EN ISO 16972:2020

SLOVENSKI STANDARD
01-junij-2020
Nadomešča:
SIST EN 132:1999
Oprema za varovanje dihal - Slovar in grafični simboli (ISO 16972:2020)
Respiratory protective devices - Vocabulary and graphical symbols (ISO 16972:2020)
Atemschutzgeräte - Begriffe und graphische Symbole (ISO 16972:2020)
Appareils de protection respiratoire - Vocabulaire et symboles graphiques (ISO
16972:2020)
Ta slovenski standard je istoveten z: EN ISO 16972:2020
ICS:
01.040.13 Okolje. Varovanje zdravja. Environment. Health
Varnost (Slovarji) protection. Safety
(Vocabularies)
13.340.30 Varovalne dihalne naprave Respiratory protective
devices
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 16972
EUROPEAN STANDARD
NORME EUROPÉENNE
March 2020
EUROPÄISCHE NORM
ICS 01.040.13; 13.340.30
English Version
Respiratory protective devices - Vocabulary and graphical
symbols(ISO 16972:2020)
Appareils de protection respiratoire - Vocabulaire et Atemschutzgeräte - Begriffe und graphische Symbole
symboles graphiques (ISO 16972:2020) (ISO 16972:2020)
This European Standard was approved by CEN on 23 February 2020.

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 CEN-CENELEC 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 CEN-CENELEC Management
Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2020 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 16972:2020 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
This document (EN ISO 16972:2020) has been prepared by Technical Committee ISO/TC 94 "Personal
safety -- Personal protective equipment" in collaboration with Technical Committee CEN/TC 79
“Respiratory protective devices” 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 September 2020, and conflicting national standards
shall be withdrawn at the latest by September 2020.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN 132:1998.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the
United Kingdom.
Endorsement notice
The text of ISO 16972:2020 has been approved by CEN as EN ISO 16972:2020 without any modification.

INTERNATIONAL ISO
STANDARD 16972
Second edition
2020-03
Respiratory protective devices —
Vocabulary and graphical symbols
Appareils de protection respiratoire — Vocabulaire et symboles
graphiques
Reference number
ISO 16972:2020(E)
©
ISO 2020
ISO 16972:2020(E)
© ISO 2020
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting
on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address
below or ISO’s member body in the country of the requester.
ISO copyright office
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CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Fax: +41 22 749 09 47
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2020 – All rights reserved

ISO 16972:2020(E)
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms related to respiratory protective devices . 1
4 Terms related to human factors .25
5 Graphical symbols for use on respiratory protective devices .31
Bibliography .32
Index .33
ISO 16972:2020(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 of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see www .iso .org/
iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 94, Personal safety — Personal protective
equipment, Subcommittee SC 15, Respiratory protective devices, in collaboration with the European
Committee for Standardization (CEN) Technical Committee CEN/TC 79, Respiratory protective devices,
in accordance with the Agreement on technical cooperation between ISO and CEN (Vienna Agreement).
This second edition cancels and replaces the first edition (ISO 16972:2010), which has been technically
revised. The main changes compared with the previous edition are as follows:
— the terms used in the field of respiratory protective devices (RPD) have been updated;
— Clause 5, “Units of measurement”, has been deleted;
— Annex A, “Terms and definitions referring to respiratory protective devices in current national
standards, regulations or other national contexts”, has been deleted;
— Annex B, “Abbreviations used”, has been deleted.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/ members .html.
iv © ISO 2020 – All rights reserved

INTERNATIONAL STANDARD ISO 16972:2020(E)
Respiratory protective devices — Vocabulary and
graphical symbols
1 Scope
This document defines terms and specifies units of measurement for respiratory protective devices
(RPDs), excluding diving apparatus. It indicates graphical symbols that can be required on RPDs, parts
of RPD or instruction manuals in order to instruct the person(s) using the RPD as to its operation.
NOTE Terms and definitions for diving apparatus are given in EN 250.
2 Normative references
There are no normative references in this document.
3 Terms related to respiratory protective devices
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
abrasive blasting respiratory protective device
breathing apparatus (3.32) incorporating a protective hood (3.115) or a blouse (3.23) fitted with an
impact resistant (3.119) visor (3.252)
Note 1 to entry: Breathable air (3.28) is supplied to the wearer (3.257) from a source of air not carried by the wearer.
3.2
accessory
item, or items, that are attached to the respiratory protective device (RPD) (3.203) that are not necessary
for the RPD to meet the requirements of the RPD performance standard and do not compromise its
protection
3.3
adequacy assessment
selection method identifying the respiratory protective device (3.203) is able to reduce the wearer's
(3.257) inhalation exposure to acceptable levels
3.4
adequate respiratory protective device
adequate RPD
RPD (3.203) capable of reducing the inhalation exposure to an acceptable level
3.5
aerodynamic diameter
diameter of a unit density sphere having the same settling velocity as the particle (3.170) in question
3.6
aerosol
suspension of solid, liquid, or solid and liquid particles (3.170) in a gaseous medium, having a negligible
falling velocity (generally considered to be less than 0,25 m/s)
ISO 16972:2020(E)
3.7
aerosol penetration
ability of particles (3.170) to pass through a particle-filtering material
3.8
air flow resistance
pressure difference between upstream and downstream locations caused by the flow of air through
the parts and components of a respiratory protective device (3.203) such as an exhalation valve (3.79),
inhalation valve (3.120), filter(s) (3.86), and tube (3.245), etc.
3.9
air supply hose
fresh air supply hose
hose (3.116) for the supply of air at about atmospheric pressure
3.10
ambient air bypass
means to enable the wearer (3.257) to breathe the ambient atmosphere (3.12) before entering and after
leaving a hazardous atmosphere (3.108)
3.11
ambient air system
device used to deliver ambient air at a low pressure (3.134) directly to a breathable gas (3.29) respiratory
protective device (3.203) (manually or power assisted)
3.12
ambient atmosphere
air surrounding the wearer (3.257)
3.13
ambient concentration
concentration of a compound in the air surrounding the wearer (3.257)
3.14
ambient laboratory conditions
atmosphere where the temperature is between 16 °C and 32 °C and the relative humidity is between
20 % and 80 %
3.15
apertometer
extended hemispherical dome for measuring the angular area of the field of vision (3.85) [peripheral
isopter (3.176)] of a respiratory protective device (3.203) when mounted on a respiratory protective
device headform (3.204)
3.16
as received
not preconditioned or modified to carry out a test
3.17
assigned protection factor
APF
anticipated level of respiratory protection that would be provided by a properly functioning respiratory
protective device (RPD) (3.203) or class of RPD within an effective RPD programme (3.207)
3.18
assisted filtering respiratory protective device
assisted filtering RPD
filtering RPD (3.90) where breathable gas (3.29) is actively supplied to the wearer (3.257) by the
RPD (3.203)
2 © ISO 2020 – All rights reserved

ISO 16972:2020(E)
3.19
averaged interactive flow rate
interactive flow rate (3.126) averaged over 10 consecutive breathing cycles (3.34) of the breathing
machine (3.38)
3.20
averaged maximum interactive flow rate
average of the highest flow rate (3.92) within each breathing cycle (3.34) of 10 consecutive breathing
cycles of the breathing machine (3.38)
3.21
averaged minimum interactive flow rate
average of the lowest flow rate (3.92) within each breathing cycle (3.34) of 10 consecutive breathing
cycles of the breathing machine (3.38)
3.22
averaged peak interactive flow rate
average of the maximum peak flow rate (3.92) within each breathing cycle (3.34) of 10 consecutive
breathing cycles of the breathing machine (3.38)
3.23
blouse
garment, used as a facepiece (3.83), that covers the head and upper part of the body to the waist and
wrists and to which air is supplied
3.24
body harness
means to enable certain components of a respiratory protective device (3.203) to be worn on the body
3.25
body temperature pressure saturated
BTPS
standard condition for the expression of ventilation (4.20) parameters
Note 1 to entry: Body temperature (37 °C), atmospheric pressure 101,3 kPa and water vapour pressure (6,27 kPa)
in saturated air.
3.26
breakthrough concentration
concentration of test gas (3.97) in effluent air at which a gas filter (3.98) undergoing a gas capacity
(3.44) test is deemed exhausted
3.27
breakthrough time
t
br
time taken from the start of the test until the test gas (3.97) and specified reaction products are
detected at the specified breakthrough concentration (3.26) at the downstream side of the filter (3.86)
under test
3.28
breathable air
air of a quality that makes it suitable for safe respiration
Note 1 to entry: For compressed air for breathing apparatus (3.32), see EN 12021:2014.
3.29
breathable gas
mixture of gases (3.97) that is suitable for respiration without adverse effects to health
ISO 16972:2020(E)
3.30
breathable gas cylinder
integral part of the respiratory protective device (3.203) that contains the breathable gas (3.29) supply
3.31
breathable gas quality
composition of a breathable gas (3.29) as defined in relevant standards
3.32
breathing apparatus
device that enables the wearer (3.257) to breathe independently of the ambient atmosphere (3.12)
3.33
breathing bag
component of a respiratory protective device (3.203) that compensates for variations in the breathable
gas (3.29) supply or demand and provides for peak inhalation flow requirements
3.34
breathing cycle
respiratory period comprising an inhalation and an exhalation phase
3.35
breathing frequency
number of breathing cycles (3.34) taken in a minute
Note 1 to entry: It is expressed in breaths per minute.
3.36
breathing gas regeneration
process whereby a respiratory protective device (3.203) absorbs carbon dioxide from exhaled gas (3.97),
delivers oxygen, and controls the water vapour and temperature of gas to be rebreathed
3.37
breathing hose
flexible hose (3.116) connected to the facepiece (3.83) through which breathable gas
(3.29) enters at atmospheric pressure or at a pressure slightly above or below
3.38
breathing machine
ventilation machine that simulates respiratory ventilation (4.20) using waveforms, which can be
sinusoidal or representative of the breathing cycle (3.34)
Note 1 to entry: See also metabolic simulator (3.149).
3.39
breathing machine assembly
breathing machine (3.38) plus all the connecting tubes (3.245), control valves and other necessary
hardware leading to the trachea tube assembly (3.244)
3.40
breathing peak resistance
maximum differential pressure of a respiratory protective device (3.203) during inhalation (inhalation
peak resistance) or exhalation (exhalation peak resistance)
3.41
breathing resistance
pressure differential between the upstream and downstream location caused by a respiratory
protective device (3.203) to the flow of breathable gas (3.29) during inhalation (inhalation resistance) or
exhalation (exhalation resistance)
4 © ISO 2020 – All rights reserved

ISO 16972:2020(E)
3.42
breath-responsive
actively or passively responsive following the wearer's (3.257) demand for air
3.43
bypass valve
component part of a respiratory protective device (3.203) that is furnished as an emergency manual
valve to supply necessary breathable gas (3.29) when the ordinary supply path is out of order
3.44
capacity
volume of available breathable gas (3.29) of a respiratory protective device (3.203)
3.45
carbon dioxide concentration limits
CO concentration limits
maximum allowed concentration of carbon dioxide within inhaled breathable gas (3.121)
3.46
char length
length of brittle residue found when a fabric or material is exposed to thermal energy
3.47
checking device
means to enable the wearer (3.257) to verify, before use or periodically during use, that the
manufacturer’s minimum design conditions (3.137) are met
3.48
class Sxxxx respiratory protective device
class Sxxxx RPD
supplied breathable gas RPD (3.236), where Sxxxx equals the amount of breathable gas (3.29) available
for respiration in litres
3.49
cleaning/disinfection resistance
ability of the device to withstand the cleaning and disinfection processes defined by the manufacturer
3.50
combined filter
filter (3.86) intended to remove dispersed solid and/or liquid particles (3.170) and specified gases (3.97)
and vapours (3.251) from the flow of air passing through it
3.51
combined respiratory protective device
combined RPD
RPD (3.203) that is capable of operating in either a filtering or breathable gas (3.29) supply mode
3.52
compatibility
ability of a respiratory protective device (3.203) to be used in conjunction with another item of personal
protective equipment (PPE)
3.53
competent fit-test operator
person with suitable and sufficient experience and with practical and theoretical knowledge of fit-test
methods who conducts the fit-testing procedures
3.54
competent person
person with suitable and sufficient experience and with practical and theoretical knowledge of the
elements of a respiratory protective device programme (3.207) for which (s)he is responsible
ISO 16972:2020(E)
3.55
compressed air filter
filter (3.86) intended to remove dispersed solid and/or liquid particles (3.170) and specified gases (3.97)
and vapours (3.251) from compressed air passing through it
3.56
compressed air line breathing apparatus
device that is not self-contained and in which the facepiece (3.83) is supplied with breathable air (3.28)
from a source of compressed air
3.57
compressed air supply tube
tube (3.245) that delivers breathable air (3.28) at a maximum pressure of 10 bar from a source of
compressed air
3.58
confined space
area with limited access, as described in national regulations, which requires special considerations
for entry
3.59
contaminant
undesirable solid, liquid or gaseous substance in the air
3.60
continuous control flow valve
control valve that provides the wearer (3.257) of a supplied breathable gas respiratory protective device
(3.236) with breathable gas (3.29) and allows the wearer to regulate a continuous air flow within
prescribed limits
3.61
count median diameter
CMD
particle size of a particle distribution for which one-half the total number of particles (3.170) are larger
and one-half are smaller
3.62
dead space
space in which exhaled gas (3.97) has not been purged and is subject to being rebreathed
3.63
dead space
conducting regions of the pulmonary airways that do not contain alveoli (4.7) and,
therefore, where no gas (3.97) exchange occurs
Note 1 to entry: These areas include the nose, mouth, trachea, large bronchia and the lower branching airways.
This volume is typically 150 ml in a male of average size.
3.64
dead space
sum of all anatomical dead space (3.63) as well as under-perfused (reduced blood flow)
alveoli (4.7) that are not participating in gas (3.97) exchange
Note 1 to entry: The volume of the physiological dead space can vary with the degree of ventilation (4.20). Thus,
the physiological dead space is the fraction of the tidal volume (3.240) that does not participate in gas exchange
in the lungs.
6 © ISO 2020 – All rights reserved

ISO 16972:2020(E)
3.65
demand type with positive pressure
type of respiratory protective device (3.203) that is fitted with a demand valve (3.67), is governed by
the breathing action of the lungs, and that actuates at a positive pressure (3.179) in the facepiece (3.83)
under conditions defined in relevant standards
3.66
demand type without positive pressure
type of respiratory protective device (3.203) that is fitted with a demand valve (3.67), is governed by the
breathing action of the lungs, and that actuates at a negative pressure (3.161) during inhalation in the
facepiece (3.83)
3.67
demand valve
valve that is governed by the breathing action of lungs and that supplies breathable gas (3.29) on demand
3.68
desorption
process in which one substance (the filter medium) releases an absorbed or adsorbed substance
3.69
dew point
temperature of air at a specified pressure below which condensation will occur
3.70
doffing
process of removing or taking off the respiratory protective device (3.203)
3.71
donning
process of putting on the respiratory protective device (3.203)
3.72
downstream valve
valve that opens with the pressure of the air and is normally kept shut by means of a spring
3.73
drip
to run or fall in drops or blobs
3.74
dynamic breathing resistance
differential pressure caused by a respiratory protective device (3.203) when the breathable gas (3.29)
is delivered by a breathing machine (3.38) adjusted to a specified breathing minute volume (3.153) and
waveform
3.75
dynamic flame test
test where the specimen is moving over the flame for the exposure
3.76
elastance
E
pressure change resulting from a volume change
Note 1 to entry: It is expressed in kPa/l.
ISO 16972:2020(E)
3.77
end-of-service-life indicator
ESLI
system that warns the wearer (3.257) of the gas filtering respiratory protective device (3.102) of the
approach of the end of respiratory protection
3.78
escape respiratory protective device
escape RPD
RPD (3.203) designed to be used only during an escape from hazardous atmospheres (3.108)
3.79
exhalation valve
non-return valve that allows the release of exhaled and excess breathable gas (3.29) from the respiratory
protective device (3.203)
3.80
exhaled air
air breathed out by the wearer (3.257)
3.81
exposed part
part that can be touched in an as-worn state by the exposed surface identification probe specified in
ISO 16900-5
3.82
face blank
main body of a facepiece (3.83) to which the functional components are attached
3.83
facepiece
part of a respiratory protective device (3.203) that connects the wearer's (3.257) respiratory tract to the
other parts of the device and isolates the respiratory tract from ambient atmosphere (3.12)
Note 1 to entry: Facepieces may be full face masks (3.96), half masks (3.104), quarter masks (3.192), mouthpiece
assemblies (3.157) or filtering facepieces (3.89).
Note 2 to entry: Helmets (3.113), hoods (3.115), blouses (3.23) and suits may serve the same purpose.
3.84
face-seal leakage
leakage between the wearer's (3.257) face and the respiratory interface (3.202)
3.85
field of vision
area of fixed sight while wearing a respiratory protective device (3.203)
3.86
filter
device intended to remove specific contaminants (3.59) from the ambient air passing through it
3.87
filter holder
filter housing
component that is attached to either a respiratory interface (3.202) or another part of the respiratory
protective device (3.203) and into which a filter (3.86), either encapsulated or un-encapsulated, is
inserted
8 © ISO 2020 – All rights reserved

ISO 16972:2020(E)
3.88
filter self rescuer
respiratory protective device (3.203) exclusively intended for escape, incorporating a filter (3.86) against
carbon monoxide through which the ambient air is drawn to a facepiece (3.83)
3.89
filtering facepiece
respiratory protective device (3.203) entirely or substantially constructed of filtering material
Note 1 to entry: Marked "FF" for filtering facepiece.
3.90
filtering respiratory protective device
filtering RPD
assisted or unassisted RPD (3.203) in which air passes through a gas filter(s) (3.98), particle filter(s)
(3.171) or combined filter(s) (3.50) before being inhaled
3.91
fit test
use of a challenge agent and specific protocol to qualitatively or quantitatively determine the
effectiveness of the seal between the wearer's (3.257) face and respiratory interface (3.202) with a
specific make, model and size of a respiratory protective device (3.203)
3.92
flow rate
V
fl
volume (mass) of breathable gas (3.29) passing through the device in a given time
3.93
fogging
reduction of the field of vision (3.85) and/or visual acuity caused by the condensation of humidity on the
visor (3.252)
3.94
force-fitting
practice of repeating a failed fit test (3.91) with the same respiratory protective device (RPD) (3.203)
more than three times, re-donning, or otherwise adjusting the RPD (e.g. over-tightening the straps),
until a passing fit test is finally achieved
3.95
fresh air hose breathing apparatus
respiratory protective device (3.203) in which breathable air (3.28) is obtained through an air supply
hose (3.9) either assisted or unassisted
3.96
full face mask
tight-fitting respiratory interface (3.241) covering the mouth, nose, eyes and chin
3.97
gas
fluid that is in a gaseous state at a standard temperature and pressure that expands to occupy the space
or enclosure in which it is confined
3.98
gas filter
filter (3.86) intended to remove specific gases (3.97) and vapours (3.251) from the atmosphere passing
through it
ISO 16972:2020(E)
3.99
gas filter capacity
mass or volume of a specific test agent that is removed or retained by a gas filter (3.98) or combined
filter (3.50) under specified conditions of temperature, humidity, challenge test gas concentration and
flow rate (3.92) at breakthrough concentration (3.26)
Note 1 to entry: The mass or volume is determined by measuring the breakthrough time (3.27) at a defined
breakthrough concentration. The formula to calculate the gas capacity (3.44) is:
−6
CV=×ct××10
fl gasbr
where
C is gas capacity (in l);
V is volume flow rate (3.92) (in l/min);
fl
c is gas concentration (in ml/m );
gas
t is breakthrough time (3.27) (in min).
br
EXAMPLE V = 30 l/min
fl
c = 1 000 ml/m
gas
t = 30 min
br
3 −6
C = 30 l/min × 1 000 ml/m × 30 min × 10 = 0,9 l
3.100
gas filter change schedule
time interval after which a gas filter (3.98) is replaced with a new one
3.101
gas filter validation test at specified flow rates
test to evaluate the ability of the filter (3.86) to achieve a minimum performance level at its work rate
(3.260) classification
3.102
gas filtering respiratory protective device
gas filtering RPD
RPD (3.203) consisting of a respiratory interface (3.202) with a filter (3.86) that removes certain gases
(3.97) or vapours (3.251) from the air to be inhaled by the wearer (3.257) for a limited period
3.103
hairnet
head net
head harness (3.110) in the form of a net (mesh fabric)
3.104
half mask
tight-fitting respiratory interface (3.241) covering the mouth, nose and chin
3.105
half mask without inhalation valves
filtering device with a half mask (3.104) and without inhalation valves (3.120), which may or may not
have exhalation valves (3.79)
Note 1 to entry: It comprises a half mask and separable and replaceable filters (3.86).
10 © ISO 2020 – All rights reserved

ISO 16972:2020(E)
3.106
hand wheel diameter
D
nominal value of twice the largest radius from the centre of the hand wheel
Note 1 to entry: It is expressed in mm.
3.107
hazard ratio
measured airborne concentration of a substance divided by the occupational exposure limit (3.163)
Note 1 to entry: This ratio is calculated for each gas (3.97), vapour (3.251) and/or particulate component, or for a
mixture when the components have additive effects.
3.108
hazardous atmosphere
any atmosphere that is oxygen-deficient and/or where the level of substances in the atmosphere is at a
concentration deemed to be hazardous
3.109
hazardous substance
substance that presents a potential to cause injury or ill health if it is inhaled, ingested or comes into
contact with, or is absorbed through, the skin
Note 1 to entry: A hazardous substance may be a pure substance or generated as a by-product during work
activities. For example, wood dust and stone dust welding fume.
Note 2 to entry: Hazardous substances can be present in the atmosphere in a number of physical states as:
a) gases (3.97);
b) vapours (3.251);
c) particles (3.170).
3.110
head harness
means of holding a respiratory interface (3.202) in place on the head
3.111
heads up display
HUD
visual monitor (3.155) or warning in the line of sight of the wearer (3.257)
3.112
heavy duty construction
mechanical properties of a respiratory protective device (3.203) designed to be used in work situations
with need for a mechanically robust device
Note 1 to entry: See also light duty construction (3.131).
3.113
helmet
respiratory interface (3.202) offering head protection
3.114
high pressure
pressure equal to or greater than 2 MPa absolute pressure
3.115
hood
loose-fitting respiratory interface (3.132) that covers at least the face and can cover the entire head
ISO 16972:2020(E)
3.116
hose
hollow flexible conduit to transport breathable gas (3.29)
3.117
hydrostatic test
calibrated expansion pressure test of the structural integrity of cylinders
3.118
immediately dangerous to life or health
IDLH
atmosphere that poses an immediate threat to life, would cause irreversible adverse health effects, or
would impair an individual’s ability to escape from a hazardous atmosphere (3.108)
3.119
impact resistance
ability of a respiratory protective device (3.203) to withstand mechanical shock and dynamic stress
from the environment
3.120
inhalation valve
valve that opens during inhalation and closes during exhalation
3.121
inhaled breathable gas
breathable gas (3.29) breathed in by the wearer (3.257)
3.122
inspection
process that assesses the respiratory protective device (RPD) (3.203), components, marking (3.139),
information supplied by the RPD manufacturer (3.206) and any safety data sheets (if applicable) or
declarations relevant to the materials used in its construction
3.123
integral dose
volume of the test gas (3.97) on the effluent side of the filter (3.86) released during the testing period
Note 1 to entry: This is calculated as the integral of the instant effluent concentration (function of time) of the
test gas during the testing time multiplied by the volume flow rate (3.92).
3.124
integral filter
filter (3.86) that is not separable from the rest of the respiratory interface (3.202)
3.125
interactive flow
flow resulting from the combined action of a power-assisted device and a tidal breathing pattern at the
respiratory interface (3.202)
3.126
interactive flow rate
flow rate (3.92) through the filters (3.86) of an assisted filtering respiratory protective device (RPD) (3.18)
resulting from the combined action of the assisted filtering RPD and the breathing pattern generated
by the breathing machine (3.38)
3.127
intrinsic safety
(type of) protection where the respiratory protective device (3.203) is not a source of ignition in
explosive atmospheres
12 © ISO 2020 – All rights reserved

ISO 16972:2020(E)
3.128
inward leakage
leakage of the ambient atmosphere (3.12) into the respiratory interface (3.202) from all sources excluding
the filter(s) (3.86), where present, when measured in the laboratory in the specific test atmosphere
Note 1 to entry: It is expressed as a percentage ratio of contaminant (3.59) concentration inside a respiratory
protective device (3.203) and ambient atmosphere.
3.129
leak-tightness
ability to withstand a loss of pressure inside a respiratory protective device (3.203) over a given time as
determined by a laboratory test
3.130
life cycle
time between the date of manufacturing of the device to the date when the device has to be withdrawn
from service
3.131
light duty construction
mechanical properties of a respiratory protective device (3.203) designed to be used in work situations
with little risk of mechanical damage
Note 1 to entry: See also heavy duty construction (3.112).
3.132
loose-fitting respiratory interface
loose-fitting RI
RI (3.202) that does not rely on forming a complete seal to the wearer's (3.257) skin
3.133
low boiling organic compound
organic compound having a boiling point of ≤ 65 °C at atmospheric pressure
3.134
low pressure
pressure up to 100 hPa above atmospheric pressure
3.135
lung governed demand valve
valve for breathing apparatus (3.32) by which an air supply is regulated in accordance with the wearer's
(3.257) breathing
3.136
manufacturer's design duration
time, as stated by the manufacturer, for which the manufacturer's minimum design flow rate (3.138) is
exceeded
3.137
manufacturer's minimum design condition
lowest level of operating conditions of the device, as stated by the manufacturer, at which the complete
respiratory protective device (3.203) will still meet the requirements for the designated class
3.138
manufacturer's minimum design flow rate
minimum air flow rate (3.92), as stated by the manufacturer, at which the class requirements are met
3.139
marking
information included on the device to indicate specific respiratory protective device (3.203)
characteristics
ISO 16972:2020(E)
3.140
mass median aerodynamic diameter
MMAD
point in an aerodynamic particle size distribution where half of the mass lies in particles (3.170) with a
diameter less than the MMAD and half in particles with a diameter greater than the MMAD
3.141
maximum flow condition
factors appropriate to the design specified by the manufacturer that give rise to the highest flow
rate (3.92)
3.142
maximum use concentration
MUC
maximum atmospheric concentration of a hazardous substance (3.109) from which the wearer (3.257)
can be expected to be protected when wearing a respiratory protective device (RPD) (3.203)
Note 1 to entry: This is determined by the assigned protection factor (3.17) of the RPD or class of RPD and the
occupational exposure limit (3.163) of the hazardous substance.
Note 2 to entry: The MUC can usually be determined mathematically by multiplying the assigned protection
factor specified for an RPD by the occupational exposure limit used for the hazardous substance.
3.143
measured maximum flow rate
volumetric flow rate (3.92) of an assisted filtering respiratory protective device (RPD) (3.18), determined
in a laboratory test, when the RPD (3.203) is in the condition that results in the highest air flow rate
Note 1 to entry: This condition takes into account the influence of temperatures, settings of RPD, pre-
conditionings, use of accessories and others.
3.144
measured minimum flow rate
volumetric flow rate (3.92) of an assisted filtering respiratory protective device (RPD) (3.18), determined
in a laboratory test, when the RPD (3.203) is in the condition that results in the lowest air flow rate
Note 1 to entry: This condition takes into account the influence of temperatures, settings of RPD, pre-
conditionings, use of accessories and others.
3.145
mechanical strength of the visor
ability of the device to withstand mechanical stress (3.146) to the visor (3.252)
3.146
mechanical stress
dynamic force on the device during a fall from a given height as determined by a laboratory test
3.147
medium pressure
pressure between 100 hPa to 2 MPa above atmospheric pressure
3.148
medium pressure connecting tube
tube (3.245) connecting the demand valve (3.67) or the control valve with the air supply system at a
medium pressure (3.147)
3.149
metabolic simulator
programmable automatic breathing machine (3.38) that can simulate the characteristics of both human
breathing [variable tidal volume (3.240) and respiratory rate, humidity and temperature] and metabolic
functions [variable oxygen consumption (4.5) and carbon dioxide production]
14 © ISO 2020 – All rights reserved

ISO 16972:2020(E)
3.150
metabolic simulator assembly
metabolic simulator (3.149) plus all the connecting tubes (3.245), control valves and other necessary
hardware leading to the trachea tube assembly (3.244)
3.151
minimum flow condition
factors appropriate to the design specified by the manufacturer that give rise to the lowest flow rate (3.92)
3.152
minute ventilation
V
E
total volume of air inhaled (or exhaled) in the lungs during 1 min
Note 1 to entry: It is expressed in l/s body temperature pressure saturated (BTPS) (3.25).
3.153
minute volume
volume of breathable gas (3.29) exhaled in 1 min
3.154
mode of operation
primary means of supplying the wearer (3.257) with breathable gas (3.29), i.e. particle filtering, gas and
vapour filtering, or breathable-gas supplying
3.155
monitor
component of a respiratory protective device (3.203) to enable the wearer (3.257) to continuously
assess that the manufacturer’s minimum design air flow rate (3.92) or manufacturer’s minimum design
conditions (3.137) are met
3.156
mounting flange
device to fix tightly together a full face mask (3.96) and a helmet (3.113)
3.157
mouthpiece assembly
respiratory interface (3.202) held by the teeth or by the teeth and a head harness (3.110), sealing against
the lips and through which air is inhaled and exhaled while the nose is closed by a clip
3.158
multi-functional respiratory protective device
multi-functional RPD
RPD (3.203) that is capable of operating within its mode of operation (3.154) using different operating
methods, for example:
— assisted filtering RPD (3.18);
— power on/off;
— compressed breathable gas (3.29) system with compressed breathable gas RPD
3.159
multiple filters
construction where the full air flow for a respiratory protective device (3.203) is divided between two or
more filters (3.86)
3.160
multi-type gas filter
gas filter (3.98) that meets the requirements of more than one type of gas filter
ISO 16972:2020(E)
3.161
negative pressure
pressure inside the respiratory interface (3.202), hose (3.116), etc. that is lower than that of the ambient
atmosphere (3.12)
3.162
nominal working duration
rated working duration
working time of a device, used for the classification determined in laboratory tests with a specified flow
rate (3.92)
Note 1 to entry: The nominal or rated working duration does not give an indication of the possible effective
working duration of a device in practical use. Possible effective working durations can differ from the nominal or
rated working duration in both directions, positive and negative, depending upon the actual work rate (3.260).
3.163
occupational exposure limit
OEL
maximum concentration of airborne contaminants (3.59) deemed to be acceptable, as defined by the
authority having jurisdiction
3.164
open-circuit
technical solution where the exhaled air (3.80) passes without recirculation into the ambient
atmosphere (3.12)
3.165
operating pressure
pressure developed within the respiratory protective device (3.203) during service
3.166
overflow valve
non-return valve, fitted to the breathing hose (3.37), that is specially designed to allow the excess air
supply to escape into the atmosphere
3.167
oxygen compatibility
capability of a respiratory protective device (3.203) to allow direct contact with pressurised oxygen
without risk of fire or explosion by being oil and grease free
3.168
oxygen deficiency
condition based on an oxygen concentration or partial pressure (4.17) below which a person can be
adversely affected
Note 1 to entry: Each authority having jurisdiction may establish an alternative definition or specific limit.
3.169
oxygen-enriched breathable gas
breathable gas (3.29) containing oxygen at a higher concentration than that of atmospheric air at sea level
3.170
particle
solid or liquid substance in the finely divided state
3.171
particle filter
filter (3.86) that is intended to remove airborne particles (3.170)
16 © ISO 2020 – All rights reserved

ISO 16972:2020(E)
3.172
particle filter efficiency
degree to which a filter (3.86) removes aerosols (3.6) from the ambient atmosphere (3.12)
3.173
particle filter respiratory protective devi
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