ISO/TS 16976-1:2015

TECHNICAL ISO/TS
SPECIFICATION 16976-1
Second edition
2015-12-01
Respiratory protective devices —
Human factors —
Part 1:
Metabolic rates and respiratory flow
rates
Appareils de protection respiratoire — Facteurs humains —
Partie 1: Régimes métaboliques et régimes des débits respiratoires
Reference number
ISO/TS 16976-1:2015(E)
©
ISO 2015

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ISO/TS 16976-1:2015(E)

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ISO/TS 16976-1:2015(E)

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Activity and metabolic rate . 2
5 Metabolic rate and oxygen consumption . 4
6 Oxygen consumption and minute volume. 5
7 Minute volume and peak inspiratory flow rates . 7
7.1 Normal breathing. 7
7.2 Speech and breathing . 8
7.3 Sneezing and coughing .10
8 Individual variation and gender aspects .12
Annex A (informative) Examples for the use of data .15
Bibliography .18
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ISO/TS 16976-1:2015(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.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the meaning of ISO specific terms and expressions related to conformity
assessment, as well as information about ISO’s adherence to the WTO principles in the Technical
Barriers to Trade (TBT) see the following URL: Foreword - Supplementary information
The committee responsible for this document is ISO/TC 94, Personal safety — Protective clothing and
equipment, Subcommittee SC 15, Respiratory protective devices.
This second edition cancels and replaces the first edition (ISO/TS 16976-1:2007), of which it constitutes
a major revision with the following technical change:
— 7.3 has been added.
ISO/TS 16976 consists of the following parts, under the general title Respiratory protective devices —
Human factors:
— Part 1: Metabolic rates and respiratory flow rates [Technical Specification]
— Part 2: Anthropometrics [Technical Specification]
— Part 3: Physiological responses and limitations of oxygen and limitations of carbon dioxide in the
breathing environment [Technical Specification]
— Part 4: Work of breathing and breathing resistance: Physiologically based limits [Technical Specification]
— Part 5: Thermal effects [Technical Specification]
— Part 6: Psycho-physiological effects [Technical Specification]
— Part 7: Hearing and speech [Technical Specification]
— Part 8: Ergonomic factors [Technical Specification]
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ISO/TS 16976-1:2015(E)

Introduction
For an appropriate design, selection, and use of respiratory protective devices, it is important to
consider the basic physiological demands of the user. The type and intensity of work affect the metabolic
rate (energy expenditure) of the wearer. The weight and weight distribution of the device on the human
body also may influence metabolic rate. Metabolic rate is directly correlated with oxygen consumption,
which determines the respiratory demands and flow rates. The work of breathing is influenced by the
air flow resistances of the device and the lung airways. The work (or energy cost) of a breath is related
to the pressure gradient created by the breathing muscles and the volume that is moved in and out of
the lung during the breath. Anthropometric and biomechanical data are required for the appropriate
design of various components of a respiratory protective device, as well as for the design of relevant
test methods.
This part of ISO/TS 16976 is the first part of a series of documents providing basic physiological and
anthropometric data on humans. It contains information about metabolic rates and respiratory flow
rates for various types of physical activity.
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TECHNICAL SPECIFICATION ISO/TS 16976-1:2015(E)
Respiratory protective devices — Human factors —
Part 1:
Metabolic rates and respiratory flow rates
1 Scope
This part of ISO/TS 16976 provides information on factors related to human anthropometry, physiology,
ergonomics, and performance for the preparation of standards for performance requirements, testing,
and use of respiratory protective devices. This part of ISO/TS 16976 contains information related to
respiratory and metabolic responses to rest and work at various intensities. Information is provided for
the following:
— metabolic rates associated with various intensities of work;
— oxygen consumption as a function of metabolic rate and minute ventilation for persons representing
three body sizes;
— peak inspiratory flow rates during conditions of speech and no speech for persons representing
three body sizes as a function of metabolic rates.
The information contained within this part of ISO/TS 16976 represents data for healthy adult men and
women of approximately 30 years of age, but is applicable for the age range of the general population.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
ISO 8996:2004, Ergonomics of the thermal environment — Determination of metabolic rate
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
aerobic energy production
biochemical process in the human cells that delivers energy by combustion of fat, carbohydrates and, to
a lesser extent, protein in the presence of oxygen, with water and carbon dioxide as end products
3.2
anaerobic energy production
biochemical process in the human cells that delivers energy by combustion of carbohydrates without
oxygen, with lactic acid as the end product
3.3
ambient temperature pressure saturated
ATPS
standard condition for the expression of ventilation parameters related to expired air
Note 1 to entry: Actual ambient temperature and atmospheric pressure; saturated water vapour pressure.
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3.4
ambient temperature pressure humidity
ATPH
standard condition for the expression of ventilation parameters related to inspired air
Note 1 to entry: Actual ambient temperature, atmospheric pressure and water vapour pressure.
3.5
breath cycle
respiratory period comprising an inhalation and an exhalation phase
3.6
body temperature pressure saturated
BTPS
standard condition for the expression of ventilation parameters
Note 1 to entry: Body temperature (37 °C), atmospheric pressure 101,3 kPa (760 mmHg), and water vapour
pressure (6,27 kPa) in saturated air.
3.7
peak inspiratory flow rate
highest instantaneous flow rate during the inhalation phase of a breath cycle
Note 1 to entry: It is expressed in l/s BTPS.
Note 2 to entry: L/s is the preferred unit as the flow takes place during only a short fraction of the breath cycle.
3.8
minute ventilation
V
E
total volume of air inspired (or expired) in the lungs during 1 min
Note 1 to entry: It is expressed in l/s BTPS.
3.9
oxygen consumption
V
O2
amount of oxygen consumed by the human tissues for aerobic energy production
Note 1 to entry: It is expressed in l/min STPD.
3.10
physical work capacity
ability of a person to engage in muscular work
3.11
standard temperature pressure dry
STPD
standard conditions for expression of oxygen consumption
Note 1 to entry: Standard temperature (0 °C) and pressure (101,3 kPa, 760 mmHg), dry air (0 % relative humidity).
4 Activity and metabolic rate
Users of respiratory protective devices (RPD) perform physical work at various intensities. Physical
work, in particular when associated with large muscle groups as is the case with firefighting, requires
high levels of metabolic energy production (metabolic rate). The energy is produced in human cells by
aerobic or anaerobic processes.
Aerobic energy production is by far the most common form of energy yield for all types of human cells.
It is also the normal form of energy production for the muscles. Depending on physical fitness and other
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factors, humans can sustain high levels of aerobic energy production for long periods of time. Very high
activity levels, however, can only be sustained for short periods of time (minutes) and they also engage
the anaerobic energy yielding processes. The associated production of lactic acid is one reason for the
early development of fatigue and exhaustion.
Aerobic energy production is strictly dependent on the constant delivery of oxygen to the active
cells. Oxygen is extracted from inspired air, bound to haemoglobin in red blood cells in the alveolar
capillaries and transported to the target tissues via the circulation. Consequently, there is a direct,
linear relationship between the rate of oxygen consumption and the metabolic rate. The relationship is
described in ISO 8996.
Table 1 of this part of ISO/TS 16976 is derived from ISO 8996:2004, Table A.2, which defines five classes
of metabolic rate. This table forms the basis for developing a standard for the assessment of heat stress.
The classes represent types of work found in industry. The figures represent average metabolic rates
for work periods or full work shifts, generally including breaks. Metabolic rate shall not be confused
with external work rates, such as those defined on a bicycle ergometer.
Rescue work and firefighting are by nature temporary and often unpredictable. Activities may become
very demanding and high levels of metabolic rate have been reported in References [1], [13], [14], [16],
[17], [21], [23], and [25]. According to Reference [21], mean values for oxygen uptake of between 40 ml/
(kg × min) and 45 ml/(kg × min) are reported for the most demanding tasks in firefighting drills (see
References [6], [8], and [13]). Assuming an average body weight of 80 kg, the absolute oxygen uptake is
between about 3,2 l/min and 3,6 l/min. In Reference [21], mean values of (2,4 ± 0,5) l/min for a 17-min
test drill exercise were reported; Reference [16] reported a mean value of (2,75 ± 0,3) l/min for a 22-min
test drill. The average value for the most demanding task (ascending a tower) was (3,55 ± 0,27) l/min.
The range of values for this task was between 3,24 l/min and 4,13 l/min. This corresponded to average
2 2
metabolic rates of 474 W/m and 612 W/m , respectively.
Table 1 — Classification of work based on metabolic rate (MR)
Average metabolic rate
Class Work
2
W/m
1 Resting 65
2 Light work 100
3 Moderate work 165
4 Heavy work 230
5 Very heavy work 290
6 Very, very heavy work (2 h) 400
7 Extremely heavy work (15 min) 475
8 Maximal work (5 min) 600
NOTE The first five classes in this table are derived from ISO 8996. These classes are valid
for repeated activities during work shifts in every day occupational exposure. Classes 6 to 8
are added as examples of metabolic rates associated with temporary activities of an escape
and rescue nature while wearing RPD.
Table 1 of this part of ISO/TS 16976 contains three additional classes compared with ISO 8996:2004,
Table A.2, in order to cover work that is, by its nature, limited by time, such as firefighting and rescue.
One class refers to sustained rescue action, as can be found in mining or in wild land firefighting, with
time periods of up to 2 h of work (class 6). The other two classes refer to firefighting or rescue operations
of short duration and very high intensity, i.e. 15 min (class 7) and 5 min (class 8), respectively. Table 1
presents values expected from individuals with a high level of physical fitness. The highest class
(class 8) represents maximal or close to maximal work and can only be endured by fit men for durations
2 2
of 3 min to 5 min. The three new classes are defined by metabolic rates at 400 W/m , 475 W/m , and
2
600 W/m , respectively. The values represent the average metabolic rate for the specified period of
time, excluding any breaks.
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For natural reasons, many types of rescue and emergency work are carried out with personal protective
equipment. This adds to the physical workload and is one reason for the high values of metabolic rate
in classes 6 to 8. The data given for the types of work shown in classes 1 to 5 are carried out without
wearing RPD and/or personal protective equipment.
5 Metabolic rate and oxygen consumption
The energetic equivalent (EE) of oxygen as described in ISO 8996:2004, 7.1.2, is determined using
Formula (1):
EE=×(,0230RQ+×,)77 58, 8 (1)
where RQ is the respiratory quotient [the ratio of the amount of carbon dioxide produced to the amount
of oxygen consumed (V /V )] and the energetic equivalent of oxygen is 5,88 Wh/l O , which
2
CO O
2 2
corresponds approximately to the value of 5 kcal/l O , a value that is commonly found in the
2
physiological literature.
Assuming a value of 5 kcal/l O (equal to 5,815 Wh/l O ), the following expressions apply for the
2 2
2
conversion of metabolic rates (in W/m ) to V (in l/min):
O
2
MA× MA× MA×
Du Du Du
V = = = (2)
O
2
EE 60×5,815 349
where
is the oxygen consumption, in l/min;
  V
O
2
2
  M is the metabolic rate, in W/m ;
  A is the Dubois body surface area, in m;
Du
  60 is the conversion factor for min/h;
  and the energy equivalent of oxygen is 5,815 Wh/l O .
2
For the same metabolic rate, the oxygen consumption will vary dependant on body size. Examples are
given in Tables 3, 4, and 5 for persons representing three body sizes. The associated body surface area is
2 2 2
1,69 m , 1,84 m , and 2,11 m , respectively. As defined in ISO 8996, a person’s body surface area, A , is
Du
determined on the basis of values for body weight, W , in kg, and body height, H , in m, by Formula (3):
b b
0,,425 0725
AW=×0,202 ×H (3)
Du
bb
Values for V in Tables 3, 4, and 5 are based on Formulae (4), (5), and (6).
O
2
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2
A small-sized person is defined by W = 60 kg, H = 1,7 m, and A = 1,69 m . The oxygen consumption,
b b Du
V , is calculated by Formula (4):
O
2
M
V = (4)
O
2
207
2
A medium-sized person is defined by W = 70 kg, H = 1,75 m, and A = 1,84 m . The oxygen
b b Du
consumption, V , is calculated by Formula (5):
O
2
M
V = (5)
O
2
190
2
A large-sized person is defined by W = 85 kg, H = 1,88 m, and A = 2,11 m . The oxygen consumption,
b b Du
V , is calculated by Formula (6):
O
2
M
V = (6)
O
2
160
6 Oxygen consumption and minute volume
Oxygen transport to tissues requires its extraction from inspired air in the lungs. Concentration of
oxygen in inspired air is equivalent to atmospheric concentration of 20,93 % by volume in dry air.
Normally, only 15 % to 30 % of this fraction is consumed. The expired air still contains approximately
15 % to 18 % O by volume. This means that the minute ventilation of air, V , required for most levels of
2 E
oxygen consumption, is about 20 to 25 times higher (see Reference [3]). At high activity levels, the value
may be even higher, as there is a tendency for hyperventilation.
Reference [9] contains a review of 19 papers published in the relevant literature. The data for 14 non-
respirator studies are plotted again in Figure 1, together with data from References [7], [17], and [18].
Each data point represents the mean value of several individual subjects. The linear regression line for
the mean values is plotted. A power function regression line differs only marginally from the linear
model. The Hagan equation (at the bottom of the graph) provides an exponential regression that
overestimates V at low and very high V levels and underestimates at medium levels. Exponential
E
O
2
relations have also been proposed by others (see References [1] and [12]). All three of the studies
mentioned used incremental exercise as a means of increasing the workload. It can be questioned if V
E
and V equilibrate in such a short time. In particular, V should have a time constant of more than a
O O
2 2
minute. In the Hagan study, workload was increased every minute.
From a physiological point of view, one would not expect an exponential relationship. Indeed, individual
curves show that, up to 60 % to 70 % of maximum V , the relation is almost linear. At higher levels of
O
2
V , hyperventilation increases V in a curvilinear manner (see Reference [3]). Respiratory adaptation
E
O
2
to increased workloads is likely to represent a two-component equation: one linear and one power or
exponential. The model equation would be described by Formula (7):
bx×
ya=×xe+ (7)
()
where
  a, b are constants;
  y represents V ;
E
  x
represents V .
O
2
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At low values of x, the first term is determinant. With increasing x, the second component becomes
more and more important. The highest correlation coefficient is obtained for a = 27,1 and b = 0,839. The
2
value of R = 0,90.
2
Applying a linear regression forced through zero provides a value of R = 0,90. For simplicity, the linear
regression is selected. The regression equation for the mean values is given by Formula (8). Calculating
V for two times the standard error (S ) of the average V , representing 95 % of the populations, gives
E E E
Formula (9). S defines the error in the prediction of V , based on the regression equation, Formula (7).
E E
These equations are subsequently used for estimations of V and peak flows (see Tables 3 to 5).
E
VV=×31,85 (8)
EO
2
VV=×41,48 +2S (9)
()
EO E
2
where
is the mean value of V ;
  V
O
O
2
2
is the standard error.
  S
E
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Y
180
160
1
140
2
120
100
3
80
4
60
40
20
4
Key
X
oxygen consumption, V , in l/min STPD
O
2
Y minute ventilation, V , in l/min BTPS
E
1 y = 41,48 × x
2 y = (27,18 × x) + exp(0,839 × x)
3 y = 31,85 × x
4 Hagen equation
NOTE 1 Each dot represents the average of a sample of subjects exposed to various conditions of work (without
respiratory protective device).
NOTE 2 Data include 14 studies reported in References [9] and [16].
Figure 1 — Relation between minute ventilation, V , and oxygen consumption, V
E
O
2
7 Minute volume and peak inspiratory flow rates
7.1 Normal breathing
During the respiratory cycle, the inspired (and expired) volume and its flow rate changes with time. A
simple description of the respiratory cycle can be described by a sinus curve.
The mean flow rate during an inhalation is the inspired volume (tidal volume) divided by the time. The
minute ventilation is the total volume of air exchanged in the lungs during 1 min.
The instantaneous flow rate during the respiratory cycle is described by the derivative of the volume
curve, which is in fact a sinus curve. Peak inspiratory flow rate (PIFR) is mathematically defined by
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the minute ventilation multiplied by π, if the respiratory pattern follows a sinus curve. PIFR occurs for
fractions of a second within the inhalation cycle and is best expressed in l/s.
As ventilation increases in response to increasing workload, the breathing pattern transforms from
a predominantly sinusoidal to a trapezoidal pattern, indicating that flow rates and in particular peak
flow rates may be different than for the sinus cycle (see Reference [20]). It was concluded that peak
inspiratory flow rates were 2,5 to 3,7 times as high as the mean minute volumes. The highest ratio was
achieved at rest and reduced with exercise intensity. During work, the ratio was lower and relatively
constant, independent of workload. At maximal voluntary hyperventilation, the peak values were 2,5
times as high as the mean minute volume values.
Similar results were reported in Reference [28], which re-analysed data reported in Reference [29].
The ratio for peak flows and mean minute ventilation was also calculated, with the ranges found to be
from 2,5 to 3,9.
Reference [21] provides an analysis of several independent sets of data for PIFR/V . The data (see
E
2
Figure 2) were well correlated (R = 0,986 7) and fitted Formula (10):
PIFR =×2,,346 V +20 828 (10)
()
E
In Reference [7], PIFR during incremental bicycle exercise, breathing through several types of negative
pressure filtering devices, is reported. Similar data have been obtained in Reference [18]. The relation
between PIFR and V is shown in Figure 3. The data in Reference [9] have been converted and are
E
included in Figure 3 a). There is a tendency for higher ratio at low minute volumes.
7.2 Speech and breathing
Several investigators report that speech during use of respiratory protective devices changes the
respiratory dynamics. Speech is performed during the expiration phase of the breathing cycle. This
shortens the inspiration phase accordingly and it may become critically short during very high activity
levels (see References [10], [18] and [30]). This shortening of the inspiratory phase suggests that speech
becomes very difficult at very high activity levels.
Minute ventilation during speech is related almost linearly to minute ventilation without speech.
In Reference [7], a regression line of V = 0,83 × V is reported. Similarly, a regression line of
E,speech E
V = 0,78 × V is reported in Reference [18]. It can be assumed that V during speech reduces by
E,speech E E
about 20 % compared with V in no speech conditions. The reduction appears to be similar, independent
E
of work rate. Accordingly, the following relation is applied:
VV=×08, (11)
E,speechE
With shorter inspiration time, the peak flow rates are reported to increase even more than during a
normal breath. Peak inspiratory flow rates about six times higher than the mean minute ventilation
have been reported (see References [7] and [18]).
In References [7] and [18], PIFR was investigated during work sessions with standardized speech
communication. Results are given in Figure 3 b). In Reference [7], incremental bicycle exercise was used,
whereas in Reference [18], treadmill walking with incremental increases in slope was used. Results for
the PIFR/V ratio are in good agreement. It is apparent that the ratio is high at low minute volumes, but
E
that it approaches the “no speech” values at high minute volumes. The power function regression line
shows a high correlation factor. It is apparent from these data that speech is not a significant contributor
to PIFR at extremely heavy work, most probably because it is difficult to sustain continuous speech, but
it is still possible to say single words at very high ventilation rates.
Formulae (12) and (13) apply to the calculation of PIFR from V .
E
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For no speech:
−0,167 5 0,832 5
PIFR =5,605××VV =5,605×fV or no speech (12)
E EE
For speech:
−0,474 3 0,5255 7
PIFR =36,707×(0,8×VV)×(0,8×)=36,707×(0,8×V ) for speech (13)
E EE
Y
300
250
200
150
100
50
Key
X minute ventilation, V , in l/min BTPS
E
Y peak inspiratory flow, in l/min
NOTE For details, see Reference [21].
Figure 2 — Relation between peak inspiratory flow rate and minute ventilation
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Y
a) Relation for no speech conditions
Y
b) Relation measured when subjects read a standard text during exercise
Key
X minute ventilation, V , in l/min BTPS
E
Y ratio PIFR/V
E
NOTE 1 Figure 3 a) is based on mean values for 37 conditions in four independent studies.
NOTE 2 In Figure 3 b), the data report mean values from 13 conditions in two independent studies.
Figure 3 — Ratio of peak inspiratory flow rate to minute ventilation as a function of minute
ventilation during work using negative pressure (filter) breathing apparatus
7.3 Sneezing and coughing
7.3.1 General
During use of respiratory devices, it may happen that wearers will sneeze or cough, which has a different
aerodynamic effect from a typical breathing pattern. A number of studies have been performed which
give measurements of effects of these phenomena.
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7.3.2 Maximum pressures
7.3.2.1 Maximum expiratory pressures
In Reference [10], the reported maximum expiratory pressures were 14,9 (SD = 3,5) kPa in women, 24,2
(SD = 4,6) kPa in 29-year-old men, and 15,6 (SD = 6,4) kPa in 59-year-old men. In Reference [23], the
measured maximum expiratory pressures were (13 ± 2,6) kPa in men and (10 ± 1,8) kPa in
...