EN 60601-2-33:2002/A1:2005

Medical electrical equipment - Part 2-33: Particular requirements for the safety of magnetic resonance equipment for medical diagnosis

Superseded by EN 60601-2-33:2010

Medizinische elektrische Geräte - Teil 2-33: Besondere Festlegungen für die Sicherheit von Magnetresonanzgeräten für die medizinische Diagnostik

Appareils électromédicaux - Partie 2-33: Règles particulières de sécurité relatives aux appareils à résonance magnétique utilisés pour le diagnostic médical

Medicinska električna oprema - 2-33. del: Posebne zahteve za varnost opreme za magnetno resonanco za medicinsko diagnostiko (IEC 60601-2- 33:2002/A1:2005)

General Information

• Status: Withdrawn
• Publication Date: 31-Jan-2006
• Withdrawal Date: 31-Oct-2008
• ICS: 11.040.55 - Diagnostic equipment
• Technical Committee: CLC/TC 62 - Electrical equipment in medical practice
• Drafting Committee: IEC/SC 62B - IEC_SC_62B
• Parallel Committee: IEC/SC 62B - IEC_SC_62B
• Current Stage: 9960 - Withdrawal effective - Withdrawal
• Start Date: 01-Oct-2013
• Completion Date: 01-Oct-2013
• Directive: 93/42/EEC - Council Directive 93/42/EEC of 14 June 1993 concerning medical devices
• Mandate: M/432 - Standardisation Mandate addressed to CEN and CENELEC within the framework of Directive 2007/47/EC amending Directive 90/385/EEC and Directive 93/42/EEC relating to Medical Devices
• Ref Project: SIST EN 60601-2-33:2003/A1:2007 - Medical electrical equipment -- Part 2-33: Particular requirements for the safety of magnetic resonance equipment for medical diagnosis

Relations

• Amends: EN 60601-2-33:2002 - Medical electrical equipment - Part 2-33: Particular requirements for the safety of magnetic resonance equipment for medical diagnosis
• Effective Date: 29-Jan-2023
• Replaced By: EN 60601-2-33:2010 - Medical electrical equipment - Part 2-33: Particular requirements for the basic safety and essential performance of magnetic resonance equipment for medical diagnosis
• Effective Date: 29-Jan-2023

Standards Content (Sample)

SLOVENSKI STANDARD
SIST EN 60601-2-33:2003/A1:2007
01-januar-2007
0HGLFLQVNDHOHNWULþQDRSUHPDGHO3RVHEQH]DKWHYH]DYDUQRVWRSUHPH]D
PDJQHWQRUHVRQDQFR]DPHGLFLQVNRGLDJQRVWLNR,(&$

Medical electrical equipment - Part 2-33: Particular requirements for the safety of

magnetic resonance equipment for medical diagnosis (IEC 60601-2- 33:2002/A1:2005)

Medizinische elektrische Geräte - Teil 2-33: Besondere Festlegungen für die Sicherheit

von Magnetresonanzgeräten für die medizinische Diagnostik (IEC 60601-2-
33:2002/A1:2005)

Appareils électromédicaux - Partie 2-33: Règles particulières de sécurité relatives aux

appareils à résonance magnétique utilisés pour le diagnostic médical (CEI 60601-2-

33:2002/A1:2005)
Ta slovenski standard je istoveten z: EN 60601-2-33:2002/A1:2005
ICS:
11.040.55
SIST EN 60601-2-33:2003/A1:2007 en

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
EUROPEAN STANDARD EN 60601-2-33/A1
NORME EUROPÉENNE
EUROPÄISCHE NORM November 2005
ICS 11.040.55
English version
Medical electrical equipment
Part 2-33: Particular requirements for the safety
of magnetic resonance equipment for medical diagnosis
(IEC 60601-2-33:2002/A1:2005)
Appareils électromédicaux Medizinische elektrische Geräte
Partie 2-33: Règles particulières Teil 2-33: Besondere Festlegungen für die
de sécurité relatives aux appareils Sicherheit von Magnetresonanzgeräten
à résonance magnétique für die medizinische Diagnostik
pour diagnostic médical (IEC 60601-2-33:2002/A1:2005)
(CEI 60601-2-33:2002/A1:2005)

This amendment A1 modifies the European Standard EN 60601-2-33:2002; it was approved by

CENELEC on 2005-11-01. CENELEC members are bound to comply with the CEN/CENELEC Internal

Regulations which stipulate the conditions for giving this amendment the status of a national standard without

any alteration.

Up-to-date lists and bibliographical references concerning such national standards may be obtained on

application to the Central Secretariat or to any CENELEC member.

This amendment exists in three official versions (English, French, German). A version in any other language

made by translation under the responsibility of a CENELEC member into its own language and notified to the

Central Secretariat has the same status as the official versions.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Cyprus, Czech

Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,

Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden,

Switzerland and United Kingdom.
CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
Central Secretariat: rue de Stassart 35, B - 1050 Brussels

© 2005 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.

Ref. No. EN 60601-2-33:2002/A1:2005 E
---------------------- Page: 2 ----------------------
EN 60601-2-33:2002/A1:2005 - 2 -
Foreword

The text of document 62B/573/FDIS, future amendment 1 to IEC 60601-2-33:2002, prepared by

SC 62B, Diagnostic imaging equipment, of IEC TC 62, Electrical equipment in medical practice, was

submitted to the IEC-CENELEC parallel vote and was approved by CENELEC as amendment A1 to

EN 60601-2-33:2002 on 2005-11-01.
The following dates were fixed:
– latest date by which the amendment has to be implemented
at national level by publication of an identical
national standard or by endorsement (dop) 2006-08-01
– latest date by which the national standards conflicting
with the amendment have to be withdrawn (dow) 2008-11-01
__________
Endorsement notice

The text of amendment 1:2005 to the International Standard IEC 60601-2-33:2002 was approved by

CENELEC as an amendment to the European Standard without any modification.
__________
---------------------- Page: 3 ----------------------
NORME CEI
INTERNATIONALE
IEC
60601-2-33
INTERNATIONAL
2002
STANDARD
AMENDEMENT 1
AMENDMENT 1
2005-08
Amendement 1
Appareils électromédicaux –
Partie 2-33:
Règles particulières de sécurité relatives aux
appareils à résonance magnétique utilisés
pour le diagnostic médical
Amendment 1
Medical electrical equipment –
Part 2-33:
Particular requirements for the safety
of magnetic resonance equipment
for medical diagnosis
 IEC 2006 Droits de reproduction réservés  Copyright - all rights reserved

International Electrotechnical Commission, 3, rue de Varembé, PO Box 131, CH-1211 Geneva 20, Switzerland

Telephone: [phone] Telefax: [phone] E-mail: [e-mail] Web: www.iec.ch

CODE PRIX
Commission Electrotechnique Internationale
PRICE CODE
International Electrotechnical Commission
МеждународнаяЭлектротехническаяКомиссия
Pour prix, voir catalogue en vigueur
For price, see current catalogue
---------------------- Page: 4 ----------------------
60601-2-33 Amend. 1  IEC:2006 – 3 –
FOREWORD

This amendment has been prepared by subcommittee 62B: Diagnostic imaging equipment, of

IEC technical committee 62: Electrical equipment in medical practice.
This bilingual version (2006-02) replaces the English version.
The text of this amendment is based on the following documents:
FDIS Report on voting
62B/573/FDIS 62B/586/RVD

Full information on the voting for the approval of this amendment can be found in the report

on voting indicated in the above table.
The French version of this amendment has not been voted upon.

The committee has decided that the contents of this amendment and the base publication will

remain unchanged until the maintenance result date indicated on the IEC web site under

"http://webstore.iec.ch" in the data related to the specific publication. At this date, the

publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
___________
Page 13
6.8.2 INSTRUCTIONS FOR USE
Replace, on page 18, the existing item pp) by the following:
pp) Recommended training

INSTRUCTIONS FOR USE shall recommend that training is needed for physicians and the

OPERATOR to operate the MR EQUIPMENT safely and effectively. This training shall include

emergency procedures, including those for the issues described in this subclause under

− cc) Emergency medical procedures
− ee) CONTROLLED ACCESS AREA
− mm) EMERGENCY FIELD SHUT DOWN UNIT
− nn) Fire precautions
− ss) Emergency actions in the event of a QUENCH.
Add, on page 18, the following new item ss):
* ss) Emergency actions in case of a QUENCH

The INSTRUCTIONS FOR USE shall include instructions on how to identify a QUENCH and how

to act in the event of a QUENCH, especially when the venting system of the
superconducting magnet system fails.
---------------------- Page: 5 ----------------------
60601-2-33 Amend. 1  IEC:2006 – 5 –
Page 19
6.8.3 Technical description
Replace, on page 20, the existing item cc) by the following:
* cc) Safety provisions in the event of a quench
For MR EQUIPMENT equipped with superconducting magnets, the ACCOMPANYING
DOCUMENTS shall

– state the requirements for a venting system for the superconducting magnet which

connects the cryostat of the magnet to the outside atmosphere and which is designed

to withstand a QUENCH and to protect nearby persons in the event of a QUENCH;

– provide guidelines for the construction (dimensions, position, assembly and material to

be applied) of the venting system for the superconducting magnet inside and outside

the examination room;

– recommend a preventive maintenance program, which states that regular checks of the

adequateness of the function of the venting system for the superconducting magnet

are to be made;

– state requirements for the design of the examination room to increase safety of the

patient and other persons inside and outside the examination room in the event of

failure of the venting system during a quench. The suggested design shall address the

issues of reducing pressure build-up, temperature decrease and oxygen depletion

during a quench. A number of acceptable solutions for such provisions, demonstrated

to be effective by simulation or test, shall be listed, so that even when the venting

system of the superconducting magnet fails to work adequately, the chance of a

hazard for the PATIENT or other persons inside as well as outside the examination

room, as caused by PRESSURE build-up, temperatures decrease or oxygen depletion
during the QUENCH, is reduced considerably;

– state the need for the USER to establish an emergency plan for a quench, including a

situation in which the venting system for the superconducting magnet fails to function

adequately;

– state the need for possible extra control measures for the PATIENT ventilation system in

order not to expose the PATIENT to additional helium transported to the PATIENT via the

PATIENT ventilation system. The PATIENT ventilation system should have its inlet

opening in a safe place (such as at a low level in the examination room or directly

connected to the air-conditioning of the examination room), or be connected to a

QUENCH detector, so that the PATIENT ventilation system can be automatically controlled

when a QUENCH occurs and will not transport helium to the PATIENT inside the scanner.

NOTE 1 The venting system for the superconducting magnet is considered to be the cryogenic vent pipe and all

the extra components necessary to safely accommodate a QUENCH.

NOTE 2 Examination room configurations demonstrated by simulation or test that are acceptable include:

− configurations in which the RF door opens outwards or is a sliding RF door;

− configurations in which the RF door opens inwards, if these include extra precautions to prevent PRESSURE

build up. This can be realized by one of the following

• an extra examination room ventilator system, which can be switched on (possibly automatically via an

oxygen monitor in the ceiling of the examination room to detect the escape of helium gas) in the

event of a QUENCH; or

• an opening in the wall or ceiling of the examination room, venting towards an open area; or

---------------------- Page: 6 ----------------------
60601-2-33 Amend. 1  IEC:2006 – 7 –

• a possibility of opening the observation window in the examination room outward or by sliding; or

• a second independent venting system for the superconducting magnet that remains operational in

case the regular venting system for the superconducting magnet is obstructed; or
• equivalent methods demonstrated to be effective by simulation or test.
Page 45
Annex BB – Guidance and rationale for particular subclauses
Add, on page 57, a rationale for subclause item 6.8.2 ss) as follows:
Concerning 6.8.2 ss)

In addition to the information given in item cc) of 6.8.2 on emergency medical procedures and

item ff) of 6.8.2 on liquid and gaseous cryogens, this item provides information pertinent to

emergencies present in the event that magnet helium gas escapes from the magnet into the

examination room or other adjacent rooms during a QUENCH. This situation may be present

when the venting system of the superconducting magnet fails either in part or fully during a

magnet QUENCH. In this case, hazards may be present for the personnel involved. The

information provided here will be useful for the OPERATOR in establishing an emergency plan

adapted to local requirements.

While a QUENCH as such is a rare event, the additional failure of a venting system of the

magnet is even more unlikely. Although thousands of MR SYSTEMS are in operation, there

have been only a few reports to date regarding accidents or near accidents involving personal

injuries in relationship to a QUENCH. Nevertheless, the MANUFACTURERS are required to point

out the potential hazard of the combined event and to provide information pertinent to this

type of emergency. Note that the information covers the highly unlikely, yet possibly serious

event of a malfunctioning venting system at the time of a quench of the superconducting

magnet.
What is a QUENCH?

During a QUENCH, the magnet loses its super-conductivity. The magnetic field ramps down in a

matter of seconds – typically lasting approximately 20 seconds. The magnet begins to warm

up. Liquid helium boils off at a rate of 500 to 1 500 l within a few minutes and expands

quickly. The exact boil-off rate amount depends on the fill level as well as the field strength of

the magnet. A 3 T magnet may have a higher boil-off rate than a 1,5 T magnet. One litre of

liquid helium translates into approximately 700 l of gaseous helium. During maximum

conditions this means approximately 1 000 m of gas. A manual QUENCH may be initiated by

activating the Emergency field shut down unit. Another source for quenching is when the

helium fill level decreases to a point where the magnet begins to warm up. In rare instances,

a spontaneous QUENCH may be observed that cannot be explained by the presence of obvious

causes.

Hissing or whistling noises caused by the quickly escaping stream of cold helium gas may

accompany a QUENCH. Plumes of white fog sink to the floor mainly from the upper part of the

magnet from the vicinity of the QUENCH line due to condensation of both water vapour and air.

The stream of helium gas diminishes in a matter of minutes. Air near the non-insulated

components of the magnet and the QUENCH line condenses into liquid air and drips to the

floor.
---------------------- Page: 7 ----------------------
60601-2-33 Amend. 1  IEC:2006 – 9 –
Risks associated with a failing venting system

The purpose of the venting system of the superconducting magnet is to securely exhaust

gaseous helium to the outside. The main element of this system is a conduit that is designed

to transport the escaping helium gas to a safe open area. The possibility of a QUENCH should

be taken into careful consideration during the design of both the magnet and the venting

system of the superconducting magnet. As a result, a QUENCH should be completely harmless

to personnel. Also, neither the magnet nor the MR installations as such should be subject

...

62B/522/CDV
COMMITTEE DRAFT FOR VOTE (CDV)
PROJET DE COMITÉ POUR VOTE (CDV)
Project number IEC 60601-2-33 Ed.2 A1
Numéro de projet
IEC/TC or SC: Date of circulation Closing date for voting (Voting
62B
Date de diffusion mandatory for P-members)
CEI/CE ou SC:
Date de clôture du vote (Vote
2004-04-09
obligatoire pour les membres (P))
2004-09-10

Titre du CE/SC: Appareils électromédicaux - TC/SC Title: Medical electrical equipment -

Diagnostic imaging equipment
Secretary: Hartmut Duschka
Secrétaire:
Also of interest to the following committees Supersedes document
Intéresse également les comités suivants Remplace le document
62B/521/MCR
Functions concerned
Fonctions concernées
Safety EMC Environment Quality assurance
Sécurité
CEM Environnement Assurance qualité

CE DOCUMENT EST TOUJOURS À L'ÉTUDE ET SUSCEPTIBLE DE THIS DOCUMENT IS STILL UNDER STUDY AND SUBJECT TO CHANGE. IT

MODIFICATION. IL NE PEUT SERVIR DE RÉFÉRENCE. SHOULD NOT BE USED FOR REFERENCE PURPOSES.

LES RÉCIPIENDAIRES DU PRÉSENT DOCUMENT SONT INVITÉS À RECIPIENTS OF THIS DOCUMENT ARE INVITED TO SUBMIT, WITH THEIR

PRÉSENTER, AVEC LEURS OBSERVATIONS, LA NOTIFICATION DES COMMENTS, NOTIFICATION OF ANY RELEVANT PATENT RIGHTS OF

DROITS DE PROPRIÉTÉ DONT ILS AURAIENT ÉVENTUELLEMENT WHICH THEY ARE AWARE AND TO PROVIDE SUPPORTING

CONNAISSANCE ET À FOURNIR UNE DOCUMENTATION EXPLICATIVE. DOCUMENTATION.
Titre : Title : IEC 60601-2-33 Ed. 2 Am.1: Particular
requirements for the safety of magnetic
resonance equipment for medical diagnosis
Note d'introduction Introductory note
IEC 60601-2-33 Ed. 2.0 was published in May 2002. This
edition was expected to remain unchanged until June
2005. However, an amendment is required to provide for
the users of the standard a technically more in-depth text
for the safety requirement of MR equipment in case of a
quench (see the rationale for an early amendment of IEC
60601-2-33 Ed. 2.0 given in Annex A).
The amendment is planned to be published by October
2004 as asked in SMB/2610/QP, 2003-08.
ATTENTION ATTENTION
CDV soumis en parallèle au vote (CEI) Parallel IEC CDV/CENELEC Enquiry
et à l’enquête (CENELEC)

Copyright © 2004 International Electrotechnical Commission, IEC. All rights reserved. It is

permitted to download this electronic file, to make a copy and to print out the content for the sole

purpose of preparing National Committee positions. You may not copy or "mirror" the file or

printed version of the document, or any part of it, for any other purpose without permission in

writing from IEC.
FORM CDV (IEC)
2002-08-09
---------------------- Page: 1 ----------------------
IEC 60601-2-33 Ed. 2 Am. 1 - 2 - 62B/522/CDV
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
MEDICAL ELECTRICAL EQUIPMENT –
Part 2-33 Ed.2 Amendment 1:
Particular requirements for the safety
of magnetic resonance equipment for medical diagnosis
FOREWORD

This amendment to International Standard IEC 60601-2-33 Ed.2 has been prepared by

subcommittee 62B: Diagnostic imaging equipment, of IEC technical committee 62: Electrical

equipment in medical practice.
The text of this standard is based on the following documents:
FDIS Report on voting

Full information on the voting for the approval of this standard can be found in the report on

voting indicated in the above table.

This publication has been drafted in accordance with the ISO/IEC Directives, Part 3.

In this Particular Standard, the following print types are used:

– requirements, compliance with which can be tested, and definitions: in roman type

– notes, explanations, advice, introductions, general statements, exceptions, and references: in smaller type

– test specifications: in italic type

– TERMS USED THROUGHOUT THIS PARTICULAR STANDARD THAT HAVE BEEN DEFINED IN CLAUSE 2

AND IEC 60601-1: IN SMALL CAPITALS.

The committee has decided that the contents of this publication may remain unchanged until

December 2006. At or before this date, the publication will be
• reconfirmed;
• withdrawn;
• replaced by a revised edition, or
• amended.
A bilingual version of this standard may be issued at a later date.
---------------------- Page: 2 ----------------------
IEC 60601-2-33 Ed. 2 Am. 1 – 3 – 62B/522/CDV

The numbering of sections, clauses, and subclauses of this Amendment corresponds to that

of the Particular Standard. The changes to the text of the Particular Standard are specified by

the use of the following words:
“Replace in the Particular Standard”: means that the clause or subclause of the
Particular Standard is replaced completely by the text of this Amendment.

“Add to the Particular Standard”: means that the text of this Amendment is additional to

the requirements of the Particular Standard.

“Change the Particular Standard”: means that the clause or subclause of the Particular

Standard is changed as indicated by the text of this Amendment.
6.8.2 INSTRUCTIONS FOR USE
Replace in the Particular Standard Clause 6.8.2 pp) by:
pp) Recommended training

INSTRUCTIONS FOR USE shall recommend that training is needed for physicians and the

OPERATOR to operate the MR EQUIPMENT safely and effectively. This training shall

include emergency procedures, including those for the issues described in this clause

under
cc) Emergency medical procedures
ee) CONTROLLED ACCESS AREA
mm) EMERGENCY FIELD SHUT DOWN UNIT
nn) Fire precautions
ss) Emergency actions in case of a QUENCH.
Add to the Particular Standard in clause 6.8.2 ss)
ss) Emergency actions in case of a QUENCH

The INSTRUCTIONS FOR USE shall include instructions how to identify a QUENCH and how

to act in case of a QUENCH, especially when the venting system of the superconducting

magnet system fails.
Replace in the Particular Standard Clause 6.8.3 cc) by:
6.8.3 Technical Description
cc) Provisions to control safety in case of a quench
For MR EQUIPMENT equipped with superconducting magnets, the ACCOMPANYING
DOCUMENTS shall

- state the requirements for a venting system for the superconducting magnet which

connects the cryostat of the magnet to the outside atmosphere and which is
designed to withstand a QUENCH and to protect nearby persons in the case of a
QUENCH.
- provide guidelines for the construction (dimensions, position, assembly and
material to be applied) of the venting system for the superconducting magnet
inside and outside the examination room
---------------------- Page: 3 ----------------------
IEC 60601-2-33 Ed. 2 Am. 1 – 4 – 62/522/CDV
- recommend a preventive maintenance program, which state that regular checks of
the adequateness of the function of the venting system for the superconducting
magnet are to be made.

- state requirements for the design of the examination room to increase safety in

case of failure of the venting system during a quench. A number of acceptable

solutions for such provisions, demonstrated to be effective by simulation or test,

shall be listed, so that even when the venting system of the superconducting

magnet fails to work adequately, the chance for a hazard for the PATIENT or other

persons inside as well as outside the examination room, as caused by PRESSURE
build-up, temperatures decrease or oxygen depletion during the QUENCH is reduced
considerably.

- state the need for the USER to establish a safety emergency plan for the case of a

QUENCH, including the situation whereby the venting system for the
superconducting magnet fails to function adequately

- state the need for possible extra control measures for a PATIENT ventilation system

in order not to expose the PATIENT to additional helium transported to the PATIENT

via the PATIENT ventilation system. The PATIENT ventilation system should have its

inlet opening at a safe place (such as at low level in the examination room or

directly connected to the air-condition of the examination room), or is connected to

a QUENCH detector so that the PATIENT ventilation system can be automatically
controlled when a QUENCH occurs and will not transport helium to the PATIENT
inside the scanner.

Note 1: The venting system for the superconducting magnet is considered to be the cryogenic vent pipe and all the

extra components necessary to safely accommodate a QUENCH.

Note 2: Fore the examination room configuration solutions demonstrated by simulation or test that are acceptable

include:
- Configurations in which the RF door opens outwards

- Configurations where the RF door opens inwards, if these include extra precautions to prevent PRESSURE build

up. This can be realized by

- an extra examination room ventilator system, which can be switched on in case of a QUENCH,

- or a PRESSURE-equalizing opening in the wall or ceiling of the examination room, venting towards an

open area,

- or a possibility to open outwards or slide by the observation window in the examination room as a

PRESSURE equalizing means,

- or a second independent venting system for the superconducting magnet that remains operational in

case the regular venting system for the superconducting magnet is obstructed,
- or equivalent methods demonstrated to be effective by simulation or test.
Add to the particular standard in Annex BB clause 6.8.2 ss)
Concerning 6.8.2 ss)

In addition to the information given in Clause 6.8.2 cc) on emergency medical procedures and

clause 6.8.2 ff) on liquid and gaseous cryogens, this clause provides information pertinent to

emergencies present in the event that magnet helium gas escapes from the magnet into the

examination room or other adjacent rooms during a QUENCH. This situation may be present

when the venting system of the superconducting magnet fails either in part or fully during a

magnet QUENCH. In this case, hazards may be present for the personnel involved. The

information provided here will be useful for the OPERATOR in establishing an emergency plan

adapted to local requirements.

While a QUENCH as such is a rare event, the additional failure of a venting system of the

magnet is even more unlikely. Although thousands of MR SYSTEMS are in operation, there are

only a few reports to date regarding accidents or near accidents that involve personal injuries

in relationship to a QUENCH. Nevertheless, the MANUFACTURERS are required to point out the

potential hazard of the combined event and to provide information pertinent to this type of

---------------------- Page: 4 ----------------------
IEC 60601-2-33 Ed. 2 Am. 1 – 5 – 62B/522/CDV

emergency. Note that the information covers the highly unlikely, yet possibly serious event of

a malfunctioning venting system at the time of a quench of the superconducting magnet.

What is a QUENCH?

During a QUENCH, the magnet loses its super-conductivity. The magnetic field ramps down in a

matter of seconds - typically lasting approximately 20 seconds. The magnet begins to warm

up. Liquid helium boils off at a rate of 500 to 1500 litres within a few minutes and expands

quickly. The exact boil-off rate amount depends on the fill level as well as the field strength of

the magnet. A 3T magnet may have a higher boil-off rate than a 1.5 T magnet. One litre of

liquid helium translates into approximately 700 litres of gaseous helium. During maximum

conditions this means approximately 1000 m³ gas. A QUENCH may be released by pressing the

magnet’s "emergency shut-down" switch. Another source for quenching is a helium fill level

that decreases to a point where the magnet begins to warm up. In rare instances, a

spontaneous QUENCH may be observed that cannot be explained by the presence of obvious

causes.

Hissing or whistling noises caused by the quickly escaping stream of cold helium gas may

accompany a QUENCH. Plumes of white fog sink to the floor mainly from the upper part of the

magnet from the vicinity of the QUENCH line due to condensation of both water vapour and air.

The stream of helium gas diminishes in a matter of minutes. Air near the non-insulated

components of the magnet and the QUENCH line condenses into liquid air and drips to the

floor.
Risks associated with a failing venting system

The purpose of the venting system of the superconducting magnet is to securely exhaust

gaseous helium to the outside. The main element of this system is a conduit that is designed

to transport the escaping helium gas to a safe open area. The possibility of a QUENCH should

be taken into careful consideration during the design of both the magnet and the venting

system of the superconducting magnet. As a result, a QUENCH should be completely harmless

to personnel. Also, neither the magnet nor the MR installations as such should be subject to

damage during a QUENCH.

However, when upon a quench the venting system fails, an emergency situation arises.

Helium is lighter than air, non-poisonous and non-flammable. However, since it displaces

oxygen, the risk of suffocation exists. Cryogenic helium escaping into the ambient air leads to

white clouds caused by condensation. These clouds will adversely affect visibility.

Persons may be rendered unconscious by the amount of helium entering their respiratory

system. Depending on the helium concentration present in the air, a few breaths may suffice

to result in unconsciousness.

In addition, escaping helium is extremely cold, possibly causing hypothermia and frostbite.

The latter results in injuries resembling burns (cryogenic burns) after the skin is exposed to

normal temperature levels. Skin contact with cold parts or liquid air may also lead to

...