Gas Oxygen vs. Liquid Oxygen

What's the Difference?

Gas oxygen and liquid oxygen are both forms of oxygen that are used for various purposes. Gas oxygen is the most common form and is typically stored in high-pressure cylinders. It is easily accessible and can be used for medical purposes, welding, and cutting metals. On the other hand, liquid oxygen is oxygen that has been cooled to a very low temperature, around -183 degrees Celsius, and is stored in insulated containers. It is more dense than gas oxygen and takes up less space, making it suitable for applications where storage space is limited. Liquid oxygen is commonly used in rocket propulsion systems and in medical applications where a higher concentration of oxygen is required.


AttributeGas OxygenLiquid Oxygen
Physical AppearanceColorless and odorlessColorless and odorless
Boiling Point-183°C-183°C
Density1.429 g/L1.141 g/mL
UsesSupports combustion, medical applications, weldingRocket propellant, medical applications, water treatment
StorageStored in high-pressure cylinders or tanksStored in cryogenic containers at extremely low temperatures
ReactivityReacts with flammable materialsReacts violently with combustible materials

Further Detail


Oxygen is an essential element for life on Earth, and it exists in various forms, including gas and liquid. While both gas oxygen and liquid oxygen serve the same purpose of supporting respiration, they differ in several attributes. In this article, we will explore and compare the characteristics of gas oxygen and liquid oxygen, shedding light on their physical properties, storage requirements, transportation methods, and applications.

Physical Properties

Gas oxygen, also known as gaseous oxygen or oxygen gas, is the most common form of oxygen found in the atmosphere. It is a colorless, odorless, and tasteless gas composed of diatomic molecules (O2). Gas oxygen is highly reactive and supports combustion, making it vital for various industrial processes and medical applications.

Liquid oxygen, on the other hand, is oxygen that has been cooled to extremely low temperatures (-183°C or -297°F) to convert it from its gaseous state to a liquid state. In this form, oxygen becomes a pale blue liquid with a density approximately 1.14 times that of water. Liquid oxygen is also highly reactive and can support combustion even more vigorously than gas oxygen due to its increased concentration of oxygen molecules.

Storage Requirements

When it comes to storage, gas oxygen is typically stored in high-pressure cylinders made of steel or aluminum. These cylinders are designed to withstand the high pressure required to keep the gas in its compressed state. The pressure inside the cylinders can range from around 2000 to 3000 pounds per square inch (psi), depending on the specific application.

On the other hand, liquid oxygen requires specialized storage systems due to its extremely low temperature. It is stored in insulated containers known as cryogenic dewars, which are designed to keep the oxygen in its liquid state. These dewars are typically made of stainless steel and have a double-wall construction with a vacuum layer in between to minimize heat transfer and maintain the low temperature of the liquid oxygen.

While gas oxygen cylinders can be easily transported and used in various settings, liquid oxygen storage and transportation require more careful handling due to the need to maintain the low temperature. The cryogenic dewars used for liquid oxygen storage are often bulky and require specialized equipment for transportation.

Transportation Methods

Gas oxygen cylinders are commonly transported in specially designed trucks or vans equipped with secure storage compartments. These vehicles ensure the safe transportation of the cylinders, preventing any damage or leakage during transit. The cylinders are securely fastened to prevent movement and are often accompanied by safety documentation to comply with transportation regulations.

Transporting liquid oxygen, on the other hand, is more complex due to its low temperature and the need to maintain it in its liquid state. Liquid oxygen is typically transported in cryogenic tanker trucks or trailers that are specifically designed to handle and transport cryogenic liquids. These tankers are heavily insulated to minimize heat transfer and equipped with pressure relief systems to ensure safe transportation.

It is worth noting that the transportation of liquid oxygen requires adherence to strict safety protocols and regulations to prevent accidents or incidents that could result from mishandling or improper storage conditions.


Both gas oxygen and liquid oxygen find extensive applications in various industries and medical fields. Gas oxygen is widely used in welding and cutting operations, as it supports the combustion process necessary for these applications. It is also used in the production of steel, chemicals, and glass, as well as in the medical field for respiratory support in hospitals and clinics.

Liquid oxygen, with its higher concentration of oxygen molecules, is often used in more specialized applications. It is commonly employed in rocket propulsion systems, where the high reactivity of liquid oxygen enhances the combustion process, providing the necessary thrust for space exploration. Additionally, liquid oxygen is used in the medical field for portable oxygen concentrators and home oxygen therapy, providing a convenient and efficient source of oxygen for patients with respiratory conditions.

Furthermore, liquid oxygen has found applications in the field of water treatment, where it is used to increase dissolved oxygen levels in water bodies to support aquatic life. It is also utilized in the production of ozone, a powerful oxidizing agent used for disinfection and odor control in various industries.


In conclusion, while both gas oxygen and liquid oxygen serve the same purpose of supporting respiration, they differ in several attributes. Gas oxygen is the most common form found in the atmosphere, stored in high-pressure cylinders, and transported in specially designed vehicles. On the other hand, liquid oxygen requires specialized storage systems, transportation in cryogenic tankers, and finds applications in more specialized fields such as rocket propulsion and medical oxygen therapy. Understanding the characteristics and applications of gas oxygen and liquid oxygen is crucial for ensuring their safe and efficient use in various industries and medical settings.

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