Classification of environmental conditions - Part 2-7: Environmental conditions appearing in nature - Fauna and flora

IEC 60721-2-7:2018 addresses the occurrence of fauna and flora, including its main effects on electrotechnical products. Exposure and damage from the effects of fauna and flora can occur at almost any time in a product's life cycle. Moreover, there are many agents of attack with various actions.
This second edition cancels and replaces the first edition published in 1987. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous edition:
- This edition has been entirely rewritten.
This bilingual version (2018-11) corresponds to the monolingual English version, published in 2018-03.
The French version of this standard has not been voted upon.

Classification des conditions d’environnement – Partie 2-7: Conditions d’environnement présentes dans la nature – Faune et flore

L'IEC 60721-2-7:2018 aborde la présence de la faune et de la flore, notamment ses principaux effets sur les produits électrotechniques. L’exposition aux effets de la faune et de la flore, ainsi que les dommages en résultant, peuvent survenir à tout moment du cycle de vie d’un produit. Par ailleurs, il existe de nombreux agents d’attaque par différentes actions.
Cette deuxième édition annule et remplace la première édition parue en 1987. Cette édition constitue une révision technique.
Cette édition inclut les modifications techniques majeures suivantes par rapport à l'édition précédente:
- La présente édition a été entièrement réécrite.
La présente version bilingue (2018-11) correspond à la version anglaise monolingue publiée en 2018-03.
La version française de cette norme n'a pas été soumise au vote.

General Information

Status
Published
Publication Date
18-Mar-2018
Current Stage
PPUB - Publication issued
Start Date
19-Mar-2018
Completion Date
19-Mar-2018
Ref Project

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IEC 60721-2-7
Edition 2.0 2018-03
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Classification of environmental conditions –
Part 2-7: Environmental conditions appearing in nature – Fauna and flora
Classification des conditions d’environnement –
Partie 2-7: Conditions d’environnement présentes dans la nature –Faune et flore
IEC 60721-2-7:2018-03(en-fr)
---------------------- Page: 1 ----------------------
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---------------------- Page: 2 ----------------------
IEC 60721-2-7
Edition 2.0 2018-03
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Classification of environmental conditions –
Part 2-7: Environmental conditions appearing in nature – Fauna and flora
Classification des conditions d’environnement –
Partie 2-7: Conditions d’environnement présentes dans la nature –Faune et flore
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 19.040 ISBN 978-2-8322-6246-7

Warning! Make sure that you obtained this publication from an authorized distributor.

Attention! Veuillez vous assurer que vous avez obtenu cette publication via un distributeur agréé.

® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale
---------------------- Page: 3 ----------------------
– 2 – IEC 60721-2-7:2018 © IEC 2018
CONTENTS

FOREWORD ........................................................................................................................... 3

1 Scope .............................................................................................................................. 5

2 Normative references ...................................................................................................... 5

3 Terms and definitions ...................................................................................................... 5

4 General ........................................................................................................................... 5

5 Occurrence of fauna and flora ......................................................................................... 6

5.1 Fungi ...................................................................................................................... 6

5.1.1 Background ..................................................................................................... 6

5.1.2 Growth and survival factors ............................................................................. 6

5.1.3 Habitat and geographical distribution ............................................................... 7

5.1.4 Effects of fungi on materials ............................................................................ 8

5.2 Bacteria ................................................................................................................ 11

5.2.1 Background ................................................................................................... 11

5.2.2 Growth and survival factors ........................................................................... 11

5.2.3 Habitat ........................................................................................................... 12

5.2.4 Effects of bacteria on materials...................................................................... 12

5.3 Insects .................................................................................................................. 13

5.3.1 Background ................................................................................................... 13

5.3.2 Habitat ........................................................................................................... 14

5.3.3 Effects of insects on materials ....................................................................... 14

5.4 Rodents ................................................................................................................ 14

5.4.1 Background ................................................................................................... 14

5.4.2 Effects of rodents on materials ...................................................................... 14

5.5 Algae and marine organisms ................................................................................. 15

5.5.1 Algae ............................................................................................................. 15

5.5.2 Borers ........................................................................................................... 15

5.5.3 Fouling organisms ......................................................................................... 15

Bibliography .......................................................................................................................... 16

Figure 1 – Map of regions with different degrees of fungal corrosion ....................................... 8

Table 1 – List of fungus resistant materials ............................................................................. 9

Table 2 – List of potential fungus nutrient materials .............................................................. 10

---------------------- Page: 4 ----------------------
IEC 60721-2-7:2018 © IEC 2018 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
CLASSIFICATION OF ENVIRONMENTAL CONDITIONS –
Part 2-7: Environmental conditions appearing in nature –
Fauna and flora
FOREWORD

1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising

all national electrotechnical committees (IEC National Committees). The object of IEC is to promote

international co-operation on all questions concerning standardization in the electrical and electronic fields. To

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closely with the International Organization for Standardization (ISO) in accordance with conditions determined

by agreement between the two organizations.

2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international

consensus of opinion on the relevant subjects since each technical committee has representation from all

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3) IEC Publications have the form of recommendations for international use and are accepted by IEC National

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between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in

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5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity

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services carried out by independent certification bodies.

6) All users should ensure that they have the latest edition of this publication.

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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is

indispensable for the correct application of this publication.

9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of

patent rights. IEC shall not be held responsible for identifying any or all such patent rights.

International Standard IEC 60721-2-7 has been prepared by IEC technical committee 104:

Environmental conditions, classification and methods of test.

This bilingual version (2018-11) corresponds to the monolingual English version, published in

2018-03.

This second edition cancels and replaces the first edition published in 1987. This edition

constitutes a technical revision.

This edition includes the following significant technical changes with respect to the previous

edition:
a) This edition has been entirely rewritten.
---------------------- Page: 5 ----------------------
– 4 – IEC 60721-2-7:2018 © IEC 2018
The text of this International Standard is based on the following documents:
CDV Report on voting
104/741/CDV 104/792/RVC

Full information on the voting for the approval of this International Standard can be found in

the report on voting indicated in the above table.
The French version of this standard has not been voted upon.

This document has been drafted in accordance with the ISO/IEC Directives, Part 2.

A list of all parts in the IEC 60721 series, published under the general title Classification of

environmental conditions, can be found on the IEC website.

The committee has decided that the contents of this document will remain unchanged until the

stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to

the specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
---------------------- Page: 6 ----------------------
IEC 60721-2-7:2018 © IEC 2018 – 5 –
CLASSIFICATION OF ENVIRONMENTAL CONDITIONS –
Part 2-7: Environmental conditions appearing in nature –
Fauna and flora
1 Scope

This document addresses the occurrence of fauna and flora, including its main effects on

electrotechnical products. Exposure and damage from the effects of fauna and flora can occur

at almost any time in a product's life cycle. Moreover, there are many agents of attack with

various actions.

This document addresses the occurrence and damage arising from fauna and flora in all

locations a product can be stored, transported or used. Generally, fauna can be present and

cause damage to products in both the natural environments experienced in open-air locations

as well as in artificially created environments, such as in a warehouse or building. However,

flora will predominantly be present and cause damage to products only in open-air locations.

Fungus and bacteria can be present in both open-air locations as well as in warehouses or

buildings.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
No terms and definitions are listed in this document.

ISO and IEC maintain terminological databases for use in standardization at the following

addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
4 General

The main attacking agents considered in this document are micro-organisms including fungi,

bacteria, as well as insects, rodents, algae and marine organisms. Hazards due to other

agents are considered to be of lesser importance and have been omitted. These include the

corrosive action of juices secreted by some plants, the mechanical action due to the growth of

the larger trees, which may be sufficiently great to destroy the foundations of a building or to

break cables, and the damage caused by animals such as monkeys and elephants. Birds in

flight can be a hazard to aircraft, and in the region of bird colonies, widespread droppings can

create corrosion problems. In addition, some agents which are mentioned have other modes

of action which have not been included; for example both rodents and insects are occasionally

responsible for chemical corrosion or soiling.

The frequency of occurrence of fauna and flora with a possibility of damaging products very

much depends on conditions of temperature and humidity. In geographical areas with warm

damp climates, fauna and flora, especially insects and micro-organisms such as mould and

bacteria, will find favourable conditions of life. Moreover, humid or wet rooms in buildings, or

rooms for processes producing humidity, are suitable living spaces for rodents, insects and

micro-organisms.
---------------------- Page: 7 ----------------------
– 6 – IEC 60721-2-7:2018 © IEC 2018

Fauna and flora can affect products in various ways, the most important of which are given in

the following examples.

a) Deterioration by physical attack: The functioning of products may be affected by physical

attacks of fauna and flora. The materials of a product may be attacked by fauna,

particularly by rodents and insects, by the actions of feeding from material, gnawing at

material, eating into material, chewing material or cutting holes into material. The severe

damage arising from the physical attack by termites is especially emphasized in this

respect. Among materials susceptible to attack are natural materials such as wood, paper,

leather, textiles, but also plastic materials, including elastomers and even some metals

such as tin and lead.

b) Deterioration by deposits: The functioning of products may be affected by deposits

originating from fauna and flora. These surface deposits affect the products by chemical

and mechanical reactions. Deposits from fauna, especially from insects, rodents, birds,

etc., may consist of elements such as the presence of the animal itself, the building of

nests or settlements, feed stock as well as the metabolic products such as excrements,

enzymes. Deposits from all kinds of flora may consist of material such as detached parts

of plants (leaves, blossom, seeds, fruits, etc.), growth layers of cultures of moulds or

bacteria and effects of their metabolic products.
5 Occurrence of fauna and flora
5.1 Fungi
5.1.1 Background

The name fungus is used to denote members of a large heterogeneous group of organisms, of

which there are about a hundred thousand known species. Most fungi are so small that they

can be observed only with the aid of a microscope. The terms 'mould' and 'mildew', although

not exactly defined in the biological sense, are used by both biologists and laymen to refer to

small non-parasitic fungi, such as those which do not live on other living organisms.

A fungus can, in general, be divided into two parts: the vegetative and the reproductive. The

vegetative part, known as the hypha, is essentially a threadlike filament normally having a

diameter between 2 μm and 20 μm and may be several centimetres long. In the simplest fungi

the hyphae are merely continuous tubes of living matter; in others they are divided by cell

walls, called septa, into separate cells. Collectively the hyphae are referred to as the

mycelium. The mycelium, together with the reproductive spores, is commonly observed on

mouldy bread, shoes, oranges, etc.

In the vast majority of cases the unit of reproduction is the spore. Normally it is unicellular and

microscopic, though occasionally, giants 500 μm in length occur. They may be produced

directly via the hyphae or from a structure created for this specific purpose, as in the

mushroom. From a functional viewpoint spores may be divided into two classes each of which

may be produced by the same organism: those which can be produced rapidly and in large

numbers but have little resistance to adverse environmental factors, and those which are

comparatively few in number but much more resistant to adverse conditions. The former

enable the fungus to spread rapidly during good growing conditions and the latter enable it to

survive hard times such as winter or drought and have been known to survive for many years

in a dry condition.
5.1.2 Growth and survival factors

In order to adapt themselves to changes in their environment or food supply, most species of

fungi can slightly change their characteristics and needs over several generations. This may

be a very short time; in many cases the whole cycle from spore to spore can be completed in

a few days. In addition, it should be noted that the conditions required for the production and

dispersal of spores are generally more exacting than those for growth and survival.

---------------------- Page: 8 ----------------------
IEC 60721-2-7:2018 © IEC 2018 – 7 –

The precise minimum, maximum and optimum temperatures for growth appear to be a matter

of debate between the various authorities. This may be because these values vary from one

species to another. However, in general, the minimum is 2 °C to 5 °C, the maximum 40 °C to

50 °C and the optimum 22 °C to 27 °C. In addition, there are a few fungi that can grow at and

below 0 °C, and one species has been reported growing at a maximum of 62 °C. They are, of

course, capable of surviving even greater extremes in a quiescent state.

The optimum humidity for the growth of nearly all moulds is a relative humidity of 95 % to

100 %. If submerged in water, however, most fungi will not grow. Any reduction from this

optimum will mean a reduced growth rate and few species will grow in a relative humidity of

less than 70 %. Optimum growth conditions also occur in still air.

A suitable source of carbon that can be absorbed as food is essential to fungi for their growth.

Almost all naturally occurring carbon containing compounds, together with many synthetic

organic compounds of a similar structure can be used by fungi as a source of food. All fungi

can utilize an organic supply of nitrogen and a few can also use an inorganic source such as

ammonia. Nitrogen, other than as a gas, is essential for the growth of fungi.

Most fungi are strictly aerobic, that is they cannot grow in complete absence of free oxygen.

In the small number of cases where fungi grow in water, they always do so in a few

centimetres near the surface.

Other elements required for the growth of fungi include sulfur (as sulfate), potassium,

phosphorus (as phosphate) and magnesium. In some cases minute traces of iron, zinc,

manganese, molybdenum, or calcium are required, though in such small quantities that only in

a few fungi is there a clear picture of these requirements. Some fungi also require a supply of

certain vitamins for growth.

Ultra-violet is known to inhibit the growth of most fungi, although daylight normally has no

effect. In a very few instances daylight can influence growth and indeed can cause it to

increase. However, the production and dispersal of spores is dependent upon the presence of

light for many species.

Most fungi grow best in a slightly acid medium within the range pH 5 to pH 6,5. This varies

from one species to another, but few will grow at all below pH 3 or above pH 9.
5.1.3 Habitat and geographical distribution

Since fungi can survive adverse growth conditions in a quiescent state and can gradually

evolve to survive more extreme conditions, and since new species are still being identified, it

is not possible to define exactly the geographical areas in which fungi will grow. There are,

however, certain tendencies which are relevant.

Fungi of one sort or another are found in the soil, water and air over a large part of the earth's

surface, whilst others live on or upon both living and dead animals and plants. Those found in

the air do not grow there, but are in the form of spores. Most live in the soil and only about

2 % live in water; in both cases they grow in the few centimetres just below the surface.

The best conditions for most types of mould growth are in humid tropical areas, although

deterioration due to mould is not confined to the tropics. Equally serious damage can occur in

temperate regions, though not so rapidly, and at least one species of mould is often found in

the form of spores in the air over arctic regions.

Conditions favourable for mould growth may easily be created artificially inside a building or

equipment. Those which are parasitic upon particular animals or plants are among the few

which are restricted to geographical regions.
---------------------- Page: 9 ----------------------
– 8 – IEC 60721-2-7:2018 © IEC 2018

The map in Figure 1 shows areas in which climatic conditions are most favourable for fungal

corrosion. It is based on an analysis of relative humidity and temperature data from

approximately two thousand meteorological stations throughout the world, as follows:

a) Region A – includes areas with at least one month a year in which the mean monthly

relative humidity is from 70 % to 75 % in the hours from 12:00 h (noon) to 14:00 h, and

with a mean monthly minimum temperature at the same time of not less than 15 °C.

b) Region B – includes areas where the equivalent relative humidity is from 75 % to 80 %,

again with the same temperature as Region A.

c) Region C – includes areas where the equivalent relative humidity is greater than 80 %,

again with the same temperature as Region A.
IEC
Figure 1 – Map of regions with different degrees of fungal corrosion

It should be noted that the above climatic conditions do not take account of other naturally

occurring factors mentioned earlier, such as air flow. It also does not cover cases where

favourable conditions may be artificially induced, inside buildings or containers for example.

Nevertheless, within these limits, it does provide a useful indication of the natural liability to

attack by micro-organisms.
5.1.4 Effects of fungi on materials

Unlike most plants, fungi contain no chlorophyll, the green colouring matter with which plants

utilize the sun's energy to manufacture their food from absorbed raw materials. Thus they

have to rely on the food in the substratum on which they grow. However, the structure of the

cell walls only allows them to absorb this food if it is in solution. To achieve this, the fungi

secrete enzymes via their hyphae. This substance converts the food into a soluble form which

can then be readily absorbed.

There are three ways in which fungi may cause damage. Each can occur independently, or in

association with one or both of the others:
---------------------- Page: 10 ----------------------
IEC 60721-2-7:2018 © IEC 2018 – 9 –

1) A material may be a food for the fungi, in which case the material is gradually eaten away.

2) The waste products of fungi are excreted as juices, many of which are corrosive and

cause damage to the substrate on which the fungi are growing. Thus it is possible for

fungi to damage a material even though it is not a source of food. For example the minute

impurities in finger prints on glass have been known to support growths whose corrosive

waste products have etched the surface of the glass. In addition, the mould coating has

the effect of retaining moisture and retarding the drying-out process.

3) Fungus may hinder the efficient operation of equipment, even though it has not caused

damage to any material part. Examples of this are soiling in optical equipment, or the

formation of undesirable conducting paths in electrical equipment.

The preferred method for controlling fungus growth is by the selection of fungus inert

materials. Also acceptable is the treatment of potential fungus nutrient materials or by

hermetic sealing. Table 1 lists materials which have a known resistance to fungus growth,

whilst Table 2 lists those materials which are potential fungus nutrients.
Table 1 – List of fungus resistant materials
Acrylics Polycarbonate
Acrylonitile-styrene Polyester
Acrylonitile-vinyl-chloride copolymer Polyester-glass fibre laminate
Asbestos Polyethylene
...

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