SIST EN 28996:2001

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Ergonomie - Bestimmung der Wärmeerzeugung im menschlichen Körper (ISO 8996:1990)Ergonomie - Détermination de la production de chaleur métabolique (ISO 8996:1990)Ergonomics - Determination of metabolic heat production (ISO 8996:1990)13.180ErgonomijaErgonomicsICS:Ta slovenski standard je istoveten z:EN 28996:1993SIST EN 28996:2001en01-marec-2001SIST EN 28996:2001SLOVENSKI
STANDARD



SIST EN 28996:2001



SIST EN 28996:2001



SIST EN 28996:2001



INTERNATIONAL STANDARD IS0 8996 First edition 1990-12-15 Ergonomics - Determination of metabolic heat production Ergonomie - D&ermina tion de la production de chaleur mktabolique Reference number IS0 8996 : 1990 (E) SIST EN 28996:2001



lSO8996:1990 (E) Foreword IS0 (the International Organization for Standardization) is a worldwide federation of national standards bodies (IS0 member bodies). The work of preparing International Standards is normally carried out through IS0 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, govern- mental and non-governmental, in liaison with ISO, also take part in the work. IS0 collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. 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. International Standard IS0 8996 was prepared by Technical Committee lSO/TC 159, Ergonomics, Sub-Committee SC 5, Ergonomics of the physical environment. Annexes A to G form an integral part of this International Standard. 0 IS0 1990 All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the publisher. International Organization for Standardization Case postale 56 l CH-1211 Geneve 20 l Switzerland Printed in Switzerland ii SIST EN 28996:2001



IS0 8996 : 1990 (El Introduction This International Standard is one of a series intended for use in the study of thermal environments. It covers the evaluation of metabolic heat production by determining the metabolic rate needed to evaluate comfort and thermal stress using the methods given in this series of International Standards. . . . Ill SIST EN 28996:2001



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INTERNATIONAL STANDARD IS0 8996 : 1990 (El Ergonomics - Determination of metabolic heat production 1 Scope The metabolic rate, as a conversion of chemical into mechanical and thermal energy, measures the energetic cost of muscular load and gives a numerical index of activity. A knowledge of metabolic rate is necessary to measure metabolic heat production for the evaluation of human heat regulation. Specifying methods for determination metabolic rate, this In- ternational Standard can also be used for other applications - for example: the assessment of working practices, the cost of specific jobs or sport activities, the total cost of activity, etc. 2 Normative references The following standards contain provisions which, through reference in this text, constitute provisions of this International Standard. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent editions of thti standards indicated below. Members of IEC and IS0 maintain registers of currently valid International Standards. I SO 7933 : 1989, Hot environments - Analytical determination and interpretation of thermal stress using calculation of re- quired sweat rate. IS0 9886 : - 11, Ergonomics - Evaluation of thermalstrain by physiological measurements . 3 Principle and accuracy Since most of the energy produced by an organism is con- verted into thermal energy, the mechanical fraction - called the “useful work” (w) - can normally be neglected and the metabolic heat production can be equated with the metabolic rate (see IS0 7933). Table 1 gives three approaches for determining metabolic rate. Table 1 - Levels for the determination of the metabolic rate Level I Method A - Classification according to kind of activity B - Classification according to occupation Accuracy Rough information where the risk of error is very great II A - Use of tables of group assessment B - Use of estimation tables for specific activities C - Use of heart rate under defined conditions High error risk Accuracy: * 15 % III Measurement Risk of errors within the limits of the accuracy of the measurement and of the time study Accuracy: & 5 % Inspection of the work place Not necessary information on technical equipment, work organization Time study necessary Not necessary Time study necessary I) To be published. SIST EN 28996:2001



IS0 8996 : 1990 (El At level I, two methods are given for the estimation of metabolic rate. Method A is a classification according to the kind of activity, method B is a classification according to occupation. Both methods provide a rough estimate and there is considerable scope for error. This limits their accuracy considerably. At this level an inspection of the work place is not necessary. metabolic rate, moderate metabolic rate, high metabolic rate, very high metabolic rate). The examples given in annex A, table A.1, include short rest pauses and illustrate the classifi- cation. 4.2 Table for the estimation of metabolic rate by occupations At level II, using method A, the metabolic rate is determined by adding the basal metabolic rate to the metabolic rate for body posture, the metabolic rate for type of work and the metabolic rate for body motion related to work speed (tables of group assessment). Using method B the metabolic rate is determined by means of the tabulated values for various activities. The possibility that errors may arise is high. A time study is necessary to determine the metabolic rate of work which in- volves a cycle of different activities. Using method C the metabolic rate is determined by measuring heart rate. This method for indirect determination of metabolic rate is based on the relationship between oxygen uptake and heart rate under defined conditions. Annex B, table B. 1 shows the metabolic rate for some different occupations. The values are mean values for the whole working time, but without considering longer rest pauses, for example, lunch time. Significant variation may arise due to differences in technology, work elements, work organization, etc. 4.3 Tables for the es bY task-components ti matio n of metabolic rate The metabolic rate of a man at work may be estimated by adding its various components. An inspection of the work place is usually necessary for this purpose. At level Ill the metabolic rate is determined by direct measure- ment. A d etailed time study is necessary during measurement. The meta bolic rate is valu es of the following analytically determined by adding the The accuracy of each method is limited by several factors. When looking at a single person performing a the main factors can be described as follows. task at one time a) basal metabolic rate; b) the component for body posture; NOTE - The accuracy values given in table 1 take these factors into account. cl the component for type of work; In the case of the tables, differences between the observers and their level of training mainly influence the results. Using method C of level II, the accuracy of the relationship between oxygen uptake and heart rate because of existing other stress factors, which cannot be neglected, must be taken into ac- count. d) the component for body motion related to work speed. The basal metabolic rate is the metabolic down at rest under defined conditions. rate of a person lying The basal metabolic rate (BM) is a function of weight, height, age and sex. As these factors have little influence on BM, values of 44 W/m2 for men and 41 W/m2 for women can be used as a good approximation. In order to give comparable values, the values in this International Standard refer to a stan- dard person, defined in annex C, table C.1. Cultural differences also influence the results. At level III, the measurement accuracy (determination of gas volume and oxygen fraction) will determine the degree of error. In case of standardization of the resul ts - for example statement relating to work places - other factors sue general as - individual variability In annex D, table D.l gives the metabolic rate for body pos- ture, table D.2 the metabolic rate for different types of work and table D.3 the metabolic rate for body motion related to work speed. Tables D.4 and D.5 give some examples of the use of this method. - differences in work equipment differences in work speed differences in work technique influence the possible accuracy of each method (see 4.6.2). 4.4 Table indicating the metabolic rate for typical activities Thus the accuracy of the results and also the costs involved increase from level I to level Ill. Direct measurement gives the most accurate values. As far as possible the most accurate method should be used. Values of metabolic rate may be obtained from table E. 1. These values are based on measurements. annex E, 4.5 Metabolic rate of a work cycle 4 Tables for the estimation of metabolic rate To determine the overall metabolic rate of a work cycle it is necessary to carry out a time and performance study which includes a detailed description of the work. This involves classi- fying each activity, and taking account of factors such as the duration of each activity, the distances walked, heights climbed, weights manipulated, the number of actions carried out, etc. 4.1 Classification of metabolic rate by kinds of activities The metabolic rate can be estimated approximately using the classification given in annex A. Here the metabolic rate for a given activity is classified into one of five classes (resting, low 2 SIST EN 28996:2001



IS0 8996 : 1990 (El The metabolic rate for a work cycle can be determined from the metabolic rate of the respective activity and the respective duration from the equation .” 4.6.4 Influences of the length of rest periods and work r1 1 c M=- Miti T i= 1 Tables D.l to D.5 and table E.l (see 4.3 and 4.4) cannot be applied to an intermittent sequence of short activities and . . . (1) longer rests because this leads to higher levels of metabolic rate. The limits are shown in figure ‘l where the hatched area shows the region in which the tables (see 4.3 and 4.4) cannot be used. Figure 1 only applies when the muscles are completely where relaxed during a rest period. M is the average metabolic rate of the work cycle, in watts per square metre; Mi is the metabolic rate of the respective activity, in watts per square metre; T is the duration, in seconds, of the considered work cycle ; Example I (see figure 1) shows a work rhythm of 8 min of resting time to 1 min of working time. In this case the metabolic rate tables (see 4.3 and 4.4) cannot be used. For activities showing a proportion of working time within the white field, as shown in example 2, the tables can be used safely. As an increase in the metabolic rate due to the Simonson Effect depends on the type of work and the muscle groups used, further information on this problem is not given on account of ti is the duration, in seconds. of the respective activity. Annex F gives an example. 4.6 Requirements for the application of metabolic rate tables its complexity. 4.6.5 Interpolation of the values 4.6.1 Standardization of values Interpolation of metabolic rate values is possible. Where work- ing speeds differ from those given in the tables (see 4.3 and Values have been standardized with respect to the standard person defined in annex C to allow a comparison of values from different sources. 4.4), conversion is only possible within a range of Ifr 25 % of the indicated speed. 5 Measurement of metabolic rate This is necessary for particular activities which require a move- ment associated with the body weight, for example walking upwards or lifting weights. 5.1 Direct determination of metabolic rate 4.6.2 Variation of values The methods of measurement described below were checked in many field studies and laboratory analyses; other methods The values indicated vary within certain limits due to the have to be verified by the collected data using this method. influence of the following factors: 5.1 .I Methods of measurement a) work technique; The metabolic rate can be determined by two principal methods : b) work speed ; partial method; cl differences between the work equipment. - - integral method. The partial method shall be used for light and moderately heavy work, the integral method shall be used for heavy work of short duration. Different methods have to be used for the following reasons. In the case of light and moderately heavy work the oxygen uptake reaches the oxygen requirement after a short period of work. The oxygen uptake reaches a steady state and equals the oxygen requirement. In the case of heavy work, oxygen requirement is above the long-term limit of aerobic power and, in the case of very heavy work, above the maximal aerobic power. During heavy work, oxygen uptake cannot reach oxygen requirement. The oxygen deficit is balanced after work ceases. Thus, the measurement includes the working and the subsequent resting period. The integral method should be used for an oxygen consumption of more than 60 litres of oxygen per hpur (60 I 02/h), equivalent to 1 litre of oxygen per minute. For the same work and under the same working conditions the metabolic rate can vary from person to person by about IL 5 %. For someone used to the activity, the variation is about 5 % under laboratory conditions. Under field conditions, i.e. when the activity to be measured is not exactly the same from test to test, a variation up to 20 % or more can be expected. 4.6.3 Influence of climate The metabolic rates given in this International Standard apply to moderate thermal environments. In a hot or cold environ- ment the metabolic rate may increase. In hot conditions a maximum increase of 5 W/m to IO W/m2 may be expected due to increased heart rate and sweating. In cold conditions a maximum increase of up to 200 W/m2 may be expected when shivering occurs. The wearing of heavy clothing will also increase metabolic rate. Figure 2 shows the procedure followed using the partial method. The work begins first without collecting any expired air. 3 SIST EN 28996:2001



IS0 8996 .” 1990 (E) metabolic rate 12 IO 8 6 4 2 5 Duration of work, min Figure 1 - Domain of the increase in metabolic rate 02 deficit 02 debt repayment Figure 2 - Measurement of metabolic rate using the partial method SIST EN 28996:2001



IS0 8996 : 1990 (El Since the steady state is reached after 3 min to 5 min, the col- lection of expired air starts, without interrupting the work, after about 5 min (preliminary period). The work continues for 5 min to 10 min (main period). Gas collection, either complete - for example with a Douglas bag - or regular sampled - for example with a gas meter, stops when work ceases. Thus a part has been removed from the “steady-state” of the work. When using the partial method it is essential that the metabolic rate during work be less than the long-term stress limit. With the integral method (see figure 3), expired gas collection is started immediately at the beginning of the work, and the work continues for a certain time, usually for not more than 2 min to 3 min (main period). At the end of the work the sub- ject sits down, while the measurement continues until the resting value is attained. During this recovery period, the oxygen debt incurred during the work is repaid. Since the measurement includes the working (main period) and sitting (recovery period) activity, the metabolic rate needed for sitting has to be subtracted from the measured value in order to obtain the metabolic rate related to work alone (see 5.1.4.2). It is necessary to record the course of the work (time study) and the frequency of repeated activities, etc., for the further evalu- ation of the results and for the comparison of the metabolic rate with data in the literature. Examples of the calculation of metabolic rate are given in annex G. 51.2 Determination of metabolic rate from oxygen consumption Since the human body can only store very small amounts of oxygen, it must be continuously taken up from the atmosphere by respiration. Muscles can work for a short time without being directly provided with oxygen (anaerobic work), but for longer periods of work, oxidative metabolism is the major energy source. The metabolic rate can be determined, therefore, by measuring oxygen consumption. The energetic equivalent (EE) for oxygen is used to convert oxygen consumption into metabolic rate. The energetic equivalent depends on the type of metabolism which is indicated by the respiratory quotient (RQ) [see equa- tion (2)l. In the determination of the metabolic rate, the use of a mean RQ of 0,85 and thereby of an energetic equivalent (EE) of EE = 5,68 W.h/l O2 is often sufficient. In that case, measurement of carbon dioxide production is not required. The maximum possible error is IL 3,5 %, but generally the error will not exceed 1 %. Thus the metabolic rate can be determined from equations (2), (3) and (4) EE = (0,23 RQ + 0,77) x 5,88 . . . (2) 02 requirement Maximal aerobic power FA 02 deficit 02 debt repayment Basal metabolic rate Measurement Main Recovery period period Figure 3 - Measurement of metabolic rate using the integral method 5 SIST EN 28996:2001



IS0 8996 :1990 (E) ko2 RQ = 7 . . . v02 (3) 1 M = EE x Vo2 x - . . . AD, (4) where EE is the energetic equivalent, in watts hours per litre of oxygen ; RQ is the respiratory quotient; v02 is the oxygen consumption, in litres of oxygen per hour; Vcoz is the carbon dioxide production, in litres of carbon dioxrde per hour; M is the metabolic rate, in watts per square metre; AD, is the body surface, in square metres, according to Du Bois; ADu = 0,202 x w,“,425 x H,of725 where Wb is the body weight, in kilograms; I-& is the body height, in metres. 5.1.3 Determination of oxygen uptake It is necessary to measure or to record the following data to determine oxygen uptake : a) personal data: sex, weight, height, age; b) method of measurement; c) duration of the measurement; 1) partial method: main period, 2) integral method: main and subsequent period; d) atmospheric pressure; e) volume of air expired; f) temperature of the expired air; g) fraction of oxygen in the expired air if determination of RQ is required; h) fraction of carbon dioxide in the expired air. 5.1.3.1 Calculation of the STPD reduction factor The gas volume shall be related to t = 0 OC, p = 101,3 kPa (normal pressure) for a dry gas (STPD conditions: Standard condition for Temperature OC, barometric Pressure 101,3 kPa, Dry). As the collected air is saturated with water vapour (the saturation pressure of which is a function of temperature) and its temperature is determined by ambient temperature (ATPS conditions : Atmospheric condition for Temperature and barometric Pressure, Saturated), the reduction factorf can be calculated from the following equation using the partial pressure of the water vapour (see table 2). f 273 b - PH20) = (273 + t) 101,3 where . . . (5) f is the STPD reduction factor; p is the measured atmospheric pressure, in kilopascals; PH20 is the partial pressure of the saturated water vapour, in kilopascals (see table 2); t is the temperature of the expired air, in degrees Celsius, measured in the gas-meter or assumed to be ambient temperature when a Douglas bag is used. If the collected expired air is heated up by the environment to a temperature in excess of 37 OC, the pressure of the saturated water vapour at a temperature of 37 OC shall be used: t < 37 OC (see table 2) t > 37 OC PH20 = 6,27 kPa 5.1.3.2 Calculation of the expiration volume for STPD Vex STPD = V,,ATPS x f . . . (6) where Vex STPD is the expiration volume, in litres, at STPD; Vex ATPS is the expiration volume, in litres, at ATPS; f is as defined in 5.1.3.1. Table 2 - Pressure of saturated water vapour
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