EN ISO 12894:2001

SLOVENSKI STANDARD
01-februar-2003
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Ergonomics of the thermal environment - Medical supervision of individuals exposed to
extreme hot or cold environments (ISO 12894:2001)
Ergonomie des Umgebungsklimas - Medizinische Überwachung von Personen, die einer
extrem heißen oder kalten Umgebung ausgesetzt sind (ISO 12894:2001)
Ergonomie des ambiances thermiques - Surveillance médicale des personnes exposées
a la chaleur ou au froid extremes (ISO 12894:2001)
Ta slovenski standard je istoveten z: EN ISO 12894:2001
ICS:
13.100 Varnost pri delu. Industrijska Occupational safety.
higiena Industrial hygiene
13.180 Ergonomija Ergonomics
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN ISO 12894
NORME EUROPÉENNE
EUROPÄISCHE NORM
June 2001
ICS 13.100; 13.180
English version
Ergonomics of the thermal environment - Medical supervision of
individuals exposed to extreme hot or cold environments (ISO
12894:2001)
Ergonomie des ambiances thermiques - Surveillance Ergonomie des Umgebungsklimas - Medizinische
médicale des personnes exposées à la chaleur ou au froid Überwachung von Personen, die einer extrem heißen oder
extrêmes (ISO 12894:2001) kalten Umgebung ausgesetzt sind (ISO 12894:2001)
This European Standard was approved by CEN on 15 June 2001.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard 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 Management Centre or to any CEN member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CEN member into its own language and notified to the Management Centre has the same status as the official
versions.
CEN members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece,
Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36  B-1050 Brussels
© 2001 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 12894:2001 E
worldwide for CEN national Members.

CORRECTED 2001-11-07
Foreword
The text of the International Standard from Technical Committee ISO/TC 159 "Ergonomics" of
the International Organization for Standardization (ISO) has been taken over as an European
Standard by Technical Committee CEN/TC 122 "Ergonomics", the secretariat of which is held
by DIN.
This European Standard shall be given the status of a national standard, either by publication
of an identical text or by endorsement, at the latest by December 2001, and conflicting
national standards shall be withdrawn at the latest by December 2001.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of
the following countries are bound to implement this European Standard: Austria, Belgium,
Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy,
Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and the United
Kingdom.
Endorsement notice
The text of the International Standard ISO 12894:2001 was approved by CEN as a European
Standard without any modification.
INTERNATIONAL ISO
STANDARD 12894
First edition
2001-06-15
Ergonomics of the thermal environment —
Medical supervision of individuals exposed
to extreme hot or cold environments
Ergonomie des ambiances thermiques — Surveillance médicale des
personnes exposées à la chaleur ou au froid extrêmes
Reference number
ISO 12894:2001(E)
©
ISO 2001
ISO 12894:2001(E)
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ii © ISO 2001 – All rights reserved

ISO 12894:2001(E)
Contents Page
Foreword.iv
Introduction.v
1 Scope .1
2 Normative references .1
3 Terms and definitions .2
4 Principles of medical supervision of individuals .2
4.1 General.2
4.2 Ergonomic investigations.3
4.3 Occupational exposure .5
Annex A (informative) General principles underlying ergonomic investigations in which volunteer
subjects may experience discomfort .6
Annex B (informative) Medical effects of exposure to hot and cold.9
Annex C (informative) Medical supervision of individuals exposed to extreme hot environments in the
laboratory .13
Annex D (informative) Medical supervision of individuals exposed to cold environments in the
laboratory .18
Annex E (informative) Practical requirements of medical supervision in the laboratory, or during field
studies with volunteers not normally exposed .23
Annex F (informative) Occupational exposures to extreme heat and cold.25
Bibliography.29
ISO 12894:2001(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO
member bodies). The work of preparing International Standards is normally carried out through ISO technical
committees. Each member body interested in a subject for which a technical committee has been established has
the right to be represented on that committee. International organizations, governmental and non-governmental, in
liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical
Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 3.
Draft International Standards adopted by the technical committees are circulated to the member bodies for voting.
Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this International Standard may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights.
International Standard ISO 12894 was prepared by Technical Committee ISO/TC 159, Ergomomics, Subcommittee
SC 5, Ergonomics of the physical environment.
Annexes A to F of this International Standard are for information only.
iv © ISO 2001 – All rights reserved

ISO 12894:2001(E)
Introduction
This International Standard is one of a group of standards which specify methods for measuring and evaluating hot,
moderate and cold thermal environments. International Standards or Technical Reports, which describe the
evaluation of hot and cold thermal environments, give advice on the acceptability of these environments for human
exposure, taking account of the activity level and the effects of clothing worn. That advice is given on the basis that
the individuals concerned are healthy, that is, without any medical factor which might predispose them to ill effects
from the thermal environment. Furthermore, biological variability prevents the accurate prediction of the response
of any particular individual to climatic extremes. For these reasons, it is necessary to provide appropriate medical
supervision for individuals who are to be exposed to extreme thermal environments. This International Standard
describes a method to determine the degree of medical supervision relevant to different types of exposure, in order
to limit the risk of any individual suffering from ill health.
INTERNATIONAL STANDARD ISO 12894:2001(E)
Ergonomics of the thermal environment — Medical supervision of
individuals exposed to extreme hot or cold environments
1 Scope
This International Standard provides advice to those concerned with the safety of human exposures to extreme hot
or cold thermal environments. Extreme thermal environments are those which result in a high rate of heat gain or
loss by the body. A precise definition of such environments cannot easily be given, as the change in body heat
storage depends on clothing and activity as well as the parameters of the climatic environment. As a guide, the
boundaries of extreme environments might be considered to be as follows: for hot environments, a wet bulb globe
temperature of 25 °C; for cold environments an air temperature of 0 °C or below.
Extreme environments can only be tolerated for limited periods of time before a risk of ill health results. Control
measures are necessary to ensure the safety of those so exposed, one of which is the provision of appropriate
medical supervision prior to and during exposures.
This International Standard is intended to assist those with responsibility for such exposures to reach decisions
about the appropriate level of medical supervision in different situations. This International Standard should be read
and used in the context of other relevant guidance and legislation.
This guidance is applicable to laboratory and occupational exposures to extreme environments. In either case an
assessment should be made of the expected thermal stress on the individual, but the detailed arrangements for
medical supervision will differ. Control of occupational exposures must also satisfy national health and safety
legislation.
The laboratory or climatic chamber studies for which this International Standard will be relevant include those in
which people may be exposed to high or low ambient conditions or local heating or cooling. Studies may, for
example, investigate physiological or psychophysical responses to the environment or the benefit of clothing or
other protective equipment. Scientific investigations and demonstrations for teaching purposes are included in the
scope. In some countries, such studies are subject to specific legislation and, in all cases, experimental exposures
should be conducted in the context of accepted ethical criteria as detailed in relevant national and international
statements (see informative annex A and the bibliography).
Extremes of environment may be only one component of the total physiological stress imposed in a study. In such
cases, appropriate advice must also be obtained with regard to any medical supervision required prior to exposure
to the other stressors involved, for example whole body vibration.
In some cases, ergonomic investigations are conducted in the field, for example, to document the physiological
stress of particular occupations. If the overall stress of the task is increased as a result of the proposed study, this
International Standard will be relevant.
This International Standard does not apply to the use of hypo or hyper thermia in the course of medical
investigation or treatment.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of
this International Standard. For dated references, subsequent amendments to, or revisions of, any of these
publications do not apply. However, parties to agreements based on this International Standard are encouraged to
ISO 12894:2001(E)
investigate the possibility of applying the most recent editions of the normative documents indicated below. For
undated references, the latest edition of the normative document referred to applies. Members of ISO and IEC
maintain registers of currently valid International Standards.
ISO 9886, Evaluation of thermal strain by physiological measurements.
ISO 13731, Ergonomics of the thermal environment — Vocabulary and symbols.
3 Terms and definitions
For the purposes of this International Standard, the following terms and definitions apply.
3.1
independent medical officer
qualified medical practitioner identified in a study protocol as responsible for the arrangements for medical fitness
assessment and health monitoring in support of a study to which this International Standard applies and who is not
the principal investigator
3.2
experimenter
the member of the investigation team who is in overall control of a particular experimental session
3.3
medical fitness assessment
procedure by which the state of past and present health of an individual is reviewed to identify any possible medical
predisposition to harm from exposure to extreme thermal environments
3.4
health monitoring
process in which the acute effects on the individual resulting from exposure to an extreme thermal environment are
observed and interpreted by someone with appropriate training, utilizing physiological monitoring and clinical
observation
NOTE The purpose is to detect any indications that an individual may no longer be adequately tolerating the exposure
conditions, and therefore to prevent any serious ill health arising, if necessary by removal of the individual from the exposure.
3.5
occupational physician
qualified medical practitioner who has received appropriate training and who is responsible for the supervision of
the health at work of employees in one or more enterprise
3.6
principal investigator
where more than one person is responsible for the design of a study a principal investigator should be nominated
and he or she will normally be responsible for obtaining ethical approval for a study and for ensuring that adequate
arrangements are made for medical supervision of the experimental subjects
NOTE In the case of multicentre studies with a centrally agreed protocol, the person organizing the study, i.e. the promoter,
may be responsible for seeking ethical approval.
4 Principles of medical supervision of individuals
4.1 General
The use of the relevant International Standards, given in clause 2, for the assessment of the thermal environment,
will allow exposures to be controlled in such a way that the risk of illness arising is minimized. Where body core
temperature is maintained in the band 36,0 °Cto 38,0 °C then serious general health effects, resulting from
2 © ISO 2001 – All rights reserved

ISO 12894:2001(E)
changes in body heat storage, are unlikely, although not entirely unknown. Core temperature is defined in
ISO 13731 and described in ISO 9886. In this International Standard, where reference is made to values of core
temperature, it is intended that these will have been obtained from valid measurement sites, such as those
described in ISO 9886.
If core temperature departs from the range previously specified, there is a progressively increasing risk of acute ill
health, specifically heat stroke (heat hyperpyrexia) or profound hypothermia, either of which can be life threatening.
Disorders resulting from changes in body heat storage are not, however, the only types of ill health that can arise in
extreme thermal environments. For example, in the cold, asthmatic attacks may occur, (particularly in association
with exercise), angina may be precipitated, and rhinitis, coughs and nose bleeds have all been reported. Also
peripheral cooling can result in frostbite. In the heat, blood flow redistribution can result in episodes of low blood
pressure and the risk of collapse before significant heat gain has occurred.
The main illnesses which can arise from changes in body heat storage in hot or cold environments are summarized
in informative annex B. This also gives information on the other health effects which can occur in hot and cold
conditions.
ISO 9886 and ISO 13731 apply only to healthy subjects in whom the normal physiological control of body
temperature is unimpaired. Also, they are unable to take account of the variability of responses between different
individuals, although some large differences, such as those between acclimatized and unaclimatized individuals,
are considered. For these reasons, it will be important, in the circumstances described below, to include a system
of medical supervision of the exposed individuals in risk management. Such supervision may entail both medical
fitness assessment prior to exposure and health monitoring during exposure.
4.2 Ergonomic investigations
4.2.1 Introduction
Ergonomic investigations may be conducted in the laboratory or in the field. In either case, the protection of the
individuals participating in the studies must be a major consideration.
4.2.2 Laboratory studies
4.2.2.1 General
Studies should be conducted according to accepted ethical guidelines, for example, as contained in the “Helsinki
Declaration” (see [8] in the bibliography). The study protocol should be approved by a local research ethics
committee. The Principal Investigator and each Experimenter should be aware of their duties towards the subjects
both in the design and conduct of the investigations. They should ensure that only individuals who have given their
consent participate in the studies and that subjects are free to withdraw from participation during the course of an
investigation if they so wish. The application of these principles is described in annex A.
The protocol should describe any arrangements for medical fitness assessment or health monitoring and identify an
independent medical officer responsible for the implementation of these arrangements. The medical officer may
advise on any likely risks to the subjects and on the level of fitness assessment and monitoring appropriate to the
intended study. The medical officer may delegate specific duties to appropriately qualified individuals, for example,
health monitoring during exposures may best be done by experienced laboratory staff with appropriate training in
first aid and basic resuscitation techniques. The medical officer will act as the final arbiter in questions of fitness of
particular individuals to participate in a study.
The medical officer should have practical experience of observing the effects of thermal stress on people, as well
as a sound theoretical knowledge of these effects. This may be obtained by cooperation with a research team, or in
the course of formal training in applied physiology or related disciplines.
4.2.2.2 Medical fitness assessment
Medical fitness assessment should take place prior to exposure to extreme hot or cold environments. This should
take account of the intended exposure conditions and is centred on the individual. It is intended to determine
ISO 12894:2001(E)
whether there are any reasons to consider that the person may be susceptible to ill effects from the planned
environmental exposure.
Assessment may be by questionnaire and medical examination and advice is given in informative annexes C and D
on when these options may be appropriate. If physiological measurement is to be used during exposure, either to
support health monitoring or to collect information, then simple initial health checks may also be required, see
informative annex E.
A questionnaire should always be completed and the option for a medical examination should be followed in every
case where there is any doubt about the fitness of an individual. Examination allows an assessment of the
psychological suitability of an individual which cannot be judged from responses to a questionnaire.
Where assessment is by questionnaire and this does not reveal any medical factor which may predispose an
individual to ill effects, he or she may be accepted as a subject. Where results suggest a possible predisposition,
an individual should only be accepted on the advice of a medical officer who may ask to examine the individual or
to obtain an opinion from a relevant specialist.
4.2.2.3 Health monitoring
Assessment of the anticipated physiological strain, coupled with appropriate medical fitness assessment will, in
most situations, provide adequate safeguards against the risk of illness occurring from exposure to hot or cold
conditions. In the more extreme conditions, to which this International Standard applies, and particularly in
exposures to heat, the onset of ill health and the occurrence of symptoms may be rapid and some form of health
monitoring is likely to be required to detect these changes and allow an early intervention. An example might be
where the prediction of physiological strain is not practicable due to the type of clothing to be worn.
The level of health monitoring required will depend on the detailed circumstances of exposure. The minimum
possible is the observation of the subjects by someone with experience of the effects of heat or cold on the body. In
many cases, the measurement of physiological parameters will form part of the experimental protocol and the data
collected will be used in the results of the study. If not already required for this reason, monitoring of core and skin
temperatures, heart rate and, in some cases, blood pressure is likely to be required as these factors may be
limiting. Upper limits for withdrawal of subjects from exposure should be decided as part of the experimental
protocol.
In most cases, it will be adequate for the monitoring to be done by a trained non-medical person and to have
access to the opinion of a medical officer but, in more severe conditions, it will be prudent for the medical officer, or
another appropriately trained person (such as an emergency medical technician or paramedic), to be available to
attend promptly to a casualty if required. Whether or not a medical officer is available to assist in monitoring and
treatment, it will be necessary to have arrangements in place for the rapid removal of a casualty to a hospital with
emergency facilities. More detailed advice on the appropriate level of monitoring is given in informative annexes C
and D.
During any prolonged series of experiments in which behavioural changes could occur in the subjects, there should
be arrangements in place to allow the experimenter and the independent medical officer to obtain the advice of a
psychologist.
4.2.3 Field investigations
Ergonomic investigations made in the field should conform to the same ethical guidelines provided for laboratory-
based studies. Where volunteers who are not normally employed in the work task act as subjects, the requirements
for medical fitness assessment and health monitoring are as described in 4.2.2.2 and 4.2.2.3.
Where workers regularly employed in the task under investigation are the subject of study, the requirements for
medical supervision should be agreed with the occupational physician responsible for the health of the workers.
The requirements will be based on those described in 4.3, taking account of the effect of the study on normal work
practices and of the views of workers and their representatives.
4 © ISO 2001 – All rights reserved

ISO 12894:2001(E)
4.2.4 Practical implementation of medical supervision
Advice on the practical requirements of medical supervision in the laboratory, or during field studies with volunteers
not normally exposed to the conditions, can be found in informative annex E.
4.3 Occupational exposure
4.3.1 General
Medical supervision of workers who may be exposed to very hot or cold conditions at work should form part of their
normal occupational health care and should take account of national health and safety legislation. Work
environments are generally less predictable than those used in laboratory investigations and some jobs may
require high rates of energy expenditure and the use of protective clothing. In these circumstances, endogenous
heat production contributes significantly to the resulting heat strain.
A risk assessment should be undertaken for all occupational exposures to extreme thermal environments. This
should allow an evaluation of the likely physiological strain of the task to be made, before the work actually begins.
Also, it should allow the available means of reducing this physiological strain to be identified. Work tasks should not
be designed in a way which permits unacceptable physiological strain to occur, for example, no work should be
planned in which the risk assessment shows that there is a significant potential for general hypothermia to occur.
However, where outdoor work takes place, it will not always be possible to entirely eliminate such risks, for
example, during fishing, forestry or agriculture in cold temperate or sub-arctic climates, or during construction work
in tropical latitudes.
Work which carries a risk of heat strain must be carefully controlled. Heat strain may however be expected to occur
in some emergency situations, such as rescue work in mines. The level of fitness assessment and health
monitoring should be matched to the circumstances of exposure and general guidance is given in annex F.
4.3.2 Medical fitness assessment
This will be determined by the occupational physician responsible for the workforce in the context of relevant
national legislation and guidance. All the components of the job should be taken into account and this may include
the need to respond to emergency situations. Direct health monitoring will often be impractical in work tasks,
therefore adequate fitness assessment with proper control of exposure will form the basis for the prevention of ill
health from exposure to heat or cold at work.
4.3.3 Health monitoring
After appropriate medical fitness assessments have been completed, health monitoring may still be required in
some occupational situations where exposure is extreme. Further advice is contained in informative annex F.
Information on any acute ill health which occurs during exposures should be reported back to the occupational
physician with responsibility for the workers.
ISO 12894:2001(E)
Annex A
(informative)
General principles underlying ergonomic investigations in which volunteer
subjects may experience discomfort
A.1 General principles
In this annex the general principles relating to the ethics of experimentation on human subjects are described.
Reference should also be made to relevant national codes or regulations or other international guidance. (See the
bibliography).
Within the field of ergonomics, it is of legitimate interest to study the boundaries of environmental conditions which
individuals can safely tolerate and also the effects of such environmental conditions on the performance of mental
and physical tasks. Such studies are usually best conducted in the laboratory, in which exposure can be carefully
controlled and responses closely monitored. These studies are often conducted with volunteers with no previous
experience of the environmental stresses to be studied, or the measurement techniques to be used. Such studies
are considered to be ethically acceptable if they comply with certain general principles.
There must be a genuine expectation of increased scientific knowledge on completion of the study. In the case of
teaching demonstrations using standard procedures, the benefit is in the increased knowledge and experience of
the students concerned. The level of benefit in terms of increased knowledge should outweigh the discomfort
experienced by the subjects. Thus it will not normally be acceptable to submit volunteers to great discomfort,
unless the information to be obtained is considered to be of high practical or theoretical value.
The study must be planned using current knowledge of the problem being investigated and the methodology
proposed must be suitable to obtain the required information. This should not be extended to obtain information
which may be only “of interest”, in other words, all the data collected should be directly relevant to the object of the
experiment.
No serious risk to the health or personal safety of the subjects should be foreseeable. Although studies should be
designed so as to minimize such risks, individuals will vary in their tolerance to the environmental conditions and
the resulting discomfort. They should be free to withdraw from the study if they so wish, at any time and without the
need to give any explanation.
The investigator must have access to adequate facilities to conduct the experiment successfully and to provide for
the welfare of the subjects. This will include suitable changing rooms and areas where instrumentation can be
applied in privacy as well as areas for subjects to rest and recover after an experiment.
The protocol for the investigation should be submitted to a research ethics committee for approval, and due
account taken of any comments made by the committee. The protocol should include an assessment of the
severity of the environmental exposure on the subjects, information on any potential risks to health, and details of
the arrangements proposed for fitness assessment and health monitoring of the subjects, where this is appropriate.
The protocol should also include information about the arrangements which have been made for financial
compensation of a subject in the event that any injury or harm to health occurs. It is recommended that laboratories
have appropriate insurance to cover this eventuality.
Volunteer subjects should give their written consent to participate in the study. Consent is only valid if it is both true
and informed. For consent to be true, there should be no factor which might unfairly influence the decision of the
individual to participate, either in the relationship between the investigator and the potential subject, or in the
remuneration which may be offered. A suggested form of written consent is given in A.2. Particular care should be
taken to ensure that no pressure to participate is exerted on individuals in a subordinate position to the investigator,
such as students or junior members of staff.
6 © ISO 2001 – All rights reserved

ISO 12894:2001(E)
For consent to be informed, the investigator should explain to the potential subject the purpose of the investigation,
the methodology to be used, the level of discomfort to be expected and any foreseeable risks. Such explanations
should be available to the potential subject in writing. Also, it must be made clear to volunteers that they are free to
withdraw their consent at any time, including during the course of an experimental session.
Individuals who take part in studies also have responsibilities towards the investigators. They should comply with
the instructions given to them, particularly in relation to behaviours to avoid prior to attending for experimental
sessions, for example, not smoking or not consuming alcohol or caffeine. Participation in more than one
experimental investigation at the same time may invalidate the results of one or both of the studies and may
present a risk to the individuals themselves. Subjects should not attempt to participate in more than one study at
the same time, and must not do so without obtaining the approval of the investigators in both studies.
A.2 Example of a consent form for a volunteer subject in an ergonomic investigation
involving exposure to heat or cold
IN CONFIDENCE
Name . Age . years Sex: Male/Female
Normal medical adviser. Name .
Address .
....................................................................................................................................................................
1. I am willing to participate as an experimental subject in the study of
..............................................................................................................................................................................
to be conducted by .
at .
2. I have received an explanation of the nature and purpose of this study and of any risks to my health which
are foreseen.
3. I agree to provide accurate information about my health and to be medically examined if this is considered
necessary. I agree that my normal medical adviser can provide information about my medical history to the
authorized medical adviser to the study (independent medical officer). I understand that all information about
my health will be treated in confidence.
4. I agree to cooperate fully with the investigators and not knowingly to do anything which might invalidate the
results.
5. During the course of the investigation to which I am now giving my consent, I will not participate as a subject
in any other study, without first informing the investigators and obtaining their approval, which may be
withheld.
6. I understand that I am free to withdraw my consent to participate in the study at any time without the need to
give an explanation for my decision.
Signed . Date .
ISO 12894:2001(E)
Statement by investigator
In connection with the study described above, I have explained to . the nature and purpose of the
study and the foreseeable risks from participation in the study. I have explained that the decision to volunteer does
not affect the right to compensation in the event of illness or injury.
Signed . Date .
8 © ISO 2001 – All rights reserved

ISO 12894:2001(E)
Annex B
(informative)
Medical effects of exposure to hot and cold
B.1 General
This annex provides an introduction to the subject which should be supplemented by reference to standard
textbooks of physiology, medicine and first aid. These notes are provided for information only and on their own do
not provide a sufficient basis on which to plan the treatment of casualties suffering from the effects of exposure to
extreme heat or cold.
B.2 Heat disorders and their immediate treatment
B.2.1 General
The main disorders arising from exposure to heat are usually classified into the categories described in B.2.2 to
B.2.7. These categories probably represent a continuum of effect of increasing severity and, if early signs are not
detected and treated, individuals will be at risk of more serious illness. The essential treatment of heat disorders,
other than a simple faint, is to reduce the body core temperature. Any episode of altered consciousness level in an
individual exposed to heat should be taken as a sign of heat hyperpyrexia even if the body core temperature is not
found to be significantly elevated.
Other disorders which may arise due to heat are heat hyperventilation, heat oedema, heat cramps and prickly heat.
An individual who has suffered a heat disorder should be medically assessed prior to any further heat exposure.
In heat exposures where health monitoring is required, adequate facilities to treat heat disorders should be
available. This will include a couch or bed on which to let a person rest, a strong electric fan, a source of tepid
water and sheets and sponges. A bath or shower may also be desirable.
Equipment should be available to allow a clinical examination and for a doctor, nurse or other competent person
(emergency medical technician/paramedic) to be able to monitor the casualty's pulse, blood pressure and rate and
depth of respiration. A high-reading metal-stemmed thermometer should be available to measure rectal
temperature if core temperature is not otherwise monitored. There is no advantage in having equipment available
for advanced resuscitation, for example, by laryngeal intubation unless the medical officer concerned is competent
in the use of these techniques.
With heat casualties, the priority for treatment is to lower the body core temperature and, if necessary, transfer the
person to hospital. This must be considered in any case where the person shows no sign of rapid recovery, either
of consciousness level and clinical condition, or to a lower body core temperature. Body cooling can be continued
during transfer of the casualty to a medical facility.
B.2.2 Heat hyperpyrexia (“heat stroke”)
This potentially fatal condition occurs when body core temperature is raised above a value of approximately 41 °C,
although the clinical condition is not precisely linked to recorded core temperature. Its onset may be sudden, being
indicated by collapse of the individual who will often, but not invariably, have a hot, red, dry skin. The
consciousness level is likely to be impaired and the pulse is rapid and weak. The condition results from a failure of
the body's thermoregulatory mechanism to match the body's cooling requirements and if the individual is not
removed from the heat, and actively cooled, brain damage or death can arise from the elevated tissue
temperatures.
ISO 12894:2001(E)
First aid: This is a medical emergency. Remove the casualty from the heat and remove the clothing. Take
measures to cool the casualty. If unconscious, lie him in the three-quarters prone (“recovery”) position and cover
with a wet sheet, blowing air over the body with a fan. Tepid sponging can also be used. If conscious, use a tepid
bath or shower, massaging the skin to stimulate the circulation. Medical, or paramedical, assistance should be
summoned but the priority is to cool the casualty. Immediate medical treatment may include the administration of
large volumes of intravenous fluids. Ice, or very cold water, is not normally recommended to be used for cooling as
superficial vasoconstriction can prevent loss of heat from the skin surface.
B.2.3 Heat exhaustion
This results from a combination of thermal and cardiovascular strain. The individual becomes tired and stumbling,
with poor control and coordination, and is irritable. The pulse is rapid and may be bounding or weak. The
peripheries are pale and moist and respiration is shallow and rapid. Dehydration or, less commonly, salt deficiency
may contribute to the onset of heat exhaustion, which may, in turn, predispose to the onset of heat hyperpyrexia or
to other accidents. If, during heat exposure, sweat losses are replaced with very large quantities of water, it is
possible to lower the sodium concentration in the blood. This may result in a reduction in the peripheral circulation.
First aid: Remove the person from the heat, loosen clothing and allow to recover in a cool place. This can be
assisted by fanning or tepid sponging. Oral fluids can be given if conscious, with added salt if excessive ingestion
of water alone can have contributed to the collapse. In more severe cases, immediate medical treatment will
include the administration of intravenous fluids as for heat hyperpyrexia and probably transfer to hospital.
B.2.4 Heat syncope
This is a simple faint as a result of reduced effective circulating blood volume and may occur at core temperatures
below 38 °C. It is more likely to occur in the unaclimatized during early exposure to heat, before the cardiovascular
system has had time to adapt. It can be serious if the body is held upright, for example due to work in confined
spaces, in which case brain damage or death may result.
First aid: Allow the person to lie down to recover.
B.2.5 Heat hyperventilation, tetany
This can arise as a result of hyperventilation in the heat, especially where respiratory protective equipment is being
worn. It is a consequence of respiratory alkalosis due to the increased loss of carbon dioxide. It is not serious if
recognized and treated, but can be very
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