders and dewars that store cryogenically liquefied gases are used in countless applications in manufacturing, production, and research. A leak from any of these containers can quickly displace the oxygen in the surrounding vicinity and move levels below dangerous thresholds. This can put personnel at the risk of oxygen depletion or, even worse, asphyxiation.

Any company, laboratory, or university involved in the handling and storage of these containers need to actively monitor the oxygen levels in those areas as a safety precaution. Moreover, the U.S. and other Western countries have regulatory agencies that create and enforce requirements for a safe workplace.

Primary Method to Measure O2 Deficiency

Oxygen Deficiency Monitor in Work Environment
Model 221R Oxygen Deficiency Monitor installed in area with several gas cylinders

The Oxygen Deficiency Monitor, also known as the Oxygen Deficiency Analyzer, serves as the ideal solution for this application. The unit will generally feature audible alarms and adjustable setpoints to alert people to exit the area when the oxygen suddenly drops below predetermined levels. There are many monitors available on the market, and competing manufacturers differentiate their offering through performance, various programming and ease-of-use features.

Most Oxygen Deficiency Monitors utilize sensor-based measurement technology with the electrochemical sensor and zirconium-oxide sensor being the most popular. However, there are key performance differences that separate these two competing approaches. The next section will discuss this information in more detail.

Electrochemical Sensor vs Zirconium Oxide Sensor

electrochemical sensor and zirconium oxide sensor
Electrochemical sensor (left) and zirconium oxide sensor (right). A zirconium-oxide sensor has more reading stability when monitoring ambient air

Because accuracy is the main metric for performance, the Analyzer needs to resist drifting when measuring ambient air of any room. In fact, if the unit drifts too far, it can inadvertently trigger a false alarm and cause an unnecessary rush to exit the area. Temperature and pressure fluctuations are often behind incidents of drifting. Some common examples include a sudden weather pattern change and even the cycling operation of an air conditioning system as it turns on and off.

Testing has shown that a zirconium-oxide sensor provides better stability. This is observed in settings, involving both temperature and pressure fluctuations. On the other hand, an electrochemical sensor performs poorly when introduced to the same variables due to its inherent sensitivities.

OSHA Guidelines

OSHA image
OSHA set guidelines for workplace safety in the U.S.

Companies operating in the U.S. must comply with guidelines published by OSHA. The information below summarizes what OSHA has established for acceptable oxygen levels in the workplace and when those levels become dangerous:

  • Normal air contains about 20.9% oxygen
  • Any atmosphere with the oxygen level equal to or less than 19.5% by volume is deemed oxygen-deficient and immediately dangerous to life or health
  • Any atmosphere with the oxygen level equal to or more than 23.5% by volume is deemed oxygen-rich

More information can be found on OSHA’s website:


Frequently Asked Questions

What type of monitor will detect oxygen-deficient atmospheres?

An oxygen deficiency or oxygen depletion monitor is used to detect an oxygen-deficient atmosphere in a room or confined space where people may be present. AMI’s Model 221R Oxygen Deficiency Monitor uses a zirconium oxide oxygen sensor to detect changes in oxygen levels in the atmosphere and will sound an alarm if the oxygen level falls below 19.5%.

How is oxygen deficiency measured?

Oxygen deficiency in the atmosphere of a room or confined space is measured by an oxygen deficiency monitor. The oxygen deficiency monitor uses a zirconium oxide sensor to detect the oxygen level in the air. If the oxygen level fall below the typical atmospheric level of 20.9%, the oxygen deficiency monitor will sound an alarm and activate relays that can be used to operate ventilation fans or other safety devices.

What is an oxygen depletion sensor?

An oxygen depletion sensor is a gas analyzer, used to monitor the oxygen concentration in the surrounding atmosphere. It works as a safety device within a room or confined spaces to alert personnel if the oxygen level falls below 20.9%.

What is oxygen-deficient?

Oxygen deficiency is a serious condition that can occur when the atmosphere a person is breathing air in falls below the typical 20.9% oxygen level found in the atmosphere. An oxygen-deficient atmosphere is anything less that 19.5% oxygen as defined by OSHA. AMI’s Model 221R Oxygen Deficiency Monitors will detect an oxygen-deficient environment and alarm personnel of the condition.

What are three effects of oxygen deficiency?

Oxygen deficiency can have serious effects on the human body that can eventually lead to death. If oxygen levels drop from the typical 20.9% to 19%, a person may feel dizzy, and their coordination may be affected. At 16% oxygen, the individual may have an increased pulse rate, rapid breathing, and compromised judgement. Below 10%, the individual can experience loss of consciousness or death.

Which is one of the first signs of oxygen deficiency?

The first signs of oxygen deficiency include a decreased ability to work strenuously and impaired coordination. This can occur when the oxygen level in the atmosphere of a confined space falls from the typical 20.9% to a level within the range of 15-19%. AMI’s Model 221R Oxygen Deficiency Monitor will sound an alarm to alert personnel if the oxygen level in a space falls to 19.5%.

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