Fungus | Muffe

MIL STD 810 G – Test Method 508.6 – Fungus

 

SCOPE

 

Purpose
The purpose of this fungus test is to assess the extent to which materiel will support fungal growth and how any fungal growth may affect performance or use of the materiel. The primary objectives of the fungus test are to determine:
  1. if the materials comprising the materiel, or the assembled combination of same, will support fungal growth, and if so, of what species.
  2. how rapidly fungus will grow on the materiel.
  3. how fungus affects the materiel, its mission, and its safety for use following the growth of fungus on the materiel.
  4. if the materiel can be stored effectively in a field environment.
  5. if there are simple reversal processes, e.g., wiping off fungal growth.
Application
Since microbial deterioration is a function of temperature and humidity, and is an inseparable condition of the hot, humid tropics and the mid-latitudes, consider it in the design of all standard, general-purpose materiel (from paragraph 6.1, reference a). This method is used to determine if fungal growth will occur and, if so, how it may degrade/impact the use of the materiel.
 
NOTES:
  1. This test procedure and the accompanying preparation and post-test analysis involve highly-specialized techniques and potentially-hazardous organisms. Use only technically-qualified personnel (e.g., microbiologists) to perform the test.
  2. Although the basic (documented) resistance of materials to fungal growth (Annex B) is helpful in the design of new materiel, it has shown to be unreliable in determining the fungal susceptibility of complex materials, and the use of testing by analysis is discouraged. The physical structure of combined materials and the possible contamination of resistant materials during manufacture is beyond the purview of analysis, and necessitates laboratory or natural environment tests to verify the resistance of the assembled materials to fungal growth.
Limitations
This test is designed to obtain data on the susceptibility of materiel. This method is not intended for testing of basic materials since various other test procedures, including pure culture, mixed culture, and plate testing are available.

 

TEST PROCESS

 

Preparation for incubation
  • Step 1. Assure the condition of the items to be tested is similar to their condition as delivered by the manufacturer or customer for use, or as otherwise specified. Accomplish any cleaning of the test item at least 72 hours before the beginning of the fungus test to allow for evaporation of volatile materials.
  • Step 2. Install the test item in the chamber or cabinet on suitable fixtures, and remove any covers. (see note and Step 5 below).
  • Step 3. Hold the test item in the test chamber at 30 ±1°C (86 + 2°F) and a RH of at least 90 percent but less than 100 percent for at least four hours immediately before inoculation.
  • Step 4. Inoculate the test item and the cotton fabric chamber control items with the mixed fungus spore suspension by spraying the suspension on the control items and on and into the test item(s) (if not permanently or hermetically sealed) in the form of a fine mist from an atomizer or nebulizer. Ensure personnel with appropriate knowledge of the test item are available to aid in exposing its interior surfaces for inoculation.
NOTE: In spraying the test and control items with composite spore suspension, cover all external and internal surfaces that are exposed during use or maintenance. If the surfaces are non-wetting, spray until drops begin to form on them.
  • Step 5. In order for air to penetrate, replace the covers of the test items without tightening the fasteners.
  • Step 6. Start incubation (paragraph 4.5.2) immediately following the inoculation.
Incubation of the test item
  • Step 1. Except as noted in Step 2 below, incubate the test items at constant temperature and humidity conditions of 30 ±1°C (86 + 2°F) and a relative humidity of at least 90 percent but less than 100 percent for the test duration (28 days, minimum).
  • Step 2. After 7 days, inspect the growth on the control cotton strips to verify the environmental conditions in the chamber are suitable for growth. At this time, verify that at least 90 percent of the surface area of each test strip located at the level of the test item is covered by fungus. If it is not, repeat the entire test with the adjustments of the chamber required to produce conditions suitable for growth. Leave the control strips in the chamber for the duration of the test.
  • Step 3. If the cotton strips show satisfactory fungus growth after 7 days, continue the test for the required period from the time of inoculation as specified in the test plan. If there is no increase in fungus growth on the cotton strips at the end of the test as compared to the 7-day results, the test is invalid (see para 4.3.1).
Inspection
At the end of the incubation period, inspect the test item immediately. If possible, inspect the item within the chamber. If the inspection is conducted outside of the chamber and is not completed in 1 hour, return the test item to the test chamber or to a similar humid environment for a minimum of 2 hours. Except for hermetically sealed materiel, open the test item enclosure and examine both the interior and exterior of the test item. Record the results of the inspection.
Operation/use
(To be conducted only if required.) If operation of the test item is required (e.g., electrical materiel), conduct the operation in the inspection period as specified in paragraph 4.5.3. Ensure personnel with appropriate knowledge of the test item are available to aid in exposing its interior surfaces for inspection and in making operation and use decisions. Disturbance of any fungus growth must be kept to a minimum during the operational checkout. If the test item fails to operate as intended, see paragraph 5, and follow the guidance in paragraph 4.3.2.
WARNING: Because of the potential hazardous nature of this test, operation/use by personnel with appropriate knowledge of the test item will be performed under the guidance of technically-qualified personnel (e.g., microbiologists). Appropriate personal protective equipment (PPE) must be worn.
Decontamination
See Annex A.

 

NOTE: Tailoring is essential. Please, ask to your confidence laboratory for further details about tailoring of test methods.

 

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