1
Measure of the Director
of the Central European Institute of Technology of Masaryk University
No 1/2022
Safety when working with liquid nitrogen and other
cryogens
(effective as of 9 May 2022)
Pursuant to Article 7(4)(g) of the Rules of Organisation of the Central European Institute
of Technology of Masaryk University and pursuant to the provisions of Sections 101, 102,
103, 108 of Act No. 262/2006 Coll., the Labour Code, as amended (hereinafter the “Labour
Code”); and pursuant to the Chancellor’s Guideline No. 10/2009 on the Organization of
Occupational Safety and Health Protection at MU, I hereby issue the following Measure:
Article 1
Subject Matter
(1) This Measure of the Director of CEITEC MU (hereinafter the “Measure”) is issued to
ensure safe work with liquid nitrogen and other cryogens at all departments of the
Central European Institute of Technology of MU (hereinafter “CEITEC MU”) that work
with these substances.
(2) This Measure articulates the safety guidelines that must be followed by persons
handling liquid nitrogen and other cryogens.
Article 2
Definitions
(1) Cryogenic liquids are substances that are gaseous at normal temperature and
pressure. However, when cooled to a very low temperature they become liquids. Their
boiling point is usually below -150°C. The vapours and gases which escape from these
liquids are very cold. They often condense moist air to form a very dense mist.
Individual cryogens become liquids under different thermal conditions and at different
pressures, but what they all have in common is that they are extremely cold and that
even small amounts of them can produce large volumes of gas. Anyone working with
cryogens must be aware of their hazardous nature and know how to handle them
safely. Each cryogenic liquid has its own specific properties, but most cryogens fall into
one of these groups:
a) Inert gases: inert gases do not chemically react with other substances. They do
not burn or explode. Examples are nitrogen, helium, neon, argon and krypton.
2
b) Flammable gases: some cryogens produce a gas that is flammable in air. The most
common examples are hydrogen, methane, carbon monoxide and liquefied natural
gas.
c) Oxygen: many substances considered non-explosive can burn in the presence of
liquid oxygen. Organic substances can react explosively with oxygen. Thus, the
hazards and precautions for handling liquid oxygen must be followed separate
from other cryogens.
(2) Nitrogen is an inert, non-toxic, non-flammable, chemically little reactive, colourless
and odourless gas that makes up 78% of the Earth’s atmosphere. It is one of the
biogenic elements that constitute the basic building blocks of living matter.
Article 3
Properties of Nitrogen
(1) Properties:
d) odourless,
e) non-flammable,
f) non-toxic,
g) during evaporation, it produces a cold mist that spreads into the surrounding
area,
h) the nitrogen mist falls quickly to the ground.
(2) At ambient temperature (20°C), one litre of liquid nitrogen produces approximately
700 litres of nitrogen gas.
(3) Deeply cooled liquefied gases are hazardous substances because of their physical
properties and because of their physiological effects on the human body. The risk
stems mainly from their low boiling point at normal pressure (-196°C) and low
evaporative heat, which is approximately 10 times lower than that of water.
(4) When the human body comes into direct contact with these liquids, the affected parts
are rapidly cooled to well below freezing. Freezing is painless, but after thawing it is
very painful and leads to shock. Also, deeply hypothermic parts of the equipment can
cause freezing and skin detachment. Even inhaling cold gases alone can cause serious
respiratory damage.
(5) Deeply cooled gases spilled or released freely into the open air evaporate very
intensely due to their low evaporative heat and the resulting fog clouds can be
dangerous, especially in adverse climatic conditions.
Article 4
Cryogenic Liquid Containers
(1) There are several types of cryogenic liquid containers, they are of different sizes and
can store cryogenic liquids for different periods of time. The following points indicate
the most common types of these containers.
3
(2) Dewar’s laboratory transport containers are intended only for short-term storage of
cryogenic liquids, for a few days at most. They consist of a vacuum jacketed cryogenic
container, usually made of silvered glass, with an outer jacket of aluminium or steel.
A loose-fitting stopper-style closure is used to release the vaporized gases so that the
pressure inside does not exceed the atmospheric pressure, while keeping air out to
prevent condensation of liquid oxygen. Generally, these containers are small and easy
to transport. The smallest ones can be carried by means of handles, while larger
models may be fitted with wheels attached to the bottom, or a trolley of appropriate
size may be required. The vacuum space around the cryogen container is equipped
with a pressure valve in case the inner container bursts and cryogen enters the vacuum
space. In this case, pressure could build up inside the vacuum compartment and the
container could burst, so it is safely drained through a safety valve instead.
(3) Before using low-pressure vessels, the outer jacket must be checked for corrosion. The
safety valve must be visually intact. The closure stopper should be easy to close
without jamming.
(4) Large cryogenic liquid storage tanks consist of an inner and an outer vessel with a
vacuum superinsulation between them.
(5) Small vessels (see Figure 2) are designed to hold cryogen for a relatively short period
of time for various laboratory operations. Many of these boxes are equipped with a
foam, loose-fitting or vented lid that can reduce the rate of evaporation of the cryogen
inside the container without increasing the pressure inside the container. Depending
on whether the container is fitted with a lid, the type of lid and the size of the container,
they can hold liquid cryogen for several hours to several days. They are made of
double-layer glass with evacuation between the layers and with a protective aluminium
or steel cover. They are the most fragile of all cryogenic liquid containers, but are
closure
jacket
cryogenic liquid container
Figure 1 - Low pressure Dewar’s vessel
4
unlikely to implode without impact or damage to the glass. When they do shatter,
however, the process is quite vigorous and fragments of glass can be ejected at high
velocity from the top opening.
Figure 2 - Small vessels for cryogens
(6) A polystyrene foam container (with or without lid) can also be used for handling and
short-term storage of liquid nitrogen, see Figure 3.
Figure 3 - Polystyrene foam container for liquid nitrogen handling
(7) Large stainless steel cryogenic liquid containers (Apollo type, etc.), see Figure 4, with
vacuum insulation are used for storage or pumping of larger volumes of liquid nitrogen.
They are usually equipped with wheeled runners with handles, a pumping device,
safety and vacuum valves and a level gauge.
5
Figure 4 - Large containers for cryogenic liquids
(8) During use, no ice should form on the outside of the aluminium cover or on the cap. If
ice forms on the outside of the container, it means that the container may have lost
vacuum and is no longer insulating enough to store cryogenic liquid. If there are cracks
in the inner silvered glass container, liquid cryogen may enter the vacuum space and
when the container is heated, the entire container may explode due to the expanding
cryogen.
(9) If there is any sign of damage or loss of insulation, the vessel must be taken out of
service immediately and tagged to prevent its further use.
Article 4
Guidelines for Handling Cryogenic Liquids
(1) Never touch uninsulated pipes or containers containing cryogenic liquids with any
unprotected part of the body. The tissue damage that could result is the same as
frostbite or burns.
(2) Handle Dewar’s vessels with care. Place them only on a flat surface to prevent them
from tipping over.
(3) Do not use any tools to scrape the inner glass of the containers. Do not use any hard
tools to search the contents inside the containers.
(4) The extremely cold metal will cause the tissue to stick very quickly and tear when
trying to separate.
6
(5) Many substances and materials become brittle on contact with cryogen, and objects
made of them can be more easily broken or otherwise damaged – pieces can fly a
great distance. Avoid using ordinary glass and plastic.
(6) The release of cryogens into the space can cause damage to the floor, electrical cables
and their insulation, pipes, etc.
(7) When overcoming obstacles, the storage vessels may tip over. Handle the containers
with utmost care. Ensure that there are no obstacles on the floor. Observe the
manufacturer’s instructions.
(8) Water from the air can condense and/or freeze in cryogenic liquid storage tanks,
leaving water on the floor where workers can slip. The water must be mopped up
immediately to avoid a slipping hazard.
(9) If water is constantly condensing in the cryogenic liquid container, the operator must
place absorbent materials around the container to prevent the water from becoming a
slipping hazard. If the floor cannot be kept dry, it must be clearly marked “Wet floor,
slipping hazard!” The marking can be obtained from the cleaning service.
Article 5
Storage Conditions
(1) Store and use cryogens only in places with adequate ventilation (prevention of oxygendeficient
atmosphere, below 19.5%).
(2) The site manager is obliged to ensure that cryogens are not stored in confined spaces
(risk of suffocation, explosion).
(3) Cryogenic vessels are equipped with pressure safety valves, which can be used to
control the internal pressure. Under normal conditions, these vessels periodically
release some of the gas. It is forbidden to plug, remove or otherwise replace these
valves as this may lead to an explosion.
(4) Containers should be carried and stored in an upright, bottom-down position.
(5) Small quantities of liquid nitrogen can be stored with care in glass-lined thermoses.
Article 6
Working Conditions and Use of Personal Protective Equipment
(1) Work in a well-ventilated area to avoid an oxygen-deficient atmosphere (less than
19.5%). Although the gases are not poisonous or flammable, suffocation could occur
in enclosed unventilated spaces. Air that lacks sufficient oxygen content causes stupor,
unconsciousness or even death. These gases may not be discernible to the human
senses and may be inhaled as normal air. Ensure that adequate ventilation is provided
when using these gases.
7
(2) When carrying and handling cryogenic liquid containers, it is the operator’s
responsibility to:
a) wear safety shoes, long-sleeved clothing and long but not rolled-up trousers;
b) wear a protective shield or splash-proof goggles;
c) not to wear contact lenses, metal jewellery, watches.
(3) When decanting liquid nitrogen, wear a lab coat and cryogenic apron.
(4) When handling liquid nitrogen or large cooled objects, wear insulating gloves.
(5) Personal protective equipment must be maintained in a usable condition, damaged
equipment must be replaced immediately.
(6) Further information is provided in Annex 1.
Article 7
Authorization of Persons
(1) Only authorized persons with proven knowledge of the operating rules shall have
access to the liquid nitrogen laboratory. Access to the laboratory shall be granted by
the manager, who shall familiarise the staff with the operating rules.
(2) Only authorized persons over 18 years of age, familiar with all safety instructions,
potential hazards and this instruction, may operate liquid nitrogen containers. The
responsibility for familiarisation with the above lies with the site manager.
(3) Repairs, maintenance, and inspections may only be carried out by adequately qualified
persons.
(4) It is prohibited to remove or destroy the labels supplied by the supplier to identify the
contents of the container.
(5) All equipment must be kept in perfect order and cleanliness, which is the responsibility
of the site manager.
Article 8
Hazards Associated with Work with Cryogenic Liquids
(1) When handling liquid nitrogen or helium, any contact with the skin must be avoided
due to the risk of frostbite. Splashing on the skin causes burn-like damage. Eyes are
extremely vulnerable.
(2) When the human body comes into direct contact with cryogens, the affected parts are
rapidly cooled to well below freezing. Freezing is painless, but after thawing is very
painful and leads to shock. Also, deeply hypothermic parts of the equipment (e.g.
outlet valve bodies, unprotected pipes, etc.) can cause freezing and skin tearing. Even
inhalation of cold gases alone can cause serious respiratory damage.
8
(3) Cryogenic liquids and the cold vapours and gases that emanate from them can have
burn-like effects on human skin. Short-term or cursory contact can burn the skin on
the face or hands and can damage delicate tissue, for example around the eyes.
Prolonged skin exposure or contact with cold surfaces can cause frostbite. The skin
then becomes waxy yellow. Initially, the site of contact is painless, but later very
intense stabbing pain is reported in the damaged tissues. Unprotected skin may stick
to the metal cooled by the cryogenic liquid. When trying to separate the body part
from the metal away, the skin may tear and remain on the cold object. Even nonmetallic
materials are dangerous to the touch and sticky at such low temperatures.
Prolonged breathing of very cold air can damage the lungs.
(4) Oxygen is displaced by the escape of helium or nitrogen gas. Oxygen concentrations
in the ambient air below 17% to 18% are not sufficient for human respiration. If a
helium or nitrogen mist escapes into a room, it is recommended to leave the room and
re-enter only when the oxygen content is found to be sufficiently high.
(5) The surface temperature of nitrogen and helium containers can be so low that oxygen
or oxygen-enriched air condenses, contributing to fire hazards. If grease, oil, or other
flammable material is present in the vicinity of the containers, the escape of cryogenic
gases may result in the formation of a potentially flammable liquid due to the
liquefaction of air and oxygen concentration.
(6) Accidental leakage (overflow) – can cause damage to property. This leak is most often
caused by improper handling. Leakage into a laboratory area poses a risk of
suffocation, burns and property damage.
(7) Implosion, the risk can be reduced:
a) Before first use, unpack the container and check for cracks, scratches or chips.
Small cracks or scratches in the glass will spread over time and eventually the glass
will lose its integrity and break.
b) Before each use, check the container for cracks, dents or scratches.
c) Make sure the container is completely dry before filling, as water trapped in tiny
cracks and scratches that subsequently freezes (and expands) can cause breakage.
(8) Careful selection of working materials is necessary. Cold cryogenic liquids can alter the
physical properties of many materials, causing them to become brittle and fail.
(9) Always follow the manufacturer’s instructions.
Article 9
Laboratories with Installed Gas Concentration Sensors
(1) Some of the laboratories have installed sensors detecting oxygen concentration, in
Building E35 these are the following rooms: 241, 1S114, 1S113, 239, 1S124, 1S152,
2S031, in Building E26 it is room 1S05.
(2) Detection of reduced oxygen concentrations in the air of selected laboratories,
including signalling of the condition, activation of safety extraction and blocking of the
use of rooms when the 1st and 2nd level of dangerous concentration is exceeded.
9
(3) When the oxygen concentration decreases, emergency negative pressure ventilation
is triggered.
(4) The laboratory has a traffic light at the door, both outside and inside; the green colour
indicates the optimum amount of oxygen in the laboratory.
(5) If the red light is on, there may be a reduced amount of oxygen, leave the lab
immediately.
(6) A red traffic light is usually accompanied with audible warning signal.
(7) After leaving the laboratory, contact the manager and the central protection desk (ext.
2929) to re-measure the gas concentration and the operations department.
(8) The sensors are calibrated regularly once a year. Calibration is provided by SUKB.
Figure 5 – Oxygen status signalling
Article 10
Instructions for First Aid
(1) Inhalation. In the case of inhalation:
a) Remove or carry the affected person from the infested area to fresh air, bearing
in mind also your own safety.
b) Check to see if the affected person is responding.
c) Tilt the affected person’s head, lift the chin up and check their breathing.
10
d) If the affected person is not breathing normally, initiate CPR.
e) Call 155 and follow the operator’s instructions.
f) If anyone else is on site, ask to bring a defibrillator (AED). The AED is located in
the MRI (Neurosciences) waiting room on the 2nd floor of Building E35.
g) Place your hands over each other on the center of the affected person’s chest.
h) Compress the chest to the depth of 5 to 6 cm at a rate of 100 to 120 compressions
per minute.
i) When using the AED, follow the voice instructions of the device.
j) Upon arrival of the ambulance, continue cardiac massage until paramedics
intervene.
(2) In the case of eye contact
a) In the case of eye contact, rinse thoroughly with plenty of water immediately.
b) Arrange medical assistance if necessary.
(3) In the case of frostbite on contact with the skin
a) When frostbite occurs, rinse the affected area with plenty of water.
b) Cover the wound with a sterile drape. Do not remove clothing.
c) Do not rub the frostbitten parts as this may result in tissue damage.
d) As soon as appropriate, place the affected part in a warm water bath, the
temperature of which does not exceed 40°C.
e) Arrange medical assistance if necessary.
(4) First aid kits are located in each kitchen in buildings E35 and E26, in the other buildings
usually in the corridor behind the partition door.
(5) The injured person is obliged to report each accident to their supervisor and the OSH
Manager. The accident must be recorded in the Accident Information Sheet (located in
each first aid kit). The accident is recorded by the site manager.
(6) The effects of oxygen deficiency can be found in Table 1.
Table 1 - Effects of oxygen deficiency
Volume percentage of
oxygen at sea level
Effects of acute exposure
> 19.5
None, the atmosphere is not oxygen deficient.
< 19.5
Mild effects similar to exposure at elevated altitude.
< 17
Decreased night vision, increased respiratory volume,
increased heart rate, fatigue on exertion.
< 16
Dizziness, accelerated response time, fatigue with mild
exertion.
< 15
Impaired attention, impaired judgment, impaired
coordination, intermittent breathing, rapid fatigue, loss of
muscle control.
< 12
Very poor judgment, very poor muscle coordination, loss of
consciousness, possible permanent damage to the heart or
brain.
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< 10
Inability to move, nausea, vomiting.
< 6 Spasmodic breathing, spasmodic movements, death within 5-
8 minutes.
Article11
Instructions for Handling Containers
(1) Repairs and maintenance of containers can only be carried out when the container has
been depressurised and the contents have been completely evaporated so that the
pressure in the container cannot be restored. Repairs and maintenance may only be
carried out by personnel who are medically and professionally qualified for the job.
(2) When installing hoses and filler pipes, verify that a safety valve is integrated in each
section between the shut-off valves. Liquid gas expands in a confined space when
heated and could cause cracking of pipes and hoses and consequent damage to health
and equipment.
(3) Use a suitable trolley to move the liquid container.
(4) Transporting cryogenic liquids in an elevator poses a potential suffocation hazard.
Transport cryogenic containers without elevator operator. A responsible person in
charge will pick up the container on the delivery floor.
(5) Transport cryogenic liquids slowly and at low pressure to minimize evaporation and
liquid splashing.
(6) Do not place containers on the ground or roll them around their perimeter. Do not
remove or alter fasteners. If the container valve is difficult to handle or the couplings
do not disconnect, contact the supplier. Use only the correct and prescribed couplings.
Do not use adapters.
(7) Use only original Dewar’s closures.
(8) Containers must not be closed tightly! There is a risk of explosion due to pressure!
(9) Store containers only at a well-ventilated place.
(10) Use only spare parts intended for this purpose.
(11) It is always important to read the instructions for use for all containers.
(12) Small quantities of cryogens can be transported between buildings in a suitable lowpressure
Dewar’s container fitted with a lid. Do not carry other items with the
container (e.g. books, drinks, samples, instruments, etc.).
(13) Wear appropriate personal protective equipment.
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(14) Ensure that all process valves are closed during transport.
Article12
Final Provisions
(1) This applies only to workplaces that handle cryogens. Managers of CEITEC MU
departments that handle cryogens are obliged to inform all their subordinate
employees of this measure.
(2) The Head of the Operations Department is responsible for interpreting the individual
provisions of this Measure.
(3) The OSH Manager is responsible for the ongoing updating of this Measure.
(4) The heads of individual workplaces are responsible for monitoring compliance with this
Measure.
(5) This Measure shall become valid on the execution date hereof.
(6) This Measure shall become effective as of 9. 5. 2022.
Annexes: No. 1 - Personal protective equipment for work with liquid nitrogen and other
cryogens
In Brno
Jiří Nantl
Director
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Annex 1: Personal protective equipment for work with liquid nitrogen and other cryogens
Organisation: CEITEC MU, Kamenice 753/5, 625 00 Brno
Workplace:
CEITEC MU, Kamenice 753/5, 625 00 Brno and other CEITEC MU
workplaces
Profession: Specialist (working with cryogens)
Activity Description:
Handling liquid nitrogen and other cryogens.
Work with Dewar’s containers and other cryogen handling equipment.
TYPE OF PPE AND LIKELY DURATION OF USE
Name of PPE More detailed information Note Months
Latex (vinyl, nitrile) gloves Disposable
white jacket
cryogenic gloves
protective shield clear, chemical
protective apron for working with liquid
nitrogen
as required
protective footwear as required
14
Table for the selection of personal protective equipment based on risk assessment
RISKS
Liquid nitrogen and
other cryogens
PHYSICAL
CHEMICAL
(including
nanomaterials)
BIOLOGICAL
INDICATORS
contained in
OTHER
RISKS
mechanical
noise
thermal electric
radiation
(irradi-
ation)
aerosols
fluids
gases,vapours
aerosoles
fluids
materials,
persons,
animals,
etc.
drowning
lackofoxygen
lackofvisibility
fixed liquid
BODY PARTS
AND ORGANS TO BE
PROTECTED
impact
slip
fallfromaheight
vibration
staticcompressionof
abodypart
abrasions,perforations,
cutsandotherwounds,
bitesorstings
interception,pinching
heat,fire
chill
electricshock
staticelectricity
non-ionizing
ionizing
dust,fibres,fumes,
vapours
mists,finemists
immersion
splashing,spraying,
splashingout
solidandliquid
directandindirect
contact
splashing,spraying,
splashingout
directandindirect
contact
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26
head
skull A
whole head B
ears / hearing C
eyes / eyesight D
face E
respiratory organs F
hands G X X X X
arms (parts) H
legs (feet) I
legs (parts) J X X
skin K X X X
torso / abdomen L
body part M
whole body N X X X