Although environmental analysis, design analysis, and laboratory testing are valuable tools in the materiel acquisition process, there are inherent limitations in analysis and laboratory testing techniques that must be recognized. The methods in Part Two of this Standard do not include many of the naturally-occurring forcing functions that may affect materiel performance or integrity in service use. Further, analytic and laboratory test methods are limited in their abilities to simulate synergistic or antagonistic stress combinations, dynamic (time sequence) stress applications, aging, and other potentially significant stress combinations present in natural field/fleet service environments. Use caution when defining and extrapolating analyses, test criteria, and results. Part Two test methods purposely do not address the following but may, in some cases, be applied:
- a. Electromagnetic interference (EMI).
- b. Lightning and magnetic effects.
- c. Nuclear, biological, chemical weapons or their effects.
- d. Certain aspects of munitions and pyrotechnics safety testing.
- e. Piece parts such as bolts, wires, transistors and integrated circuits.
- f. Packaging performance or design.
- g. Suitability of clothing or fabric items that are described in specific specifications.
- h. Environmental stress screening (ESS) methods and procedures.
- i. Reliability testing.
- j. Safety testing.
- k. Space – region beyond Earth’s atmosphere
1.3.1
The climatic data included in this Part apply to essentially all areas of potential use for materiel in all parts of the world except the Antarctic continent (excluded by treaty). These data represent free air (ambient) conditions, and are not to be confused with the response of materiel, either to these conditions, or to those of a platform on or within which the materiel may be located. The selection of climatic environments for testing should be that which gives satisfactory results most economically, considering the extent of deployment in each area of potential use, the current technology level, and the time required for development. For example, if certain materiel is to be used only in areas where cold conditions prevail, materiel should be designed solely for the conditions of those areas. The guidance for following realistic natural environments is provided as a basis for developing design requirements and determining appropriate test conditions:
- a. Climate (temperature, humidity, solar radiation, rain, snow, wind, blowing sand, dust and snow, icing phenomena, ozone, freeze-thaw occurrences, fog, cloud ceiling heights, and visibility).
- b. Weather-related atmospheric obscurants (rain, snow, fog, cloud cover).
- c. Induced climatic conditions (storage and transit).
1.3.2
The general climatic design values in paragraphs 3 and 4 and their sub-paragraphs represent a conservative design approach; i.e., there is little risk that the climatic design values will be exceeded in the areas to which they apply. Because there is some risk, the design values should be modified for some materiel items. In certain cases, failure of an item may be so critical that more severe climatic criteria should be applied to ensure against environment- related failure. In other cases, the consequences of failure may be slight, so the cost of designing to the given values may be unwarranted. Special study may be required in these cases to determine the most appropriate design values. The type of failure is also an important consideration. Two categories of failure that may cause different design decisions are identified as follows:
MIL-STD-810H
PART THREE
- a. Reversible failure. For the duration of climatic extremes, the materiel may continue to function, but its performance or safety is reduced, or it may cease to function. When the extreme climatic conditions cease, the materiel will return to normal operation.
- b. Irreversible failure. The materiel suffers a failure during climatic stress that is so damaging that it will not return to normal operation when the extreme climatic conditions cease.