Cryogenic liquid cylinders that are pressurized vessels are sometimes incorrectly referred to as dewars. Cryogenic liquid cylinders are insulated, vacuum-jacketed pressure vessels. They come equipped with safety relief valves and rupture discs to protect the cylinders from pressure buildup.
These containers operate at pressures up to psig and have capacities between 80 and liters of liquid. Tanks may be spherical or cylindrical in shape. They are mounted in fixed locations as stationary vessels. Tanks are designed to ASME specifications for the pressures and temperatures involved. Do not store liquid nitrogen in any container with a tight fitting lid; a loose fitting lid helps preventing air and moisture from entering the container and at the same time allows pressure to escape.
Liquid or low-temperature gas from any of the specified cryogenic substances will produce effects on the skin similar to a burn. The extremely low temperature of the liquid can cause severe frostbite or eye damage upon contact.
Symptoms of frostbite include change in skin color to white or grayish yellow and the pain after contact with liquid nitrogen may quickly subside. Items in contact with liquid nitrogen become extremely cold.
Touching these items may result in torn flesh. Liquid nitrogen gas released in a confined space can displace sufficient oxygen to make the atmosphere incapable of sustaining life and cause asphyxiation without warning. Degrees of asphyxia will occur when the oxygen content of the working environment is less than Heat flux into the cryogen from the environment will vaporize the liquid and potentially cause pressure buildup in cryogenic containment vessels and transfer lines.
On vaporization liquid nitrogen expands by a factor of ; one liter of liquid nitrogen becomes Adequate pressure relief must be provided to all parts of a system to permit this routine out gassing and prevent explosion. Cryogenic fluids with a boiling point below that of liquid oxygen are able to condense oxygen from the atmosphere. Repeated replenishment of the system can thereby cause oxygen to accumulate as an unwanted contaminant. Similar oxygen enrichment may occur where condensed air accumulates on the exterior of cryogenic piping.
Violent reactions, e. Because of the large expansion ratio of liquid to gas , it is important to provide adequate ventilation in areas using liquid nitrogen. A minimum of six air changes per hour is required in these areas.
Oxygen level monitoring should be provided for areas where oxygen displacement may occur. OSHA has established Remember, nitrogen has no warning properties! Store and use liquid nitrogen containers with adequate ventilation.
Do not store containers in confined areas or in areas unprotected from the extremes of weather unless the container is permanent and designed for outside storage. Cryogenic containers are equipped with pressure relief devices designed to control the internal pressure. Under normal condition these containers will periodically vent product. Do not plug, remove or tamper with any pressure relief device. Cryogenic containers must be stored, handled, and transported in the upright position.
Use tongs to withdraw objects immersed in a cryogenic liquid - Boiling and splashing always occur when charging or filling a warm container with cryogenic liquid or when inserting objects into these liquids. Do not transport liquid nitrogen in wide-mouthed glass Dewars or Dewars not protected with safety tape. Use only approved containers. Impact resistant containers that can withstand the extremely low temperatures should be used.
Materials such as carbon steel, plastic and rubber become brittle at these temperatures. Only store liquid nitrogen in containers with loose fitting lids Never seal liquid nitrogen in a container.
A tightly sealed container will build up pressure as the liquid boils and may explode after a short time. Never touch non-insulated vessels containing cryogenic liquids. Flesh will stick to extremely cold materials. Even nonmetallic materials are dangerous to touch at low temperatures. Never tamper or modify safety devices such as cylinder valve or regulator of the tank Liquid nitrogen should only be stored in well-ventilated areas do not store in a confined space.
Do not store liquid nitrogen for long periods in an uncovered container. Skip to Content. Urgent Care. In This Section. Dermatology Looking for services or physicians who can help treat this condition?
Click Here. What to Do Keep the area clean and dry. Skin contact. Skin contact with LN can result in burns, blistering, and severe frostbite injury, which can occur within seconds of exposure. Skin damage from exposure to LN may be extensive enough to require surgery or amputation.
Personal protective equipment such as safety goggles, face shields, insulated gloves loosely fitting , and lab coats or aprons can reduce the risk of skin injury. LN has been used to instantly freeze drinks and food and to produce a spooky vapor effect. When applied to food that is served in a manner that ensures complete evaporation of LN as well as a normal food temperature, it is generally considered a safe and fun way to enjoy these unique creations.
However, LN added to food or drink at the point of sale and immediately before ingestion has resulted in cases of serious injury. According to the Food and Drug Administration , products such as "Dragon's Breath," "Heaven's Breath," and "Nitro Puff" that are often sold in malls, food courts, and kiosks are prepared by adding LN to food or drink immediately before it's to be consumed.
Unless allowed to completely evaporate, the LN can remain so cold that it could causes burns or frostbite injuries.
Even if the LN fully evaporates, these injuries may still occur due to the exceptionally cold food temperatures that can result from contact with LN. Another dangerous effect with ingestion of LN is due to its large expansion ratio 1 to The expansion ratio is the volume of a certain amount of a substance in liquid form compared to the volume of the same amount in gas form at room temperature.
If swallowed, the rapid expansion of evaporating LN in the stomach can result in major stomach injuries such as perforations and ruptures. Inhaling cold vapors released by LN can trigger breathing problems, especially among people with baseline respiratory illnesses like asthma.
This includes vapors coming from LN-treated food or drink. Even more concerning is that LN is an asphyxiant, meaning it displaces oxygen in the air. If inhalation occurs, especially in an enclosed space without proper ventilation, oxygen concentrations can become dangerously low and lead to dizziness, unconsciousness, and even death.
Never allow liquid nitrogen to make contact with any part of your body.
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