Compliance Training

Liquid Nitrogen Safety

Liquid Nitrogen Safety THIS TRAINING SESSION IS

RECOMMENDED FOR:

Liquid nitrogen is a colorless, odorless, extremely cold liquid and gas under pressure. Nitrogen Employees who use liquid ni-
trogen or dispense it for use by
can displace oxygen in the work area, leading to asphyxiation. One volume of liquid nitrogen others.
will expand to produce 696.5 equivalent volume of gas. Although nitrogen is considered non-
toxic and non-flammable, nitrogen in liquid form poses a variety of hazards. Liquid nitrogen
must be handled and stored properly to avoid injury to the user and others in the work area.
Training Objectives
Health Effects This training module will provide
participants with an understand-
ing of the following for liquid
Inhalation of nitrogen in excessive amounts can cause dizziness, nausea, vomiting, excess nitrogen:
salivation, loss of consciousness, and death. In such cases of massive over-exposure, death may
·· Properties;
result from errors in judgment, confusion, or loss of consciousness that prevents self-rescue.
·· Health effects of exposure;
At low oxygen concentrations, unconsciousness and death may occur in seconds and without
·· Handling requirements;
warning.
·· Personal protective equipment
and other safety precautions;
Skin contact with liquid nitrogen can cause tissue freezing due to the low temperature of the ·· Storage and dispensing instruc-
cryogenic liquid, resulting in severe burns. Eye contact with liquid nitrogen and its vapors can tions; and
result in tissue freezing and severe cryogenic burns. ·· Spill control and disposal.

Container Use and Storage

Cryogenic liquid cylinders are insulated, vacuum-jacketed pressure vessels. They come
Interactive Training
equipped with safety relief valves and rupture discs to protect the cylinders from pressure build
Reminder
up. Product may be withdrawn as a gas by passing liquid through an internal vaporizer or as a
Compliance Training is an inter-
liquid under its own vapor pressure.
active training program in which
you can address questions with
Liquid nitrogen should be stored in a cool, dry, well-ventilated, low fire-risk area. Protect other staff members or supervi-
sors to obtain clarification for
containers against physical damage and extremes of temperature. Liquid nitrogen storage areas
situations in your work setting.
should be kept clean and free from flammable materials. Make sure that containers are prop-
erly vented to prevent build-up of pressure. Write down any questions that
you have about the training
topic and address them with your
Pressure Relief Valves Safety Training Coordinator or
supervisor.
Cryogenic containers are equipped with pressure relief devices to control internal pressure.
Under normal conditions, these containers will periodically vent product. This venting will
be audible as a slight hissing sound. Do not plug, remove, or core.” This lid is a mechanical cover for the opening and an
tamper with any pressure relief device. insulating cover for the top of the dewar, but allows venting of
vapors to prevent pressure buildup.
Ice or frost buildup on a pressure relief valve can be removed
with a damp cloth. Wear proper personal protective equip- Liquid nitrogen is to be dispensed only into smaller Dewars
ment (PPE) when removing frost. Discontinue use and con- which either (a) have carrying handles or (b) are on wheels
tact the vendor if you experience any difficulty operating the or (c) are 500 mL or smaller, and which have pressure relief
container valve or its connections. Use the proper connection. valves or pressure venting lids. A wide-base Dewar, which is
DO NOT USE ADAPTERS! stable on a wheeled cart, qualifies as “on wheels.” Persons fill-
ing must be in constant attendance of the filling operation.
Piping
If the receiving vessel is small enough, place it on an adjust-
Use piping and equipment designed to withstand the pres- able table, so that the delivery is immediately at the mouth
sures to be encountered. On gas withdrawal systems, use a of the receiving vessel (i.e., do not allow the liquid nitrogen
check valve or other protective apparatus in any line or piping to fall through a distance to reach the receiving vessel). If the
from the container to prevent reverse flow. vessel is too large for the table, other provisions must be made
for safely raising the vessel up to the delivery tube.
To prevent cryogenic liquids or cold gas from being trapped
in piping between valves, the piping should be equipped with Do not hold the vessel with unprotected hands while filling.
pressure relief devices. Only transfer lines designed for use
with cryogenic liquids should be used. Do NOT move/bend the copper fill tube. It causes wear that
will eventually cause the tube to break.
Some elastomers and metals such as carbon steel may become
brittle at low temperatures and will easily fracture. These Wear appropriate personal protective equipment as described
materials must be avoided in cryogenic service. It is recom- in the PPE section below.
mended that all vents be piped to the exterior of the building
or to a well-ventilated indoor space. Handling Precautions

Moving Containers ·· Treat liquid nitrogen, and any object cooled with liquid
nitrogen with caution.
·· Use a suitable hand truck for container movement.
·· Do not allow liquid nitrogen to be trapped in clothing
·· Containers should be handled and stored in an upright next to skin.
position.
·· Use only approved unsealed containers. Never pour into
·· Do not drop, tip, or roll containers on their sides. a coffee thermos. Never seal it in any container, as it will
explode.
·· Do not remove or interchange connections.
·· Never dip a hollow tube into liquid nitrogen, as it may
Dewar Bottles spurt liquid.

·· Use in a well-ventilated area. Do not store in a confined

Small quantities of liquid nitrogen can be stored in Dewar
space.
bottles. Dewar bottles are hollow-walled containers, which
provide excellent insulation. Dewar bottles will keep liquid ·· Do not dispose of liquid nitrogen by pouring it on the
nitrogen for a fairly long period of time. floor, as it could displace enough oxygen to cause suf-
focation.
These vessels utilize a lid, sometimes also called a “neck tube
Compliance Training {Liquid Nitrogen Safety}
·· Do not store for long periods in an uncovered container, Spill Clean-Up and Disposal
because oxygen can condense from the air into the liquid
nitrogen. If the air over the nitrogen circulates, this liquid When liquid nitrogen is spilled, it can release a rapidly vapor-
oxygen can build up to levels that may cause violent izing cloud that could create an oxygen-deficient atmosphere.
reactions with organic materials (even materials that are In the case of a spill/leak, you should evacuate while the
ordinarily nonflammable). For example, a severe clothing spilled liquid is allowed to evaporate. Ventilation to the spill
fire could result from ignition in the presence of liquid area should be increased, if possible, and the oxygen level
nitrogen. monitored before re-entry is allowed. Personnel that must re-
enter the area (either for rescue or clean-up operations) must
·· Do not allow any unprotected part of the body to come
wear a self-contained breathing apparatus. Insulating gloves,
into contact with uninsulated pipes or equipment that
safety goggles and protective clothing should be worn as nec-
contains cryogenic product. The extremely cold metal
essary to prevent any skin or eye contact with liquid nitrogen.
will cause the flesh to stick fast and tear when attempting
to withdraw from it.
To dispose of liquid nitrogen, return the container and any
unused product to the supplier. Do not attempt to dispose
Personal Protective Equipment
of unused product. Do not attempt to reclaim the product.
Check with your supervisor or safety coordinator regarding
Recommended personal protective equipment for handling
liquid nitrogen disposal procedures specific to your practice.
liquid nitrogen includes:

·· A full face shield over safety glasses;

·· Loose-fitting thermal insulated or leather gloves. Gloves

should be loose fitting so they can be quickly removed if
cryogenic liquid is spilled on/in them. Insulated gloves
are not made to permit the hands to be submerged into
a cryogenic liquid. They will only provide short term
protection from accidental contact with the liquid.

·· Long sleeve shirts, and trousers without cuffs (do NOT

tuck pants into shoes or boots);

·· Safety shoes are recommended for people involved in the

handling of containers; and,

·· In emergency situations, self-contained breathing ap-

paratus (SCBA) may be required.

·· Persons filling Dewars must wear full-length non-cuffed

trousers (covering tops of shoes) or a full-length apron,
and shoes that will not admit spilled cryogen, and which
are easy to remove quickly. In addition, goggles and cryo-
gloves should be worn.

Compliance Training {Liquid Nitrogen Safety} y 2009

 Compliance Training Test
Liquid Nitrogen Safety

NAME: DATE:

SIGNATURE: STAFF POSITION:

There are 10 questions to the test for Liquid Nitrogen Safety. There is no pass or fail grade to the test. Review the training information to find the correct
answers to any questions that may have been missed.

1 A regular thermos (such as used for coffee) may be used 7 Liquid nitrogen should not be disposed of by pouring it
to store small amounts of liquid nitrogen. on the floor, as it could displace enough oxygen to cause
suffocation.
Select One T F
Select One T F
2 Liquid nitrogen should be stored in a cool, dry, well-
ventilated, low fire-risk area. 8 Persons filling Dewars must wear full-length non-cuffed
trousers (covering tops of shoes) or a full-length apron,
Select One T F
and shoes that will not admit spilled cryogen, and which
are easy to remove quickly. In addition, goggles and cryo-
3 When liquid nitrogen is spilled, it can release a rapidly
gloves should be worn.
vaporizing cloud that could create an oxygen-deficient
atmosphere. Select One T F

Select One T F
9 When working with liquid nitrogen, pants should be
tucked into boots to help prevent skin exposure.
4 Under normal conditions, cryogenic containers do NOT
periodically vent product. Select One T F

Select One T F
10 Do not allow any unprotected part of the body to come
into contact with uninsulated pipes or equipment that
5 Inhalation of nitrogen in excessive amounts can cause
contains cryogenic product, because the extremely cold
dizziness, nausea, vomiting, excess salivation, loss of
metal will cause the flesh to stick fast and tear when at-
consciousness, and death.
tempting to withdraw from it.

Select One T F
Select One T F

6 Regular exam gloves may be worn when working with
liquid nitrogen.

Select One T F