Risk assessment handling liquid nitrogen

Handling liquid nitrogen is considered hazardous.

Hazardous features of liquid nitrogen

Liquid nitrogen is a colourless, odourless and tasteless fluid. The gas is not toxic, nor flammable.

Its boiling point is -196 ºC at atmospheric pressure. Due to its extremely low temperature, liquid nitrogen can cause frostbite upon contact.

When liquid nitrogen evaporates, it expands rapidly into a gas. Because of its low temperature, this gas is denser than oxygen and tends to sink towards the ground. If this gas displaces a significant amount of oxygen in the air, it can lead to oxygen deficiency. This can result in symptoms such as dizziness, unconsciousness, and, in extreme cases, death, which can occur without prior warning.

Risks associated with storage and normal handling, as well as during unforeseen events

General risks

• Moist, unprotected skin can instantly adhere to metal objects that have been cooled by liquid nitrogen. When trying to remove these objects, severe injuries can occur.
• Direct contact of liquid nitrogen with the eyes can result in blindness.
• Liquid nitrogen coming in contact with the skin can lead to frostbite.
• Spilled liquid nitrogen can create a slipping hazard as the soles of shoes might freeze, making them slippery.
• There's a potential for liquid nitrogen leaks into places like sewers, basements, and gutters, where it can accumulate. This can cause pipes to freeze and subsequently burst.
• Working alone without supervision.
• A lack of knowledge among staff members.
• Inadequate training for new employees, students, substitutes, project workers, guests, and other personnel.
• Absence of risk assessments that are documented and tailored to the organization's needs.
• Lack of documented instructions for handling.
• Issues related to inadequate ventilation.

Protective measures

• Always wear protective equipment, including gloves and safety goggles or face shields. To prevent skin contact, wear long trousers, long-sleeved jumpers, and shoes that fully cover the foot.
• If there's potential exposure to large quantities of liquid nitrogen, use protective clothing that doesn't absorb nitrogen.
• Thick-soled boots can help reduce the risk of slipping.
• Ensure that both new and temporary co-workers undergo practical examinations and have access to written handling instructions and information on risk assessments.
• Evaluate the risks of working alone. Implement and communicate safety measures to prevent solitary work.

Tapping of liquid nitrogen

• Liquid nitrogen expands swiftly when it evaporates into gas form. Owing to its low temperature, this gas is denser than oxygen and tends to settle near the ground. As it displaces ambient oxygen, there's a risk of oxygen deficiency, leading to symptoms like dizziness and unconsciousness. In extreme cases, this can result in death without any prior warning.
• Direct contact with liquid nitrogen can cause to frostbite on skin and in eyes.

Protective measures

• Always wear gloves and safety goggles or face shields when handling liquid nitrogen. To prevent skin contact, wear long trousers, long-sleeved jumpers, and shoes that fully cover the foot.
• If there's a potential for exposure to significant amounts of liquid nitrogen, use protective clothing that doesn't absorb nitrogen.
• Thick-soled boots can help reduce the risk of slipping.
• In facilities where nitrogen is dispensed or tapped, an oxygen alarm should be installed if there's a risk of the environment becoming asphyxiating.

Transport of liquid nitrogen

• There's a risk of leakage if the vessel isn't securely sealed or if it tips over.
• Transporting liquid nitrogen in elevators is especially risky because of the confined space. If the elevator malfunctions and the vessel leaks, there's a potential suffocation hazard.
• For vehicles where the cargo area and driver's seat are not separated, transportation of liquid nitrogen is prohibited due to the risks posed by potential leaks.

Protective measures

• Vessels used for transportation must be in good condition and securely fastened to prevent tipping.
• Individuals are not permitted to ride in an elevator alongside these vessels. Affix a sign to the vessel indicating that liquid nitrogen transportation is underway and that elevator use with the vessel is prohibited. If needed, this information should be provided in both Swedish and English.
• Nitrogen should only be transported in vehicles where the driver's compartment is distinct from the cargo area. All relevant ADR regulations must be adhered to.

Storage of liquid nitrogen

• Liquid nitrogen has the potential to cause oxygen deficiency if it leaks. However, as long as there's proper ventilation, the risk of oxygen deficiency remains low.

Protective measures

• Every storage area must be evaluated to ensure adequate ventilation. The air exchange rate in the room or storage area should exceed the potential rate of nitrogen leakage. Ventilation levels in these facilities must not be reduced, even during off-hours like evenings or weekends.
• Consideration should be given to whether a ventilation alarm is necessary.

Handling samples and cryovessels

• There's a risk of equipment explosion due to the pressure increase resulting from nitrogen's transition from liquid to gas. This might happen when storage tubes containing samples are brought to room temperature, especially if liquid nitrogen had previously leaked into them during storage.
• In the event of a significant leak, such as if a vessel is knocked over or dropped, there's a potential for suffocation.
• Direct contact with liquid nitrogen can result in frostbite to both skin and eyes.
• Handling heavy equipment or vessels might lead to physical injuries.

Protective measures

• Always wear gloves, safety goggles, and face shields. For skin protection, wear long trousers, long-sleeved jumpers, and shoes that cover the entire foot.
• If there's a risk of exposure to significant amounts of liquid nitrogen, utilize protective clothing that doesn't absorb the nitrogen.
• Thick-soled boots can help minimize the risk of slipping.
• Depending on the environment, an oxygen alarm might be necessary.
• In the event of a significant leak, evacuate the facilities until it's safe to re-enter. An oxygen meter should be utilized to confirm that oxygen levels are back to normal.
• Heavy lifting can lead to spillage. To mitigate issues associated with heavy lifts, consider using lifting aids or seeking assistance from additional personnel. The design and size of the vessel play a critical role; in some cases, it might be essential to procure more ergonomically designed vessels.

Measures that reduce risks

Only those trained to handle liquid nitrogen and who are familiar with its associated risks and safety measures should be allowed to handle it. Employers must ensure that all staff working with liquid nitrogen are familiar with proper handling procedures.

Recommendations for reducing risks are provided under each specific risk category. In certain unique situations, additional protective measures beyond those outlined might be necessary. Written instructions for handling should always be accessible.

First aid and response in case of spills

Inhalation of high concentrations of nitrogen gas can lead to suffocation, which might occur without any prior signs. One possible symptom is unconsciousness. If someone struggles with breathing, move them to an area with fresh air. Ensure that the affected individual remains warm and immobile. Seek medical advice promptly. Administer CPR if the person stops breathing.

If there's contact with the eyes, rinse them thoroughly with water for at least 15 minutes and seek medical attention.

For frostbite, immerse the affected body part in lukewarm water until sensation and color return to the skin. Refrain from rubbing the frostbitten area, as this can exacerbate the damage. If the frostbite appears deep or extensive, always consult with a medical professional. During transport to the hospital, do not halt the thawing process.

Decontamination

For minor spills, vacate the affected location and assess if further measures are necessary. The necessary response will be influenced by the size of the space, the ongoing activities, and the level of ventilation.

In the event of substantial spills, restrict access to the area. Decontaminate by ensuring adequate ventilation and take steps to prevent the liquid nitrogen from entering drains.

When managing spills, wear protective clothing and use respiratory protection.

Signatures

Risk Assessment Performed by:

Employer's Representative: