Liquid Nitrogen (LN2)

What Does Liquid Nitrogen (LN2) Mean?

Liquid nitrogen (LN₂) is a cryogenic fluid that is extremely cold, inert, colorless, odorless, nonflammable, and non-corrosive.

Safeopedia Explains Liquid Nitrogen (LN2)

Our atmosphere is composed of 78% nitrogen by volume. Under high pressure, nitrogen becomes liquid nitrogen, a cryogenic liquid with a boiling point of -320.5°F (-195.8°C). Liquid nitrogen has a variety of uses in the medical and pharmaceutical industries. It must, however, be handled according to proper safety procedures since it is both a health hazard and can result in burns or extensive tissue damage.

Applications of Liquid Nitrogen

Liquid nitrogen is used in various industries like aerospace, oil and gas, food and beverage, metal fabrication, and biotechnology.

In the pharmaceutical industry, liquid nitrogen is used to control the temperature in reactor cooling applications and to preserve biological samples.

In the medical industry, liquid nitrogen is used for various purposes, including:

• Preserving blood, bone marrow cells, sperm, ova, and other biological matter
• Preserving bacteria and fungi in laboratory settings
• As part of cryosurgery, such as using a super-chilled scalpel to remove cancer tissue
• In dermatological procedures, to freeze benign growths

Hazards Associated with Liquid Nitrogen

Appropriate safety measures and personal protective equipment (PPE) should be used to ensure maximum safety while handling liquid nitrogen.

Some of the hazards related to cryogenic fluid include the following.

Asphyxiation

When vaporized, liquid nitrogen can expand 695 times in volume and displace oxygen in the atmosphere creating a risk of asphyxiation. When using cryogens indoors, the room should be well ventilated.

Pressure Buildup and Explosion

If cryogenic containers do not have adequate venting or pressure-relief devices, pressure can build upon cryogen evaporation.

Extreme Cold

Liquid nitrogen vapor can quickly freeze skin tissue and eye fluid, and produce effects similar to burns (called cold burns) on the skin. Items that are exposed to liquid nitrogen become extremely cold, and exposed flesh touching it can be torn.

Oxygen Enrichment

When transferring liquid nitrogen, oxygen in the air surrounding a cryogen containment system can dissolve, creating an oxygen-enriched environment as the system returns to ambient temperatures. Since liquid oxygen evaporates slower than nitrogen, it can build up to levels that can cause flammability of surrounding materials like clothing.

Storage and Handling of Liquid Nitrogen

The following measures can be taken for proper storage and handling of liquid nitrogen:

• Store and use liquid nitrogen in well-ventilated areas
• Do not plug, remove, or tamper with pressure relief devices
• Keep cryogenic containers upright during storage, handling, and transport
• Avoid mechanical or thermal shocks to the container
• Do not leave vessel unattended while transferring liquid nitrogen
• Do not fill cylinders and dewars to more than 80% capacity
• Do not touch any uninsulated pipes or equipment containing the cryogenic liquid with unprotected parts of the body
• Store liquid nitrogen in containers with loose-fitting lids
• Use full face shields over safety glasses during transfer and handling