Liquid Nitrogen Safety Requirements

Nitrogen safety is important around liquid nitrogen (LN2). Due to its low temperature, LN2 is extremely dangerous if not handled correctly.

Nitrogen gas is not only extremely safe, but is the most common gas in the earth’s atmosphere. Approximately 78 percent of the air you breathe is nitrogen.

However, because of it's low temperature, liquid nitrogen is dangerous to handle. This is why the Occupational Safety and Health Administration (OSHA) has developed a list of nitrogen safety requirements when working with this gas in its liquid state.

What is liquid nitrogen?

Nitrogen gas is inert, meaning it does not form chemical compounds with other molecules. It is odorless, colorless, and tasteless. This makes it safe to add nitrogen to food or for industrial processes. In addition, Nitrogen, in its liquid form, is easy to transport in tanks or cylinders.

But its most useful property is that liquid nitrogen is cold. Liquid nitrogen has a boiling point of -320°F (-196°C). At any temperature above this is becomes a gas. By piping LN (liquid nitrogen) around or into other gases or objects, it can be used to cool them. This makes it useful as both a coolant and for freezing materials.

What is liquid nitrogen used for?

The ability to freeze or quickly cool water, living tissue or other materials has made LN important in many processes that require extreme cooling or freezing. For example

• Doctors use it for cryosurgery to remove skin lesions or moles.
• It is used for the storage and transportation of blood, body parts, and foods.
• Food producers use it in packaging to remove oxygen and prevent oxidization of the product
• Bottlers use it to remove oxygen from the headspace of bottles before capping.
• Scientists us it for cooling in experiments or to cool CCD cameras for astronomy.
• It is used in industry to temporarily shrink metal parts for precision fitting.
• It is used to freeze scrap rubber and plastic so it can be efficiently ground for recycling.

What are the two main hazards to consider when working with liquid nitrogen?

Although liquid nitrogen is not toxic, it does have two major life threatening hazardous properties. Because liquid nitrogen can evaporate quickly, it can effectively displace air to create an atmosphere that is unable to support life. In addition, it can also cause severe injury due to its intense cold of the liquid.

Hazards when working with liquid nitrogen include:

• Extreme cold
• Asphyxiation
• Oxygen enrichment
• Pressure Buildup
• Explosion

What is the expansion rate of Nitrogen?

Liquid nitrogen expands 696 times in volume when it vaporizes and has no warning properties such as odor or color. Hence, why sufficient liquid nitrogen is vaporized to reduce the oxygen percentage to below 19.5%. Here, there is a risk of oxygen deficiency which may cause unconsciousness.

Understanding the hazards associated with the expansion rate of nitrogen is crucial to prevent accidents and ensure worker safety. The primary hazard related to the expansion rate of nitrogen is associated with rapid pressure changes that can occur when nitrogen is released from a high-pressure vessel or when there is a sudden release of compressed nitrogen gas.

Is liquid nitrogen flammable?

Liquid nitrogen – like nitrogen gas - is not flammable. However, as liquid nitrogen is exposed to normal temperatures and becomes a gas it expands at a rate of 1:694. This has given rise to the idea that LN can cause an explosion. While technically not true, a rapid expansion of the liquid to gas as a result of a leak or a fire surrounding the LN container or transport pipes can create extremely dangerous pressures resulting in an non-flammable explosion of the container.

Is liquid nitrogen dangerous?

There are two primary dangers from liquid nitrogen. The first is asphyxiation. Because of its rapid expansion, it can quickly displace oxygen in an enclosed area. The second is the result of its cold temperatures. It will immediately freeze exposed skin.

Liquid Nitrogen Safety Precautions

1. Do not inhale liquid nitrogen 

Asphyxiation is the primary risk. A person exposed to high levels of nitrogen gas should be removed from the source of the gas and administered rescue breathing if required. Rescuers or people working in enclosed areas with the potential of LN exposure should wear a self-contained breathing apparatus.

2. Wear appropriate personal protective equipment (PPE)

Proper handling. storage, and use of LN is critical to worker safety. Liquid nitrogen can cause burns equivalent to frostbite. Therefore, a positive pressure, full face, air supplied breathing apparatus should be used when working with LN in confined spaces. A face shield that protects the eyes and face should be used to protect from splashes. Insulated gloves, aprons and footwear covering designed for the handling of cryogenic gases should be worn to minimize contact with accidental splashes.

3. Never consume liquid nitrogen directly

Liquid nitrogen as a liquid has a very low boiling point of -196°C and accidental ingestion could cause asphyxiation and airway or gastric perforations due to the extreme cold temperature. You could also take the risk of severely burning your mouth and esophagus.

4. Use liquid nitrogen in well-ventilated areas

You should always ensure you are using liquid nitrogen in well-ventilated areas and never dispose of it by pouring on the floor or pavement. By using liquid nitrogen in a confined or enclosed space you could displace enough oxygen to cause asphyxiation or suffocation. 

5. Only use containers and equipment designed for cryogenic service

By using containers such as dewars, you can ensure that the contents stay in cryogenic state and guarantee safety in operations such as storing or transporting gases.

6. Read and understand the OSHA LN safety guidelines

The occupation Safety Health Administration OSHA Standards number 1910.101, 1910.1200 and 1910.1450 sets the standards for workplace safety for anyone working around LN or other cryogenic gases. Employers or employees should refer to both this OSHA Quick Fact Sheet as well as this published interpretation of the standard for the most current OSHA information.

While there is no standard OSHA signage for LN many safety sign companies offer yellow caution signage with the text "CAUTION - Liquid Nitrogen - Gloves and Face Shield Required".

Liquid Nitrogen Material Safety Data Sheet

Linde, a supplier of liquid gases in the US, has this material data safety sheet available for download (pdf)

Liquid Nitrogen NFPA Rating

The National Fire Protection Association NFPA 704 Rating diamond for liquid nitrogen is

• 0 (no hazard) health
• 0 (will not burn) flammability
• 0 (stable) toxicity
• blank for specific hazards.

Nitrogen Safety Alarms

In the presence of nitrogen we measure the lack of oxygen instead of the specific nitrogen molecules. We choose to measure oxygen for two reasons: the nitrogen molecule is difficult to detect accurately (you'd need a mass spectrometer to be precise), and because our atmosphere is 78% nitrogen any change would be difficult to detect.

The danger of asphyxiation in enclosed areas when liquid nitrogen or any cryogenic gas is stored or utilized can be minimized by installing oxygen depletion safety alarms. The oxygen depletion alarms are designed to measure and alarm before the oxygen concentration in an enclosed space is dangerous to human life.  By installing these devices you can provide employee’s adequate warning before entering an enclosed area where the oxygen level may have dropped below the OSHA standard of 19.5%.

For example the Oxygen Deficiency Alarm for Low Temperatures is designed to protect employees and customers near stored inert gases like cylinders of nitrogen, argon, or helium. It meets all OSHA requirements for safety.

The Oxygen Deficiency Alarm for Low Temperature has the same features, meets all the same OSHA requirements, and is designed to be used in refrigerators or freezers down to -50ºC.

The RAD-0002-ZR utilizes a zirconium dioxide oxygen sensor allowing it to measure oxygen concentrations at extremely low temperatures. The inclusion of this new sensor allows the RAD-0002-ZR to be installed in applications requiring safety monitoring in those extremely low temperatures like food and cryogenic storage.

Portable Nitrogen Safety Devices 

For those working in and out of hazardous environments where liquid nitrogen is stored, used, or produced a portable handheld safety monitor is critical. These devices are designed primarily for enclosed areas where oxygen depletion may cause personal harm. The monitor works by use of audible, visual, and vibrating alarms that indicate to personnel should oxygen levels drop below OSHA compressed gas standards. In addition, the portable device holds up to 72+ hours of charge, ideal for workers "on-the-go".

Compressed Gas Association LN Safety Resources

At CO2Meter, we pride ourselves on providing education and training resources on gas detection and what to do in the event of a potential hazard.

We work alongside many reputable associations like the Compressed Gas Association (CGA). The CGA remains dedicated to providing safety standards and safe practices for the industry and CO2Meter ensures that our devices meet these criteria for our partners across the globe.

Below, you will find a few Liquid Nitrogen CGA code standards:

• CGA P-76, Hazards of Oxygen-Deficient Atmospheres
• CGA SA-29, Safety Alert, Hazards of Liquid Nitrogen in Near-Consumer Applications
• CGA TM-3, eLearning: Safe Handling of Cryogenic Liquids in Portable Containers
• CGA P-12, Safe Handling of Cryogenic Liquids
• CGA P-9, The Inert Gases: Argon, Nitrogen, and Helium

In addition, here are a few additional safety posters in for the "Safe Use of Liquid Nitrogen" and "Liquid Nitrogen in Cryogenic Environments" from the CGA as a free safety resource to share regarding codes, regulations, and industry standards.

For more information on Liquid Nitrogen safety, gas detection safety alarms, or meeting standards you can speak to a CO2Meter specialist at Sales@CO2Meter.com or call us directly at 877-678-4259.