Mining -- Air quality control systems for operator enclosures -- Performance requirements and test methods

This document specifies performance and design requirements for air quality control systems for operator enclosures and their monitoring devices. The design specifications are universal in their application and do not contemplate specific mining environments. They are intended to meet identified parameters of both pressurization and respirable particulate and carbon dioxide concentrations. This document also specifies test methods to assess such parameters and provides operational and maintenance instructions. Recommendations are made for operational integration of the air quality control system. Gases and vapours that can be a hazard in the work environment outside of the operator enclosure are excluded from this document.

Exploitation minière - Systèmes de contrôle de la qualité de l'air des enceintes de l'opérateur - Exigences de performance et méthodes essai

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INTERNATIONAL ISO
STANDARD 23875
First edition
2021-02
Mining — Air quality control
systems for operator enclosures —
Performance requirements and test
methods
Reference number
ISO 23875:2021(E)
ISO 2021
---------------------- Page: 1 ----------------------
ISO 23875:2021(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2021

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
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2021 – All rights reserved
---------------------- Page: 2 ----------------------
ISO 23875:2021(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

3.1 Terms related to air quality .......................................................................................................................................................... 2

3.2 Terms related to the operator enclosure design ........................................................................................................ 2

3.3 Terms related to measurement ................................................................................................................................................. 3

4 Requirements .......................................................................................................................................................................................................... 4

4.1 Performance requirements .......................................................................................................................................................... 4

4.2 Engineering design .............................................................................................................................................................................. 4

4.2.1 Operator enclosure ........................................................................................................................................................ 4

4.2.2 Air quality control system........................................................................................................................................ 5

4.2.3 Filters and filter housings ........................................................................................................................................ 6

4.3 Monitoring devices .............................................................................................................................................................................. 7

4.3.1 General...................................................................................................................................................................................... 7

4.3.2 Carbon dioxide operator notification system for retrofit installations ............................ 8

4.3.3 Carbon dioxide operator notification system for machine manufacturers ................... 8

4.3.4 Additional monitoring capabilities .................................................................................................................. 9

5 Performance testing.......................................................................................................................................................................................... 9

5.1 Requirements ........................................................................................................................................................................................... 9

5.1.1 Test set up .............................................................................................................................................................................. 9

5.1.2 Test equipment .................................................................................................................................................................. 9

5.1.3 Test methods ....................................................................................................................................................................10

5.2 Test report ................................................................................................................................................................................................12

6 Operation and maintenance instructions ...............................................................................................................................13

Annex A (informative) CO management ......................................................................................................................................................15

Annex B (informative) Recommendations for the operational integration of this document ..............17

Bibliography .............................................................................................................................................................................................................................21

© ISO 2021 – All rights reserved iii
---------------------- Page: 3 ----------------------
ISO 23875:2021(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 82, Mining.

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 2021 – All rights reserved
---------------------- Page: 4 ----------------------
ISO 23875:2021(E)
Introduction

Safety in mining operations is of concern to all involved in owning, developing, managing, and working

in mining environments. Routine mining activities can generate airborne particulates which are

hazardous to human health. Therefore, it is necessary to develop controls which limit the operator’s

exposure to airborne particulates while operating equipment from within the operator enclosure.

With the rise in the number of countries regulating air quality in mining, construction, and industrial

environments, machine manufacturers have become increasingly aware of the need for standard

practices in the design and performance of operator enclosures. This document seeks to address the

fundamental design requirements that will allow for operator enclosures to perform at a level that

provides sustained air quality, reducing concentrations of respirable particulate matter and carbon

dioxide that are harmful to human health. The emphasis of this document is in three areas: 1) design, 2)

air quality control system performance testing, and 3) maintenance and operation instruction for the

operator enclosure.

All operator enclosures, either on new machines or existing machines currently in operation, meeting

the requirements of this document are expected to provide consistent air quality performance. The

technical aspects of an operator enclosure are universal as are the design and performance testing

methods. Therefore, every attempt has been made to make this an inclusive document which addresses

the needs of fixed and mobile operator enclosures.

This document was developed to provide for the occupational health and safety of personnel who work

inside operator enclosures. It primarily addresses air quality concerns by establishing parameters

to determine air quality control system effectiveness. The control of these airborne contaminants is

through an effective air quality control system (for both external air and recirculated air), dilution of

CO , routine testing of the air within the operator enclosure, and effective maintenance throughout

the life cycle of the operator enclosure. Extensive research and subsequent publications have produced

a substantial body of knowledge around the air quality control systems and are the basis of this

document. See Bibliography.
Figure 1 — Air quality control system life cycle

As illustrated in Figure 1, this document presents a life cycle approach to operator enclosure air quality

control system design, performance testing, and maintenance.
© ISO 2021 – All rights reserved v
---------------------- Page: 5 ----------------------
INTERNATIONAL STANDARD ISO 23875:2021(E)
Mining — Air quality control systems for operator
enclosures — Performance requirements and test methods
1 Scope

This document specifies performance and design requirements for air quality control systems for

operator enclosures and their monitoring devices. The design specifications are universal in their

application and do not contemplate specific mining environments. They are intended to meet identified

parameters of both pressurization and respirable particulate and carbon dioxide concentrations.

This document also specifies test methods to assess such parameters and provides operational and

maintenance instructions. Recommendations are made for operational integration of the air quality

control system.

Gases and vapours that can be a hazard in the work environment outside of the operator enclosure are

excluded from this document.
2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any amendments) applies.

ISO 18158, Workplace air — Terminology

ISO 29463-1:2017, High efficiency filters and filter media for removing particles from air — Part 1:

Classification, performance, testing and marking

ISO 29463-2, High-efficiency filters and filter media for removing particles in air — Part 2: Aerosol

production, measuring equipment and particle-counting statistics

ISO 29463-3, High-efficiency filters and filter media for removing particles in air — Part 3: Testing flat

sheet filter media

ISO 29463-4:2011, High-efficiency filters and filter media for removing particles in air — Part 4: Test

method for determining leakage of filter elements - Scan method

ISO 29463-5:2011, High-efficiency filters and filter media for removing particles in air — Part 5: Test

method for filter elements
ISO/IEC 17000, Conformity assessment — Vocabulary and general principles

ISO/IEC 17050-1, Conformity assessment — Supplier's declaration of conformity — Part 1: General

requirements
3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO/IEC 17000, ISO 18158¸

ISO 29463-1 and the following apply.

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/
© ISO 2021 – All rights reserved 1
---------------------- Page: 6 ----------------------
ISO 23875:2021(E)
3.1 Terms related to air quality
3.1.1
airborne particle
airborne particulate
fine matter, in solid or liquid form, dispersed in air

[SOURCE: ISO 18158:2016, 2.1.2.3, modified — The preferred term "airborne particulate" has been added.]

3.1.2
hazardous to human health

in such a quantity and/or quality of airborne particulates (3.1.1) or CO (3.1.7) or noise, that it has

adverse health effects
3.1.3
contaminated environment

area where airborne particulates (3.1.1) hazardous to human health (3.1.2) are present in the ambient air

3.1.4
breathing zone
air space around the worker’s face from where they take their breath
3.1.5
ambient CO level

CO (3.1.7) concentration present in the air outside of the operator enclosure (3.2.1), to which people

can be exposed
3.1.6
respirable particulate matter
materials that are deposited in the gas-exchange region of the lungs

Note 1 to entry: The median cut point for respirable particulate matter is 4,0 μm, according to ISO 7708:1995.

3.1.7
carbon dioxide emitted as a by-product of human respiration
3.2 Terms related to the operator enclosure design
3.2.1
operator enclosure

structure that completely surrounds the operator, preventing the free passage of external air (3.2.7),

dust or other substances into the area around the operator

[SOURCE: ISO 10263-4:2009, 3.1, modified – "part of the machine which" has been replaced with

"structure that".]
3.2.2
air quality control system

operator enclosure (3.2.1) that includes structural components, external air (3.2.7) and recirculation air

systems designed to protect an operator from environmental factors such as dust, heat, cold, wind, and

airborne particulates (3.1.1) hazardous to human health (3.1.2)
3.2.3
sustained quality

quality achieved through designs that work together to create an effective air quality control system

(3.2.2) that allows operator enclosure (3.2.1) pressure and effective filtration to be maintained

continuously between planned maintenance intervals (3.2.4)
2 © ISO 2021 – All rights reserved
---------------------- Page: 7 ----------------------
ISO 23875:2021(E)
3.2.4
planned maintenance interval
interval when routine maintenance is performed
3.2.5
operator enclosure pressurization

situation when the operator enclosure (3.2.1) external air (3.2.7) intake is greater than the operator

enclosure leakage
3.2.6
operator enclosure work environment
space inside the operator enclosure (3.2.1)
3.2.7
external air

controlled air entering the system or opening from outdoors before any air treatment

[SOURCE: ISO 16818:2008, 3.97]
3.3 Terms related to measurement
3.3.1
decay time

time that it takes for the airborne particles (3.1.1) to be removed from the air inside the operator

enclosure work environment (3.2.6)
Note 1 to entry: See Figure 2.

Dust concentration within the operator enclosure starts at 7 µg/m and at the 2-minute interval it begins

to rise. At the 3-minute interval it peaks at 5 000 µg/m , and at the 5-minute interval it returns to 7 µg/

m . In this example, the decay time is two minutes.
Key
X time, min
Y concentration, µg/m
2 min
Figure 2 — Decay time — Example
© ISO 2021 – All rights reserved 3
---------------------- Page: 8 ----------------------
ISO 23875:2021(E)
4 Requirements
4.1 Performance requirements

The air quality control system objective is to prevent ingress of respirable particulate matter from the

contaminated environment, through means of filtration and operator enclosure pressurization. The air

quality control system shall meet the following performance requirements.

a) The maximum sustained CO shall be the ambient level of CO + 400 ppm, refer to Annex A for

2 2
further information.

b) At the start and the end of the decay test, the maximum respirable particulate matter concentration

shall be ≤25 µg/m .
c) The respirable particulate decay time shall be of 120 s maximum.

d) The minimum sustained pressurization, when the machine starting device is in the “on” position

(activating the electrical system) shall be ≥ 20 Pa.
e) The maximum sustained pressurization shall not exceed 200 Pa.
4.2 Engineering design
4.2.1 Operator enclosure
The following requirements shall be met.

a) The machinery safety standard for the specific machine type shall be consulted when designing or

retrofitting an operator enclosure to a machine.

b) If the operator enclosure is built on the machine, the interface with the machine frame shall be

properly sealed to ensure that there are no leakage points created under vibration during machine

operations.

c) Operator ingress, egress, and field of view, and operator enclosure serviceability and maintainability,

shall be considered when retrofitting an operator enclosure with an air quality control system.

d) Operator roll over protective structures (ROPS) and falling-object protective structures (FOPS),

or other protective structure systems, shall not be modified without permission from the machine

manufacturer.

e) Consideration should be given to materials used in the enclosure to ensure that they do not

accumulate particulate and are easily cleaned. Operator seats should be covered in a smooth, easily

cleaned material, for example vinyl.

f) Weld joints or connections in the engine exhaust system, which are prone to leakage over time,

should not be near the external intake air system.

g) The operator enclosure shall be designed such that all ingress points are sealed so that the system

holds pressure. All structural members, such as ROPS and FOPS, weld points, stitch welds, electrical

and hydraulic penetrations, windows, etc. shall ensure that the operator enclosure holds pressure

sufficiently to meet the minimum pressurization performance requirement, see 4.1 d), e).

h) Operator enclosures with air quality control system components and plumbing that are built with

attachment to two different planes shall have means to relieve the vibration stress, for example by

flexible connectors.
4 © ISO 2021 – All rights reserved
---------------------- Page: 9 ----------------------
ISO 23875:2021(E)
4.2.2 Air quality control system
4.2.2.1 General
The following shall be considered.

a) The ventilation system should allow for airflows to be directed away from the operator.

b) Air quality control systems components added to the operator enclosure should be fitted such as

not to impede the field of view of the operator. If visual impediment is unavoidable, an assessment

shall be performed to determine the best mitigation measures, for example through the use of

cameras or mirrors.

c) The air quality control system shall not create levels of noise that are hazardous to human health

or that contribute to existing sources of noise, generating levels hazardous to human health.

d) Filter maintenance intervals shall be considered in the design. Sustained quality requires that

the prefilter be appropriately sized so that it does not require maintenance between the planned

maintenance interval.

e) Prefilters or cyclonic precleaners are recommended to remove airborne particulates from the

external air prior to the primary filter. This prolongs the service life of the filter and allows for the

use of high efficiency filtration. The design solutions referenced in the list below are given in order

of their effectiveness in providing sustained operator enclosure pressurization when operating in

dust conditions typical of mining environments:
1) powered precleaner using an integrated powered cyclonic separator;
2) pressurizer blower using a non-powered cyclonic separator;
3) pressurizer blower using a prefilter;
4) heating ventilation air conditioning (HVAC) blower.

f) Leakage in low-pressure areas in the HVAC system and external filtration cause airborne

particulates to flow directly into the operator enclosure without passing through the external

air filter. Low pressure leakage can occur for a number of reasons, including the integrity of the

external air seal, mounting surfaces, plastic and metal joints, ventilation tubing and attachments.

g) External air shall be ducted directly into the HVAC mixing plenum. Putting external air directly

into the operator enclosure compromises the air quality in the operator enclosure by introducing

humidity and/or heat/cold directly into the operator enclosure. This makes the operator enclosure

the mixing plenum and compromises the air quality control system.

h) The air quality control system shall include a means to pressurize the operator enclosure.

i) External air devices, including the pressurization fan and all filters, shall be in place and switched

on when the machine starting device is in the “on” position (activating the electrical system). This

electrical configuration shall provide for continuous operator enclosure pressurization through the

external pressurizer or through the HVAC blower. Continuous external air, through high efficiency

filtration, prevents particulate ingress into the work environment.

j) When the machine starting device is in the “on” position (activating the electrical system), the

air quality control system shall continuously bring external air into the HVAC mixing plenum to

continuously dilute CO concentrations. CO levels in the air quality control system give a clear

2 2
indication of sufficient air exchange. (See Annex A.)
© ISO 2021 – All rights reserved 5
---------------------- Page: 10 ----------------------
ISO 23875:2021(E)
4.2.2.2 External air and recirculation airflow systems

Air quality is directly related to the efficiency and integrity of the external air and recirculation airflow

filtration systems. The following shall be considered.

a) The air quality control system shall be equipped with an external air filter and a recirculation

airflow filter.

b) High efficiency filtration can restrict airflow, a factor that shall be taken into consideration in HVAC

ventilation design.

NOTE The recirculation filter is the most effective means to rapidly remove the respirable airborne

particulates from within the operator enclosure. High efficiency recirculation filtration allows the

particulate to be removed with a single pass through the filter. The air volume of the operator enclosure can

pass through the recirculation filter several times a minute. By removing the particulate in one pass through

the recirculation filter, air quality is maintained.

c) The air quality control system’s external air intake shall be installed so as to minimize ingress of the

machine’s exhaust emissions. Placement of the external air intake should take into consideration

the exhaust emissions of other machines operating in close proximity.

d) In operator enclosure designs, ventilation should direct airflow from the top half of the operator

enclosure to the bottom half of the operator enclosure. The airflow pattern in the operator

enclosure is a major consideration in the design of the ventilation system. The filtered air coming

from the HVAC should pass over the operator breathing zone and then down to the recirculation

air intake. By placing the supply ventilation in the upper part of the operator enclosure and the

return airflow in the lower part of the operator enclosure, below the seat index point (SIP) as

defined in ISO 5353, the particles move in a downward direction, taking advantage of gravity. The

location of the recirculation filter low in the operator enclosure allows particles that are brought

into the operator enclosure on the boots and vestments of the operator to be drawn into the

high efficiency recirculation filter without passing over the operator breathing zone. This factor

should be considered in operator enclosure ventilation design. While all ventilation configurations

might not follow this recommended airflow pattern, in all cases the operator enclosure air quality

performance shall comply with the performance requirements. [See 4.1 a), b), c), d), e).]

e) External air filtration and recirculation air filtration shall be manufactured, tested, and classified

in accordance with ISO 29463–1, ISO 29463–2, ISO 29463–3, ISO 29463–5 and ISO 29463-4: 2011,

F.1 to F.5.
f) All filters shall be marked with their filter classification.

g) Filters shall be labelled in accordance with ISO 29463-1:2017, 9.1 a), b), c), d) e), f). If applicable,

ISO 29463-5: 2011, Clause B.5, shall be included as a separate document in the filter packaging. Use

of a machine-readable optical label (e.g. matrix barcode) on the filter label is recommended to allow

for retrieval of the filter label information.
4.2.3 Filters and filter housings
4.2.3.1 General

Filter housings provide the delivery system for the operator enclosure filtration. Protection of the filter

is critical to sustained quality and operator enclosure air quality performance.
4.2.3.2 Filter housings
The following items should be addressed in the filter housing:
a) the filter cannot be installed incorrectly (e.g. reversed airflow);
b) the filter housing is easily cleaned to avoid accumulation of particles;
6 © ISO 2021 – All rights reserved
---------------------- Page: 11 ----------------------
ISO 23875:2021(E)
c) all surfaces are easily cleaned;
d) edges, projections, and recesses are reduced or eliminated;

e) filters are easily removed and replaced without damaging the filter media or filter seal;

f) interior surfaces are smooth without ridges or crevices that can collect particles;

g) filter housing shall mate with the filter seal to insure zero seal leakage;

h) vibration and shock do not have an adverse effect of filter seal effectiveness.

4.2.3.3 Handling instructions for filter media made from glass fibre

A primary cause of filter leakage is damage to the media during shipping, removal from the packaging

and installation on the machine. Glass fibre media is particularly susceptible to fibre breakage,

puncture holes, water wicking, and fibre abrasion from vibration. For every step in the process, from

manufacture to final installation, the filter efficiencies shall be maintained as classified.

The following requirements shall be met.
a) Handling instructions shall be provided on the label and packaging.
b) Packaging shall protect the media from excessive shock during shipping.

c) Labelling of the filter packaging shall include a warning not to touch the media.

d) Handling instructions for how to remove the filter from its original packaging without damaging

the filter should be printed on the outside of the product packaging.

e) Filter shall be constructed with a protective screen to prevent damage, which is caused by touching

the filter media when being removed from its packaging or when it is being installed into the

machine.
4.3 Monitoring devices
4.3.1 General

Continuous monitoring is the means by which system performance is validated and maintained. The air

quality control monitoring device shall be integrated into the air quality control system. Both pressure

and CO shall be monitored.
The pressure monitoring device shall have the following minimum features.
a) A minimum resolution of 5 Pa.
b) A minimum accuracy of ± 10 Pa.
The carbon dioxide monitoring device shall have the following minimum features.
a) Nondispersive infrared sensor (NDIR).
b) Range: 0,0 to 5 000 ppm.
c) Accuracy: ± 3,0 % of reading.
d) Response time: 20 s.

e) Altitude compensation — Due to variations in temperature and atmospheric pressure, air volumes

change at different altitudes. The device shall have a temperature and atmospheric pressure

sensor to automatically compensate for changes in these conditions to provide accurate CO

measurements.
© ISO 2021 – All rights reserved 7
---------------------- Page: 12
...

INTERNATIONAL ISO
STANDARD 23875
First edition
Mining — Air quality control systems
for operator enclosures —
Performance requirements and test
methods
PROOF/ÉPREUVE
Reference number
ISO 23875:2021(E)
ISO 2021
---------------------- Page: 1 ----------------------
ISO 23875:2021(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2021

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
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii PROOF/ÉPREUVE © ISO 2021 – All rights reserved
---------------------- Page: 2 ----------------------
ISO 23875:2021(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

3.1 Terms related to air quality .......................................................................................................................................................... 2

3.2 Terms related to the operator enclosure design ........................................................................................................ 2

3.3 Terms related to measurement ................................................................................................................................................. 3

4 Requirements .......................................................................................................................................................................................................... 4

4.1 Performance requirements .......................................................................................................................................................... 4

4.2 Engineering design .............................................................................................................................................................................. 4

4.2.1 Operator enclosure ........................................................................................................................................................ 4

4.2.2 Air quality control system........................................................................................................................................ 5

4.2.3 Filters and filter housings ........................................................................................................................................ 6

4.3 Monitoring devices .............................................................................................................................................................................. 7

4.3.1 General...................................................................................................................................................................................... 7

4.3.2 Carbon dioxide operator notification system for retrofit installations ............................ 8

4.3.3 Carbon dioxide operator notification system for machine manufacturers ................... 8

4.3.4 Additional monitoring capabilities .................................................................................................................. 9

5 Performance testing.......................................................................................................................................................................................... 9

5.1 Requirements ........................................................................................................................................................................................... 9

5.1.1 Test set up .............................................................................................................................................................................. 9

5.1.2 Test equipment .................................................................................................................................................................. 9

5.1.3 Test methods ....................................................................................................................................................................10

5.2 Test report ................................................................................................................................................................................................12

6 Operation and maintenance instructions ...............................................................................................................................13

Annex A (informative) CO management ......................................................................................................................................................15

Annex B (informative) Recommendations for the operational integration of this document ..............17

Bibliography .............................................................................................................................................................................................................................21

© ISO 2021 – All rights reserved PROOF/ÉPREUVE iii
---------------------- Page: 3 ----------------------
ISO 23875:2021(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 82, Mining.

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 PROOF/ÉPREUVE © ISO 2021 – All rights reserved
---------------------- Page: 4 ----------------------
ISO 23875:2021(E)
Introduction

Safety in mining operations is of concern to all involved in owning, developing, managing, and working

in mining environments. Routine mining activities can generate airborne particulates which are

hazardous to human health. Therefore, it is necessary to develop controls which limit the operator’s

exposure to airborne particulates while operating equipment from within the operator enclosure.

With the rise in the number of countries regulating air quality in mining, construction, and industrial

environments, machine manufacturers have become increasingly aware of the need for standard

practices in the design and performance of operator enclosures. This document seeks to address the

fundamental design requirements that will allow for operator enclosures to perform at a level that

provides sustained air quality, reducing concentrations of respirable particulate matter and carbon

dioxide that are harmful to human health. The emphasis of this document is in three areas: 1) design, 2)

air quality control system performance testing, and 3) maintenance and operation instruction for the

operator enclosure.

All operator enclosures, either on new machines or existing machines currently in operation, meeting

the requirements of this document are expected to provide consistent air quality performance. The

technical aspects of an operator enclosure are universal as are the design and performance testing

methods. Therefore, every attempt has been made to make this an inclusive document which addresses

the needs of fixed and mobile operator enclosures.

This document was developed to provide for the occupational health and safety of personnel who work

inside operator enclosures. It primarily addresses air quality concerns by establishing parameters

to determine air quality control system effectiveness. The control of these airborne contaminants is

through an effective air quality control system (for both external air and recirculated air), dilution of

CO , routine testing of the air within the operator enclosure, and effective maintenance throughout

the life cycle of the operator enclosure. Extensive research and subsequent publications have produced

a substantial body of knowledge around the air quality control systems and are the basis of this

document. See Bibliography.
Figure 1 — Air quality control system life cycle

As illustrated in Figure 1, this document presents a life cycle approach to operator enclosure air quality

control system design, performance testing, and maintenance.
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INTERNATIONAL STANDARD ISO 23875:2021(E)
Mining – Air quality control systems for operator
enclosures – Performance requirements and test methods
1 Scope

This document specifies performance and design requirements for air quality control systems for

operator enclosures and their monitoring devices. The design specifications are universal in their

application and do not contemplate specific mining environments. They are intended to meet identified

parameters of both pressurization and respirable particulate and carbon dioxide concentrations.

This document also specifies test methods to assess such parameters and provides operational and

maintenance instructions. Recommendations are made for operational integration of the air quality

control system.

Gases and vapours that can be a hazard in the work environment outside of the operator enclosure are

excluded from this document.
2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any amendments) applies.

ISO 18158, Workplace air — Terminology

ISO 29463-1:2017, High efficiency filters and filter media for removing particles from air — Part 1:

Classification, performance, testing and marking

ISO 29463-2, High-efficiency filters and filter media for removing particles in air — Part 2: Aerosol

production, measuring equipment and particle-counting statistics

ISO 29463-3, High-efficiency filters and filter media for removing particles in air — Part 3: Testing flat

sheet filter media

ISO 29463-4:2011, High-efficiency filters and filter media for removing particles in air — Part 4: Test

method for determining leakage of filter elements - Scan method

ISO 29463-5:2011, High-efficiency filters and filter media for removing particles in air — Part 5: Test

method for filter elements
ISO/IEC 17000, Conformity assessment — Vocabulary and general principles

ISO/IEC 17050-1, Conformity assessment — Supplier's declaration of conformity — Part 1: General

requirements
3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO/IEC 17000, ISO 18158¸

ISO 29463-1 and the following apply.

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/
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ISO 23875:2021(E)
3.1 Terms related to air quality
3.1.1
airborne particle
airborne particulate
fine matter, in solid or liquid form, dispersed in air

[SOURCE: ISO 18158:2016, 2.1.2.3, modified — The preferred term "airborne particulate" has been added.]

3.1.2
hazardous to human health

in such a quantity and/or quality of airborne particulates (3.1.1) or CO (3.1.7) or noise, that it has

adverse health effects
3.1.3
contaminated environment

area where airborne particulates (3.1.1) hazardous to human health (3.1.2) are present in the ambient air

3.1.4
breathing zone
air space around the worker’s face from where they take their breath
3.1.5
ambient CO level

CO (3.1.7) concentration present in the air outside of the operator enclosure (3.2.1), to which people

can be exposed
3.1.6
respirable particulate matter
materials that are deposited in the gas-exchange region of the lungs

Note 1 to entry: The median cut point for respirable particulate matter is 4,0 μm, according to ISO 7708:1995.

3.1.7
carbon dioxide emitted as a by-product of human respiration
3.2 Terms related to the operator enclosure design
3.2.1
operator enclosure

structure that completely surrounds the operator, preventing the free passage of external air (3.2.7),

dust or other substances into the area around the operator

[SOURCE: ISO 10263-4:2009, 3.1, modified – "part of the machine which" has been replaced with

"structure that".]
3.2.2
air quality control system

operator enclosure (3.2.1) that includes structural components, external air (3.2.7) and recirculation air

systems designed to protect an operator from environmental factors such as dust, heat, cold, wind, and

airborne particulates (3.1.1) hazardous to human health (3.1.2)
3.2.3
sustained quality

quality achieved through designs that work together to create an effective air quality control system

(3.2.2) that allows operator enclosure (3.2.1) pressure and effective filtration to be maintained

continuously between planned maintenance intervals (3.2.4)
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ISO 23875:2021(E)
3.2.4
planned maintenance interval
interval when routine maintenance is performed
3.2.5
operator enclosure pressurization

situation when the operator enclosure (3.2.1) external air (3.2.7) intake is greater than the operator

enclosure leakage
3.2.6
operator enclosure work environment
space inside the operator enclosure (3.2.1)
3.2.7
external air

controlled air entering the system or opening from outdoors before any air treatment

[SOURCE: ISO 16818:2008, 3.97]
3.3 Terms related to measurement
3.3.1
decay time

time that it takes for the airborne particles (3.1.1) to be removed from the air inside the operator

enclosure work environment (3.2.6)
Note 1 to entry: See Figure 2.

Dust concentration within the operator enclosure starts at 7 µg/m and at the 2-minute interval it begins

to rise. At the 3-minute interval it peaks at 5 000 µg/m , and at the 5-minute interval it returns to 7 µg/

m . In this example, the decay time is two minutes.
Key
X time, min
Y concentration, µg/m
2 min
Figure 2 — Decay time — Example
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ISO 23875:2021(E)
4 Requirements
4.1 Performance requirements

The air quality control system objective is to prevent ingress of respirable particulate matter from the

contaminated environment, through means of filtration and operator enclosure pressurization. The air

quality control system shall meet the following performance requirements.

a) The maximum sustained CO shall be the ambient level of CO + 400 ppm, refer to Annex A for

2 2
further information.

b) At the start and the end of the decay test, the maximum respirable particulate matter concentration

shall be ≤25 µg/m .
c) The respirable particulate decay time shall be of 120 s maximum.

d) The minimum sustained pressurization, when the machine starting device is in the “on” position

(activating the electrical system) shall be ≥ 20 Pa.
e) The maximum sustained pressurization shall not exceed 200 Pa.
4.2 Engineering design
4.2.1 Operator enclosure
The following requirements shall be met.

a) The machinery safety standard for the specific machine type shall be consulted when designing or

retrofitting an operator enclosure to a machine.

b) If the operator enclosure is built on the machine, the interface with the machine frame shall be

properly sealed to ensure that there are no leakage points created under vibration during machine

operations.

c) Operator ingress, egress, and field of view, and operator enclosure serviceability and maintainability,

shall be considered when retrofitting an operator enclosure with an air quality control system.

d) Operator roll over protective structures (ROPS) and falling-object protective structures (FOPS),

or other protective structure systems, shall not be modified without permission from the machine

manufacturer.

e) Consideration should be given to materials used in the enclosure to ensure that they do not

accumulate particulate and are easily cleaned. Operator seats should be covered in a smooth, easily

cleaned material, for example vinyl.

f) Weld joints or connections in the engine exhaust system, which are prone to leakage over time,

should not be near the external intake air system.

g) The operator enclosure shall be designed such that all ingress points are sealed so that the system

holds pressure. All structural members, such as ROPS and FOPS, weld points, stitch welds, electrical

and hydraulic penetrations, windows, etc. shall ensure that the operator enclosure holds pressure

sufficiently to meet the minimum pressurization performance requirement, see 4.1 d), e).

h) Operator enclosures with air quality control system components and plumbing that are built with

attachment to two different planes shall have means to relieve the vibration stress, for example by

flexible connectors.
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ISO 23875:2021(E)
4.2.2 Air quality control system
4.2.2.1 General
The following shall be considered.

a) The ventilation system should allow for airflows to be directed away from the operator.

b) Air quality control systems components added to the operator enclosure should be fitted such as

not to impede the field of view of the operator. If visual impediment is unavoidable, an assessment

shall be performed to determine the best mitigation measures, for example through the use of

cameras or mirrors.

c) The air quality control system shall not create levels of noise that are hazardous to human health

or that contribute to existing sources of noise, generating levels hazardous to human health.

d) Filter maintenance intervals shall be considered in the design. Sustained quality requires that

the prefilter be appropriately sized so that it does not require maintenance between the planned

maintenance interval.

e) Prefilters or cyclonic precleaners are recommended to remove airborne particulates from the

external air prior to the primary filter. This prolongs the service life of the filter and allows for the

use of high efficiency filtration. The design solutions referenced in the list below are given in order

of their effectiveness in providing sustained operator enclosure pressurization when operating in

dust conditions typical of mining environments:
1) powered precleaner using an integrated powered cyclonic separator;
2) pressurizer blower using a non-powered cyclonic separator;
3) pressurizer blower using a prefilter;
4) heating ventilation air conditioning (HVAC) blower.

f) Leakage in low-pressure areas in the HVAC system and external filtration cause airborne

particulates to flow directly into the operator enclosure without passing through the external

air filter. Low pressure leakage can occur for a number of reasons, including the integrity of the

external air seal, mounting surfaces, plastic and metal joints, ventilation tubing and attachments.

g) External air shall be ducted directly into the HVAC mixing plenum. Putting external air directly

into the operator enclosure compromises the air quality in the operator enclosure by introducing

humidity and/or heat/cold directly into the operator enclosure. This makes the operator enclosure

the mixing plenum and compromises the air quality control system.

h) The air quality control system shall include a means to pressurize the operator enclosure.

i) External air devices, including the pressurization fan and all filters, shall be in place and switched

on when the machine starting device is in the “on” position (activating the electrical system). This

electrical configuration shall provide for continuous operator enclosure pressurization through the

external pressurizer or through the HVAC blower. Continuous external air, through high efficiency

filtration, prevents particulate ingress into the work environment.

j) When the machine starting device is in the “on” position (activating the electrical system), the

air quality control system shall continuously bring external air into the HVAC mixing plenum to

continuously dilute CO concentrations. CO levels in the air quality control system give a clear

2 2
indication of sufficient air exchange. (See Annex A.)
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ISO 23875:2021(E)
4.2.2.2 External air and recirculation airflow systems

Air quality is directly related to the efficiency and integrity of the external air and recirculation airflow

filtration systems. The following shall be considered.

a) The air quality control system shall be equipped with an external air filter and a recirculation

airflow filter.

b) High efficiency filtration can restrict airflow, a factor that shall be taken into consideration in HVAC

ventilation design.

NOTE The recirculation filter is the most effective means to rapidly remove the respirable airborne

particulates from within the operator enclosure. High efficiency recirculation filtration allows the

particulate to be removed with a single pass through the filter. The air volume of the operator enclosure can

pass through the recirculation filter several times a minute. By removing the particulate in one pass through

the recirculation filter, air quality is maintained.

c) The air quality control system’s external air intake shall be installed so as to minimize ingress of the

machine’s exhaust emissions. Placement of the external air intake should take into consideration

the exhaust emissions of other machines operating in close proximity.

d) In operator enclosure designs, ventilation should direct airflow from the top half of the operator

enclosure to the bottom half of the operator enclosure. The airflow pattern in the operator

enclosure is a major consideration in the design of the ventilation system. The filtered air coming

from the HVAC should pass over the operator breathing zone and then down to the recirculation

air intake. By placing the supply ventilation in the upper part of the operator enclosure and the

return airflow in the lower part of the operator enclosure, below the seat index point (SIP) as

defined in ISO 5353, the particles move in a downward direction, taking advantage of gravity. The

location of the recirculation filter low in the operator enclosure allows particles that are brought

into the operator enclosure on the boots and vestments of the operator to be drawn into the

high efficiency recirculation filter without passing over the operator breathing zone. This factor

should be considered in operator enclosure ventilation design. While all ventilation configurations

might not follow this recommended airflow pattern, in all cases the operator enclosure air quality

performance shall comply with the performance requirements. [See 4.1 a), b), c), d), e).]

e) External air filtration and recirculation air filtration shall be manufactured, tested, and classified

in accordance with ISO 29463–1, ISO 29463–2, ISO 29463–3, ISO 29463–5 and ISO 29463-4: 2011,

F.1 to F.5.
f) All filters shall be marked with their filter classification.

g) Filters shall be labelled in accordance with ISO 29463-1:2017, 9.1 a), b), c), d) e), f). If applicable,

ISO 29463-5: 2011, Clause B.5, shall be included as a separate document in the filter packaging. Use

of a machine-readable optical label (e.g. matrix barcode) on the filter label is recommended to allow

for retrieval of the filter label information.
4.2.3 Filters and filter housings
4.2.3.1 General

Filter housings provide the delivery system for the operator enclosure filtration. Protection of the filter

is critical to sustained quality and operator enclosure air quality performance.
4.2.3.2 Filter housings
The following items should be addressed in the filter housing:
a) the filter cannot be installed incorrectly (e.g. reversed airflow);
b) the filter housing is easily cleaned to avoid accumulation of particles;
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ISO 23875:2021(E)
c) all surfaces are easily cleaned;
d) edges, projections, and recesses are reduced or eliminated;

e) filters are easily removed and replaced without damaging the filter media or filter seal;

f) interior surfaces are smooth without ridges or crevices that can collect particles;

g) filter housing shall mate with the filter seal to insure zero seal leakage;

h) vibration and shock do not have an adverse effect of filter seal effectiveness.

4.2.3.3 Handling instructions for filter media made from glass fibre

A primary cause of filter leakage is damage to the media during shipping, removal from the packaging

and installation on the machine. Glass fibre media is particularly susceptible to fibre breakage,

puncture holes, water wicking, and fibre abrasion from vibration. For every step in the process, from

manufacture to final installation, the filter efficiencies shall be maintained as classified.

The following requirements shall be met.
a) Handling instructions shall be provided on the label and packaging.
b) Packaging shall protect the media from excessive shock during shipping.

c) Labelling of the filter packaging shall include a warning not to touch the media.

d) Handling instructions for how to remove the filter from its original packaging without damaging

the filter should be printed on the outside of the product packaging.

e) Filter shall be constructed with a protective screen to prevent damage, which is caused by touching

the filter media when being removed from its packaging or when it is being installed into the

machine.
4.3 Monitoring devices
4.3.1 General

Continuous monitoring is the means by which system performance is validated and maintained. The air

quality control monitoring device shall be integrated into the air quality control system. Both pressure

and CO shall be monitored.
The pressure monitoring device shall have the following minimum features.
a) A minimum resolution of 5 Pa.
b) A minimum accuracy of ± 10 Pa.
The carbon dioxide monitoring device shall have the following minimum features.
a) Nondispersive infrared sensor (NDIR).
b) Range: 0,0 to 5 000 ppm.
c) Accuracy: ± 3,0 % of reading.
d) Response time: 20 s.

e) Altitude compensation — Due to variations in temperature and atmospheric pressure, air volumes

change at different altitudes. The device shall have a temperature and atmospheric pressure

sensor to automatically compensate for cha
...

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