GB/T 2423.16-1999 Environmental testing for electric and electronic products Part 2: Test methods Test J and guidance: Mildew growth
Some standard content:
GB/T2423.16-1999
This standard is equivalent to the international standard IEC68-2-10 "Basic environmental testing procedures Part 2: Test methods Test J and guidance: Mildew growth" (Fifth edition, 1988).
This standard is a revision of GB/T2423.16-1990 "Basic environmental testing procedures for electric and electronic products Test J: Long test method" and GB/T2424.9-1990 "Basic environmental testing procedures for electric and electronic products Mildew growth test guidance". When GB/T2423.16-1990 was formulated, the "Appendix F Guidelines" in the IEC68-2-10 (Fifth Edition, 1988) standard was used as another national standard GB/T2424.9-1990 "Basic Environmental Test Procedures for Electrical and Electronic Products - Guidelines for Mildew Test". In order to completely adopt the IEC international standard and facilitate the use of the GB/T2423.16 standard, this revision will still use the "Appendix F Guidelines" in the IEC68-2-10 standard as Appendix F of this standard, and the GB/T2424.9-1990 standard will be invalidated. At the same time, in order to facilitate the use of this standard in my country, the Appendix F "Test Bacteria Number Comparison Table" of the GB/T2423.16-1990 standard will be changed to this standard. Notes to Table 1 of the standard. From the date of its entry into force, this standard replaces GB/T2423.16-1990 and GB/T2424.9-1990. Appendices A, B, C, D, E and F of this standard are all appendices to the standard. This standard was proposed by the Ministry of Electronics Industry of the People's Republic of China. This standard is under the jurisdiction of the National Technical Committee for Standardization of Environmental Conditions and Environmental Testing for Electrical and Electronic Products. The drafting unit of this standard: the Fifth Research Institute of the Ministry of Electronics Industry. The main drafters of this standard: Zhang Zheng and Wang Zhong. This standard was first issued in 1981, revised for the first time in 1990, and is now revised for the second time. 197
GB/T2423.16—1999
IEC Foreword
1) The formal resolutions or agreements of the International Electrotechnical Commission (IEC) on technical issues are formulated by technical committees attended by representatives of national committees with special concerns about the issue. They express the international consensus on the issue as much as possible. 2) These resolutions or agreements are for international use in the form of standards and are recognized by the national committees in this sense. 3) In order to promote international unification, IEC hopes that all national committees should adopt the contents of IEC standards as their national regulations to the extent permitted by their domestic conditions. Any differences between IEC standards and corresponding national regulations should be clearly pointed out in the national regulations as much as possible.
IEC Foreword
This standard was prepared by IEC Technical Committee 50 (Environmental Test The fifth edition of this standard replaces the fourth edition (1984) of Test J: Mildew Growth. The content of this standard is based on the following documents: June Legal Documents
50B(CO)251
50B(CO)263
Voting Report
50B(CO)257
50B(CO)265
Detailed information on the voting of this standard can be found in the voting report in the table above. 198
National Standard of the People's Republic of China
Environmental Testing for Electrical and Electronic Products
Part 2: Test Methods
Test J and Guide: Mildew Growth
Environmental testing
for electric and electronic products-Part 2:Test methods---Test J and guidance : Mould growth1General
GB/T 2423.16—1999
idt IEC 68-2-10:1988
Replaces GB/T2423.16-1990 and
GB/T 2424.9—1990
1.1This test uses the method of inoculating the assembled samples with selected mold spores and then culturing them for a period of time under conditions that promote spore germination and mold growth to carry out mold growth tests. This test provides two different test methods. Test method 1 stipulates that the samples are inoculated directly with mold spores; test method 2 stipulates that the samples are inoculated after pre-treating the samples with a nutrient solution that can support the growth of bacteria. 1.2 This test procedure may be used to assess the extent of fungal growth and/or the resulting degradation of performance when assembled specimens must be exposed to airborne mold spores and when operating in locations where climatic conditions favor mold growth. 1.3 It is recommended that other established fungal test procedures be used to assess the susceptibility of structural materials to mold contamination and that only materials not seriously attacked by mold be used.
1.4 This test procedure is also applicable to assembled specimens that do not have to be exposed to mold spores during operation but may have to be temporarily exposed to mold spores during storage or transportation.
1.5 When assembled specimens are exposed to the atmosphere during storage, use, or transportation or are unprotected during handling, surface contamination from dust, stains, condensed volatile nutrients, or grease may be deposited on the specimens. This surface contamination may result in increased mold implantation and may cause additional mold growth and damage. The effects of this contamination may be assessed using Test Method 2. 1.6 The ability of the specimen to withstand the rigors of this test is not necessary if the assembled specimen is protected from exposure to mold spores, even when operated in an area where mold spores are abundant. 1.7 Because of the difficulty in maintaining the necessary test conditions in a large test chamber, large assembly equipment is usually tested in subassemblies. Overall, this minimizes the cost of testing because several subassemblies may be so similar in construction that only one need be tested.
2 Hazards to Operator Health
2.1 This test procedure requires the use of live mold spores and the provision of environmental conditions that promote the growth of fungi. 2.2 Before commencing contact with fungal species or conducting the following test procedures, the operator should first study the appendices of this standard. Reference: Appendix A - Hazards to Operators Appendix B - Inoculation Method
Appendix C - Recommended Safety Precautions
Appendix D - Decontamination Methods
Approved by the State Administration of Quality and Technical Supervision on September 13, 1999 and implemented on June 1, 2000
3 Purpose
GB/T2423.16-1999
The purpose of this test is to find the cause of unforeseen deterioration of assembled samples by using test method 1 and/or test method 2 with a specified severity level in the relevant specifications, whether the assembled samples are made of mold-resistant materials or not. a) Test method 1: Evaluate the degree of mold growth and any resulting physical damage after 28 days of incubation; if required by the relevant specifications, check the effect on sample performance after the incubation time is extended to 84 days. b) Test method 2: Pre-treat the samples with nutrient solution, and evaluate the degree of mold growth and any resulting physical damage after 28 days of incubation, and check the effect on sample performance. The relevant specification shall specify the test method and severity level selected. 4 Reagents and materials
4.1 Bacteria or spores - Supply and conditions
4.1.1 The bacteria listed in Table 1 shall be used for this test. The expected aggressiveness of each bacteria is listed as a reference. Regardless of the nature of the sample, all bacteria spores shall be mixed together. The research center that provides bacteria or spores for this test shall certify that the materials provided meet the requirements of this standard. Table 1 Test strains and their aggressiveness Aspergillus niger Aspergillus terreus Aureobasidium pullulans Paecilomyces varioti Penicillium funiculosum Penicillium ochrochloron Scopulariopsis brevicaulis Trichoderma viride Strain nomenclature V. Tieghem
(De Barry)
Arnaud
Bainier
Biourge
(Sacc.)Bain
Var. Glabra Thom.
Pers.Ex.Fr
Typical strains (for reference only)
ATCC,6275
PQMD,82j
ATCC,9348
IAM,5001
1AM,7013
ATCC,9112
IAM,5146
IAM,5061
Grows in large quantities on many materials, resistant to copperbZxz.net
salts
Attacks plastics
Attacks paint and wax paint
Attacks plastics and leather
Attacks many materials, especially textiles Fabrics
Resistant to copper salts, corrodes plastics and
Textiles
Corrodes rubber
Corrodes fabrics and plastics
Note 2, the corresponding strain protection number of the Chinese Institute of Microbiology for each strain: Aspergillus niger AS3.3928, Aspergillus terreus AS3.3935, Budding short stalk mold AS3.3984, Paecilomyces variotii AS3.4253, Penicillium funiculosum AS3.3875, Ochroderma ochraceus AS3.4302, Light spore short handle emperor AS3.3985, Green Trichoderma AS3.2942
4.1.2 The strains from the recognized fungal research center should be placed in appropriate containers and the inoculation date should be marked on them. 4.1.3 The strains and freeze-dried spores should be handled and stored according to the supplier's recommendations. The user should mark the inoculation date of the strain prepared from the freeze-dried spores on the inoculation container.
Instructions for use:
1] Since the reference strain number given in the IEC standard is the typical strain number of the United States and the strain number of the Institute of Microbiology, University of Tokyo, Japan, which cannot be obtained in China, this test can use domestic strains according to the Chinese strain number. The strains in the IEC standard are equally effective as the domestic strains. 2] The strain numbers used are based on the strain numbers in the Chinese strain catalog compiled by the China Microbiological Culture Collection Administration in 1992. 200
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4.1.4 The strains used to prepare the spore suspension should be stored at room temperature for not less than 14 days but not more than 28 days from the inoculation date marked on the inoculation container.
4.1.5 If the strain is not used immediately, it should be stored in a refrigerator at 5℃～10℃, and the continuous storage time should not exceed six weeks. The culture medium used for preservation shall be cultured for not less than 14 days but not more than 28 days after inoculation, calculated from the inoculation date marked on the inoculation container, and then preserved. 4.1.6 The stopper of the container containing the culture medium shall not be removed before preparing the mold spore suspension. Only one spore suspension shall be prepared from an opened culture medium container. Each batch of prepared spore suspension shall be contained in another container. Note: The recommended safe method for carrying out the following test procedures is shown in Appendix C. 4.2 Preparation of mold spore suspension
4.2.1 The spore suspension shall be prepared using distilled water with 0.05% wetting agent added. N-methyltaurine or dioctyl sodium sulphosuccinate can be used as the wetting agent. The wetting agent shall not contain substances that support or inhibit the growth of the fungus.
4.2.2 Slowly add 10 mL of water containing a wetting agent to each bacterial tube. Heat the root inoculated platinum or nickel-chromium wire over a flame until it is red to sterilize and cool, then use this wire to gently scrape the surface of the culture to release the spores. Shake the liquid slightly to disperse the spores without separating the mycelial fragments, and then slowly pour the spore suspension into the conical flask, and use this conical flask to collect all other spore suspensions. 4.2.3 Shake the conical flask vigorously to thoroughly mix the eight spore extracts and disperse the spores that have clumped. The spore suspension should be allowed to stand for at least 30 minutes, and then filter through a good quality fiber filter paper with a fast filtration rate to remove mycelial fragments, agar blocks and spore clumps. 4.2.4 Centrifuge the filtered spore suspension and remove the supernatant. Resuspend the precipitate with 50 mL of distilled water and centrifuge again. Wash the spores three times in this way, and then dilute the final precipitate as follows. 4.2.4.1 For test method 1: dilute the final precipitate with 100 mL of distilled water. 4.2.4.2 For Test Method 2: When the sample is pretreated with a nutrient solution prior to spray inoculation as described in Chapter 8, the final sediment shall be diluted with 100 mL of distilled water. When the sample is inoculated by coating or dipping, the nutrient solution given in 4.3.2 may be used in place of distilled water to prepare the suspension.
If the nutrient solution of the spore suspension is used for inoculation, the pretreatment procedure given in Chapter 8 shall be omitted. 4.2.5 The spore suspension may be diluted with distilled water or nutrient solution to a maximum volume of 500 mL and shall be used on the day it is prepared. 4.3 Control Strips
4.3.1 The control strips required for this test shall be made of strips of pure white filter paper or non-waterproof cotton cloth. 4.3.2 The nutrient solution used to prepare the control strips shall consist of a solution of the following reagents in distilled water and shall be used on the day it is prepared. The following reagent amounts are per liter of distilled water.
Potassium dihydrogen phosphate (KH,PO)
Potassium dihydrogen phosphate (K,HPO,)
Magnesium sulfate (MgSO4·7H,0)
Sodium nitrate (NaNO:)
Potassium chloride (KCI)
Ferrous sulfate (FeSO.·7H2O)
4.3.3 The control strips should be placed in a small container and soaked in nutrient solution. The control strips should be removed from the nutrient solution and dripped dry before use. 4.3.4 Fresh control strips should be prepared on the day of the test. 5 Test equipment requirements
5.1 Equipment for small samples
5.1.1 Glass or plastic containers with tight lids that can hold samples should be used. The size and shape of the container should be sufficient to have a water surface area exposed at the bottom of its internal space to maintain the relative humidity in the container greater than 90%. The sample should be placed in a way that ensures that the sample is not touched or splashed by water. 201
GB/T2423.16--1999
5.1.2 For test chambers used to incubate small samples placed in containers, the temperature of the entire working space in the chamber shall be uniformly maintained within the range of 28°C to 30°C. The temperature cycle caused by the operation of the thermostat shall not exceed 1°C/h. 5.2 Equipment for large samples
5.2.1 Suitable humid chambers shall be used to incubate large samples that are too large to fit into the containers specified in 5.1.1. The humid chamber shall have a well-sealed door to prevent air exchange between the chamber and the test room. 5.2.2 The relative humidity in the humid chamber shall be maintained above 90%, and condensation shall not be allowed to drip onto the samples from the chamber walls or roof. The temperature of the entire working space in the chamber shall be uniformly maintained within the range of 28°C to 30°C. The temperature cycle caused by the operation of the thermostat shall not exceed 1°C/h.
In order to make the temperature and humidity in the whole box uniform, the air circulation can be forced in the box, and the air flow rate on the sample surface should not exceed 1m/s.
6 Severity level
The test severity level of each test method is determined by the duration of the test. Test method 1: Two severity levels are specified: 28d and 84d. Test method 2: One severity level is specified: 28d. The relevant specifications should clearly specify the test method selected for this test and the required severity level. 7 Initial inspection
Before the test, the test sample should be visually inspected and the electrical and mechanical properties should be tested according to the requirements of the relevant specifications. 8 Pretreatment
8.1 For test methods 1 and 2
The samples used for the test should be in the state when the user receives them from the manufacturer for use. The samples should not normally be cleaned, but if the relevant specifications specify, it is allowed to clean half of the sample with ethanol or water containing detergent before the test, and then rinse with clean water. This method can distinguish between mold growth caused by the use of inappropriate materials in the sample structure and surface contamination. Note: Class 0 (see 10.3)
When the relevant specification requires a long-term class of 0, it is advisable to consider cleaning the sample before testing, because possible contamination may promote mold growth in test method 1.
8.2 For test method 2
The test sample inoculated with spore suspension is first pretreated with a nutrient solution. The composition of the nutrient solution is shown in 4.3.2, and 0.05% non-bactericidal wetting agent is added. The nutrient solution can be sprayed, coated or diffused on the sample, or pretreated as specified in the relevant specification (see 4.2.4.2). Samples treated with nutrient solution should be dried before inoculation. 9 Conditioning test
9.1 Application
9.1.1 For the test methods specified in the relevant specifications, they should be applied as specified below. 9.1.2 Test Method 1
If the relevant specification requires testing after 84 days of testing, two groups of samples should be prepared; one group is inoculated with mold spores and then cultured (test samples); the other group should be exposed to moist conditions, not inoculated, and then cultured (see 9.2). The latter samples are called "negative control samples".
Test Method 2
It should contain two groups of samples. One group, the test samples, should be inoculated with mold spores after pretreatment with nutrient solution and then cultured for 28 days, and the other group should not be pretreated with nutrient solution, not inoculated, exposed to moist conditions, and then cultured for 28 days. The latter samples are called "negative control samples"202
Note: Negative control samples
GB/T 2423.16-—1999
Negative control samples should be placed in a separate test box from the inoculated samples and exposed to the specified conditions. In order to ensure that mold does not grow on the negative control samples, the box should be sterilized by one of the methods given in Appendix D D2. If the negative control does not support mold growth, the test is valid. 9.2 Inoculation
Depending on the size and nature of the specimen, the test specimen and control strips shall be inoculated with a spore suspension (see 4.2) by spraying, coating or flooding (see Annexes B and C).
The negative control shall be sprayed, coated or immersed in distilled water and protected from contamination. 9.3 Incubation
9.3.1 Inoculate within 15 min as described in 9.2. Small test specimens shall be grouped into groups, each containing three control strips that can be placed in a container (see 5.1.1). The specimens and control strips shall be well spaced. The container shall be placed in an incubator (see 5.1.2). 9.3.2 The negative control specimen shall be placed in a container similar to the test specimen but separate from the inoculated control strip, which shall then be placed in an incubator (see 5.1.2).
9.3.3 For large test specimens, the three control strips shall be placed in a humid chamber with the specimen. The negative control sample is preferably placed in a separate humid chamber. If the same chamber is used, the negative control sample should be placed immediately after the mold test is completed and decontaminated (see Appendix D). 9.3.4 The container lid should not be opened or otherwise disturbed except for checking the control strips during the first 7 days to determine the vitality of the inoculum and a few minutes of oxygen replenishment. This operation is repeated every 7 days until the specified test time is completed. 9.3.5 If no mold growth is visible to the naked eye on any of the control strips when the strips are opened for inspection for the first time 7 days after inoculation, the test should be considered invalid and the test should be repeated. 10 Final inspection
10.1 Visual inspection
10.1.1 After the sample is removed, it should be inspected (see 10.3) and (or) photographed (as required by relevant specifications) immediately, because once the sample is exposed to the dry air in the test room, the appearance of all mold growth will change rapidly. See Appendix C for recommended safe operating methods. 10.1.2 After the sample has been visually inspected and the actual growth of mold has been assessed, the surface hyphae should be carefully washed away and then examined under a microscope to assess the nature and extent of physical damage (e.g. etching) to the sample. See Appendix C for recommended safe cleaning methods. 10.2 Effects of mold growth
10.2.1 When the relevant specification requires electrical and/or mechanical property tests to be carried out in a humid state (after incubation), the relative humidity around the sample should not be allowed to drop excessively before the test is completed. Therefore, the test of small samples should still be carried out in a covered container with the water surface exposed; the test of large samples should still be carried out in a humid cabinet. Note: When electrical connections are to be made, or when it is necessary to open the lid of the container or the door of the humid cabinet to work on the sample, such operations should be carried out under conditions that appropriately consider the safety of the operator. See Appendix C for recommended safe operating methods. 10.2.2 When the relevant specification requires testing after the sample has recovered, the sample shall be removed from the container or box, visually inspected as specified in 10.1.1, and then exposed to the specified conditions for recovery for 24 hours. After recovery, the performance test shall be performed. 10.2.3 The same test shall be performed on the samples inoculated with the spore suspension and the samples inoculated with distilled water only. Any significant difference between the two groups of samples is considered to be due to mold growth and the addition of high humidity. 10.2.4 After testing, the sample shall be removed and visually inspected as specified in 10.1.1, and finally the physical damage suffered by the sample shall be determined in accordance with 10.1.2. 10.3 Extent of mold growth
The tested samples shall first be examined by the naked eye and, if necessary, by a stereo microscope (nominal magnification of approximately 50 times). The degree of mold growth should be evaluated and expressed according to the following grades: 0 - no obvious mold growth at a nominal magnification of about 50 times; mold growth is not visible or difficult to see with the naked eye, but it is obvious under a microscope; 1--
2--Mold growth is obviously visible to the naked eye, but the coverage area of the sample surface is less than 25%; 3--Mold growth is obviously visible to the naked eye, and the coverage area of the sample surface is greater than 25%. 203
GB/T2423.16-—1999
Note: When the sample includes an assembly showing different degrees of growth, they should be evaluated separately. For test method 2, level 0 should be specified only when the sample is required to check the effectiveness of the antifungal agent. 11. Explanations to be given in the relevant specifications
When the relevant specifications adopt this test, the following details should be given: a) Test methods 1 and 2
b) Severity level: Test duration
c) Electrical and mechanical performance testing before conditioning test (only when performance degradation needs to be determined) d) Pretreatment
e) Conditioning test
f) Electrical and mechanical performance testing after test (only when performance degradation needs to be determined)) Whether the sample must be inspected, tested and/or photographed h) After the test Whether electrical and mechanical tests are required, and if so, whether they are carried out in a wet state or after recovery, or in both cases i) Tests after recovery
Chapter number
10.1,10.2,10.3
A1 General
GB/T2423.16--1999
Appendix A
(Annex to the standard)
Hazards to operators
A1.1 From the point of view of mycologists and pathologists, performing mold growth tests poses a health hazard unless special precautions are taken. A1.2 The precautions detailed in the appendix are based on established microbiological techniques and dedicated equipment, and it is recommended that test personnel be trained in the use of these techniques and equipment.
A1.3 It is recommended that a separate dedicated room be provided for mold growth tests. A1.4 It is recommended that a microbiological safety cabinet (MSC) be used to perform certain parts of the test procedure, including the examination of strains obtained from the supply source.
A1.5 Airborne toxic fungal spores often enter the human body through the nose and mouth, but usually do not pose a serious health hazard. However, some sensitive people may be affected by repeated inhalation of certain spores (including the spores of the fungus used in this test). Therefore, precautions outlined in Appendix C should be taken when conducting this test.
During the incubation period in the test chamber, foreign molds may become unintentional invaders and grow. When some of these molds become local bacteria in certain test areas, they may invade the human system. A1.6 It is recommended that all persons who intend to be involved in this test inform medical personnel or their own doctors of the work they are engaged in and receive medical approval or disapproval.
A1.7 All persons conducting this test should be informed of the potential hazards to their current health status, and the units conducting this test should implement national labor protection regulations.
A2 Instructions for medical personnel
A2.1 This test involves the dangers of inhalation, swallowing, and penetration through wounds of airborne mold spores. A2.2 Appendix C gives the safety precautions that should be taken to minimize this risk. A2.3 Special risks exist for sensitive persons, such as a) those with atopic sensitivity, usually to pollen, house dust, animal dander, etc., who suffer from nasal catarrh, asthma or other hypersensitivity. The risk for these persons is that they may develop a type 1 allergic reaction to mold spores, but in certain environments may develop a direct reaction (agro-lung type).
b) Patients with chronic lung diseases, such as those with bronchitis, chronic bronchitis, sarcoidosis, emphysema, etc. The deposition and germination of spores in the lung cavity may lead to the growth of fungi, forming fungal balls or aspergilloma, mainly related to fumitrin. Healed tuberculosis lesions may become sites for mold growth. c) Patients currently receiving broad-spectrum antibiotic treatment, taking immunosuppressive drugs including corticosteroids, or taking other prescribed chemotherapy agents. Due to the elimination of the normal bacterial flora of the respiratory and digestive tracts, it is sometimes possible to allow extensive fungal growth, and immunosuppression may make individuals more susceptible to fungal infections.
Although the risk involved in the test is considered low when the test is carried out according to the prescribed procedures, it is recommended that the above types of personnel should not be involved in this test.
GB/T2423.16—1999
Appendix B
(Standard Appendix)
Inoculation method (see Chapter 9)
B1 Before starting the inoculation, you should study Appendix C "Recommended safety precautions". B1.1 The generally suitable inoculation method is to spray the mold spore suspension onto the sample and control strips. The spray gun used should have a nozzle large enough to avoid clogging by mycelium fragments. It has been found that the type of spray gun known as "artist's spray gun" is more suitable. The container and nozzle should be sterilized before each use.
B1.2 If the sample has a hard and polished surface, the sprayed spores may not adhere to it easily. At this time, it may be more effective to use a sterilized soft-bristled brush to apply the mold spore suspension. B1.3 For small samples, dipping them in a suspension of mold spores is a quick and effective method. B2 It is recommended that all inoculation methods be performed in a MSC, otherwise the spore suspension may form an aerosol in the air. B3 For large samples, the components should be disassembled as described in 1.7 if possible. However, if the sample is still too large to be inoculated in the MSC, consider installing a temporary exhaust hood over the sample, which should have the same or approximately the same airflow conditions as the microbial exhaust system specified in the MSC.
Another method is to place the large sample directly into the humid chamber, apply the spore suspension inoculation, and then incubate in the humid chamber. Any droplets should be wiped off with ethanol as described in Appendix D. Although this method may not produce an airborne aerosol, if the recommended exhaust system is installed on the humid chamber, the exhaust system should be turned on during inoculation. Appendix C
(Standard Appendix)
Recommended Safety Precautions
C1 Safety precautions should be taken to minimize the degree of inhalation and skin contact (especially around the fingernails) of mold spores by operators.
C2 Mold spores may be inhaled when moving or checking samples and control strips after culture, or when the surrounding air is disturbed by opening and closing the test chamber door and container lid. When the growing mold dries, the detached mold particles will be more easily dispersed in the air, resulting in increased danger. When the mold is inoculated on the sample by spraying, the risk of inhalation will also be greater. C3 An approved respirator with a dust filter can be worn to directly prevent the inhalation of mold spores (diameter 1μum~10um) in the air. Gauze or loose masks do not provide adequate protection. However, the best method is to use a microbiological safety cabinet (MSC). C4 To minimize the risk of mold contact with the skin, protective gloves may be worn when handling all strains, inoculated solutions, and test samples after inoculation and incubation. Protective gloves may be made of disposable plastic or sterilizable rubber. Gloves should be wiped and washed with ethanol after use to remove contamination.
C5 All operations including opening mold culture containers, preparing mold spore suspensions, inoculating samples and control strips, and inspecting and testing samples after incubation should be carried out in a microbiological safety cabinet (MSC), and the following precautions should be taken to reduce the formation of airborne suspensions:
a) When preparing mold spore suspensions, use the specified wetting agent (see 4.2.1); b) Before removing the culture container from the MSC and transferring it to the dry heat box for incubation, wipe the outer surface of the culture container with 70% ethanol; c) After the test, when the sample is still in the MSC, wipe or wash the sample with 70% ethanol. This is to remove mold growing on the surface before final decontamination and disposal of the sample. C6 When the sample is too large for a single container and must be incubated in a humid chamber, mold spores may be spread into the air due to air disturbance when the chamber door is closed or opened for inspection of samples or other purposes. Therefore, a suitable exhaust 206
system may be installed on the test humid chamber to prevent mold spore particles from escaping. GB/T2423.16—1999
The exhaust system should exhaust air to the outside atmosphere through a microbial filter. The filter should be checked before the test begins to ensure that the filter is clean and sterile.
C7 If it is necessary to use a large walk-in incubator, protective clothing and a complete hood with a respirator as specified in C3 above or with a suitable air supply duct should be worn. It must be emphasized that particle filters cannot protect against fumigant vapors or fumes. CB If it is necessary to transfer samples from one MSC to another, appropriate precautions must be taken to protect the operator. C9 All test chambers and equipment used for mold growth tests should be decontaminated as soon as possible after use in accordance with Appendix D. C10 At the end of the test, the samples and control strips may have a large amount of mold growth on them and should be handled with care. Destruction by combustion is not recommended because most incinerators cannot achieve complete combustion and the smoke produced can carry spores to a wide area. The control strips should be poured into a container filled with sodium hypochlorite solution (see Appendix D) before final disposal. Samples and gloves that may be discarded, retained or used should be treated according to C5 c) before final decontamination by one of the methods selected from Appendix D. C11 If there is any doubt about the cleanliness of the test chamber and equipment, and if more than 28 days have passed since the previous decontamination, it is recommended that they be decontaminated before starting the test.
C12 Smoking and eating should not be allowed in the test area. Appendix D
(Standard Appendix)
Decontamination Methods
D1 The humid chambers and containers used for the growth of cultured bacteria may be contaminated by test molds and invading molds from outside, so decontamination procedures are necessary. The procedure should be effective for both the test bacteria and the invading bacteria; it should not leave residues of the decontamination agent, which are likely to interfere with the growth of the inoculated mold during the test, and the risk to the user must be minimized. D2 recommends the following decontamination methods:
a) Sodium hypochlorite solution immersion or cleaning: Sodium hypochlorite should be dissolved in water to make a solution (containing 500×10-6 to 1000×10-' of available chlorine). The contaminated test chamber, container or instrument should be scrubbed or immersed in the solution, and ensure that the solution penetrates into all gaps for not less than 30 minutes, and then rinsed thoroughly with clean water.
Sodium hypochlorite has a strong bleaching effect, so the use of this substance for decontamination may not be suitable for some materials. b) High-pressure steam sterilization:
This method is suitable for smaller items that are resistant to high temperatures. The high-pressure steam sterilizer should be set at a pressure of 100kPall (1bar) and a temperature of 121℃,Time 30min.
c) Wipe with ethanol:
Ethanol is diluted with water, the ratio is 70% ethanol and 30% water. Use a clean cloth soaked in 70% ethanol solution to wipe the surface where the mold spore suspension may drip, splash or spray. D3 Before discarding contaminated materials, remaining strains, spore suspensions, etc., use the above method a) or b) to remove contamination. D4 Formaldehyde vapor is an effective decontamination agent, but it is difficult to remove its residues, and it will cause more formaldehyde vapor in a warm and closed space, which may inhibit the growth of test molds. Other volatile fungicides are also effective, but there may be explosion and (or) poisoning problems that affect safety, especially in large test chambers.
Therefore, formaldehyde and other volatile fungicides should be avoided. Instructions for use:
1] The original text here is 10kPa, because 1bar should be 100kPa. The original text is incorrect and is corrected here. 207
If specified
Test method 1
Initial inspection
If specified
Negative control
Open, check
If there is no mold on the control strip
Final inspection
If there are bacteria on both strips
Cleaning, checking
Physical damage
Semi-clean
Control strip
GB/T 2423. 16—1999
Appendix E
(Subject Appendix)
Flowchart
Water spray
Final check
Test force method 2
Initial check
If specified
Negative control
Pretreatment
Open, check
If on control strip
Final check
If both
have mold
Cleaning, check
Physical damage
Semi-cleaning
Control strip
Test chamber sterilization
Water spray
Final check
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