Topping up cell storage vessels with Liquid Nitrogen

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MRC Cl
inical Sciences Centre

Imperial College Faculty of Medicine

Hammersmith Campus

Du Cane Road

London W12 0NN



Risk Assessment Form for Laboratory Procedure






1

MRC Clinical Sciences Centre

Version 3 JULY 09




RISK ASSESSMENT FOR A LABORATORY PROCEDURE


Technique Title



Topping up cell storage vessels with Liquid Nitrogen.


Staff involved



All Staff involved with transporting LN2 and filling cell storage vessels


Hazards involved



Chemicals:
Liquid Nitrogen a
nd Nitrogen gas



Cryogenic burns and frostbite



Asphyxiation



Hypothermia



Manual handling



Pressurised vessel


Route of exposure



Skin, eyes, inhalation of aerosols and gas, contact.


Harm



Chemicals:
The respective COSHH forms for the above substances must
be read prior to
this technique commencing so that their hazards and control measures are understood.



Cryogenic burns
:
LN
2
(
-
196°C) and items stored in it can burn unprotected skin and
cause frostbite from continued exposure



Asphyxiation
:
An O
2

depleted en
vironment can result from LN
2

evaporation to gaseous N
2

(expansion rate 1:683) in enclosed and poorly ventillated areas
.



Hypothermia:

Staff can develop this from continued exposure to cold environment.



Manual Handling:
Manual handling injuries from tra
nsporting Pressurized LN2 containers
around the campus, filling up cell storage banks etc.



Pressurised Vessel:

Injuries resulting from inappropriate storage, movement and use of
pressurised vessels.


Identify any persons and any special risks associated w
ith the technique and steps that
must be taken to minimise them.



Person carrying out the work:
There is a high risk of asphyxiation, especially in confined
or enclosed areas if the gas is released unexpectedly. This is why work is always carried
out in pa
irs, just in case the person doing the filling becomes overcome by the fumes.
There is a real danger of cryogenic burns from the liquid itself or the hose it is being
decanted from. Bystanders are at risk as well from splashes. Continued exposure without
p
roper insulated clothing, gloves could easily lead to frostbite. Continued working in very
cold environments could lead to Hypothermia.



Other Persons:
Risk of inhalation of the gas. Risk of inhalation to estates staff and nearby
office workers if they are
very close to the venting point of the gas. Risk of splashes of
cryogenic liquids on exposed skin, eyes etc. to passers
-
by




Controls 1:

Training and experience to carry out the task properly, and to deal with
emergencies quickly. Personal protective equipm
ent: fastened lab coat,
absorbent insulated
gloves must always be worn when handling anything that is or has been in recent contact
with liquid nitrogen. Cryogenic gloves are designed to be used in the vapour phase only

MRC Cl
inical Sciences Centre

Imperial College Faculty of Medicine

Hammersmith Campus

Du Cane Road

London W12 0NN



Risk Assessment Form for Laboratory Procedure






2

MRC Clinical Sciences Centre

Version 3 JULY 09



Identify any persons and any special risks associated w
ith the technique and steps that
must be taken to minimise them.

and
should not be immersed into liqu
id nitrogen under any circumstances
. They
should be a loose fit to facilitate easy removal. Gauntlet style gloves are not recommended
as liquid can drip into them and become trapped against the skin
-

sleeves should cover
the ends of gloves or alternativel
y, a ribbed cuff style may be worn. A full face visor should
be used to protect the eyes and face where splashing or spraying may occur and, in
particular, where operations are carried out at eye level. A laboratory coat or overalls
should be worn at all t
imes. Non
-
absorbent cryogenic aprons are also commercially
available.

Open pockets and turn
-
ups where liquid could collect should be avoided. Trouser
bottoms should overlap boots or shoes for the same reason. Sturdy shoes with a re
-
enforced toecap are reco
mmended for handling liquid nitrogen vessels. Open toed shoes
should not be worn under any circumstances. When not in use, all PPE should be stored in
an appropriate manner (e.g. visors on wall mounted hooks) to ensure that it does not
become damaged or co
ntaminated. A personal Low oxygen alarm needs to be worn as well
while decanting the liquid.



Controls 2:
Pressurized vessels are checked for safety by trained Engineers annually and
given a certificate if they comply with standards. All equipment used to t
ransport or store
the material needs to be well maintained.


Emergency Spillage Procedure



Evacuate the area. Deploy warning signs if necessary.



Ventilate the area. Open doors and windows or activate forced ventilation to allow any spilt
liquid to evapora
te and the resultant gas to disperse.



Try to stop the release if at all possible e.g. turn off valves, but only if it is safe to do so
-

always wear protective clothing.



Do not re
-
enter area without self contained breathing apparatus unless it is proved sa
fe to
do so. The presence of oxygen deficiency monitors will indicate the oxygen levels in the
vicinity. Breathing apparatus should only be used by trained personnel.



Prevent liquid nitrogen from entering drains, basements, pits or any confined space where

accumulation may be dangerous.



All accidents must be reported to the Lab Manager / Safety Supervisor or the
departmental first aid personnel, and CSC Safety via an accident report form:

http://safety.csc.mrc.ac.uk/CSCAccidentReportForm.pdf


First aid mea
sures



Where inhalation has occurred, the victim (who may be unconscious) should be removed to
a well ventilated area.
Rescuers should not put themselves at risk
-

a contaminated
area should not be entered unless considered safe. Breathing apparatus may be

required but should only be used by trained personnel.
The person should be kept
warm and rested whilst medical attention is obtained. If breathing has stopped then
resuscitation should be commenced by a trained first aider.




Where contact has occurred,
the aim should be to slowly raise the temperature of the
affected area back to normal. For minor injuries, clothing should be loosened and the
person made comfortable. Clothing should not be pulled away from burned or frozen skin.
The affected area should
be doused with copious quantities of tepid water (40
o
C) for at
least 15 minutes and a sterile burn dressing applied to protect the injury until the person
can be taken to receive hospital treatment.
Do not:



use a direct source of heat such as a radiator



p
ermit smoking or alcohol consumption



give analgesics (e.g. paracetamol, aspirin)



MRC Cl
inical Sciences Centre

Imperial College Faculty of Medicine

Hammersmith Campus

Du Cane Road

London W12 0NN



Risk Assessment Form for Laboratory Procedure






3

MRC Clinical Sciences Centre

Version 3 JULY 09



First aid mea
sures

For major injuries apply first aid as far as is practicable and arrange for the victim to receive
medical attention. On arrival at hospital, medical staff should be provided
with a copy of BOC
Gases Guidance Note G4968
‘Treatment by medical practitioner or hospital’
.


Waste Disposal



The safest way to dispose of this is to take all vessels to a well ventilated area, preferably
outside and allow to evaporate. Permission must b
e sought from the Lab manager before
carrying this out. The Estates department need to be informed also in case of any
emergencies and also so that they can inform all personnel that might come into contact
with the liquid/gas.


Include a brief stepwise d
escription of the technique



Working in pairs and wearing the above mentioned PPE, one person carries out appropriate
checks on the pressurised liquid nitrogen vessel and if necessary venting pressure to
between 10
-
15psi prior to filling the cell storage v
essels. The other person observes, in
case they are overcome by the gas or an accident occurs



The operator should ensure that the flow of liquid has ceased and the lid(s) should be
replaced on the cell storage vessel(s).



Once completed, all PPE must be st
ored someplace suitable where it won’t get damaged.



Storage of Pressurized vessels and cell storage vessels in labs requires an additional
assessment of the risks to personnel from the venting of the vessel, or gas evaporation in
an enclosed space. The bel
ow information can be found on Spectrum to help make an
assessment of the risk.



1: venting of a pressurized vessel in a room:



The resulting O2 concentration in the room will be: %O
2

= 100 x
Vo












Vr

Where, for nitrogen:


Vo = 0.2095
(Vr
-

Vg)

Vr = room volume (m
3
)

Vg = maximum gas release, which is the liquid volume capacity of the


Vessel V x gas expansion factor.


Vr =

155

Vg =

61.47

Vo =

0.2095(155


61.47)

= 19.59


%O2 in the room if the 100 L vessel vents is

reduced to = 12.63%.

This level is low enough to physical and intellectual performance to diminish without awareness of
it. It would be better that this vessel was stored outside the building. If it is to be kept in the room
a low O
2

alarm should be insta
lled outside the door to warn people about the risk.



2: Oxygen reduction in the room due to evaporation from 1 cell storage vessel in
4S2


This can be calculated using the following formula:


C =
L







Vn



approximately



MRC Cl
inical Sciences Centre

Imperial College Faculty of Medicine

Hammersmith Campus

Du Cane Road

London W12 0NN



Risk Assessment Form for Laboratory Procedure






4

MRC Clinical Sciences Centre

Version 3 JULY 09



Include a brief stepwise d
escription of the technique

Where: C =

gas concentration


the gas expansion factor for Liquid N
2

is 683



L = gas release (m
3

/ h)



V = room volume (m
3
)



n = air changes per hour


There is 1 81 L refrigeration unit in this room.


This refrigeration unit’s evaporation rate is 0.76 L per

24 hours
(Manufacturer’s data).


Due consideration should be made in this assessment for women of child
-
bearing years,
and a full re
-
assessment should be carried out upon notification of pregnancy.


This assessment has been carried out by the person resp
onsible for the work.
A copy of
this assessment has been sent to CSC Safety.



RESPONSIBLE PERSON

NAME

SIGNATURE

DATE

Person carrying out the
assessment




Principal Investigator




Group Safety Supervisor




Annual Review