GB/T 2423.16-2022Environmental testing - Part 2: Test methods - Test J and guidance: Mould growth (English PDF)

4.1 Background

Under certain climatic and environmental conditions, micro-organisms may settle on

and colonize the surface of electrotechnical equipment. Their presence or their

metabolic products may not only damage the equipment itself, but may also affect the

equipment's operability and serviceability. The actions of micro-organisms on

equipment are influenced by two different processes: direct action in which the

deterioration of material serve as a nutritive substance for the growth of the micro-

organisms and indirect action in which the metabolic products of the micro-organisms

generate deterioration.

The preferred method for controlling the effects of micro-organisms is by the selection

of materials that do not promote growth. Also acceptable is the treatment, or hermetic

sealing, of potentially vulnerable materials and components. Additionally, equipment

may not need to be evaluated if it is stored and/or operated throughout its entire life, in

conditions unlikely to encourage the growth of micro-organisms. Only if these cannot

13.1 Visual examination

The specimens shall be examined (see 13.3), checked and/or photographed (as required

by the relevant specification), immediately after they are removed from the container

or humidity chamber, because the growth can change its appearance by desiccation. See

Annex C, for recommended safety methods of handling.

Following a visual examination and assessment of the actual growth, the mycelium

shall be carefully removed with ethanol 70% vol from the surface which shall then be

examined through a microscope to assess the nature and extent of any attack (e. g.,

etching) on the specimen. See Annex C for recommended safety methods when

removing the mould growth.

13.2 Effect of growth

When the relevant specification calls for electrical and/or mechanical checks while

damp (following incubation), it is essential that the relative humidity of the

surroundings of the specimen(s) shall not be allowed to fall unduly until after such

checks have been made. The checks shall therefore be carried out on small specimens

while still exposed in the container with the lid fitted and free water. For large

specimens checks shall be made while they are still in the humidity chamber.

Note: When electrical connections have to be made or work has to be done on

specimens in containers or humidity chambers with the lids or doors necessarily

opened, this operation should be carried out with regard to the safety of

operators. See Annex C for recommended safety methods of handling.

Requirements of the manufacturer for operation under damp heat conditions

given in the operation manual will be observed.

Similar checks shall be made on the specimens inoculated with spore suspensions and

those inoculated with water only. Any significant difference between the two groups is

considered to be additional due to the presence of mould growth as well as the high

humidity.

Following the checks, the specimens shall be removed and visually examined as

prescribed in 13.1 and finally any attack on the specimen shall be determined.

If the relevant specification prescribes checks after recovery, the specimens shall be

removed from the container or chamber then visually examined as specified in 13.1 and

then exposed to the specified conditions for recovery for a period of 24 h at the

conclusion of which the checks shall be made.

12.3 Extent of growth

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