3. It's important to know that portable equipment implies 'a variable, but fixed (usually), environment', whereas hand-held equipment implies 'any of many environments in which a person will want to take equipment and use it'. These two situations can complicate the success of a product's usefulness and reliability because a developer may not consider 'everywhere' a portable or a hand-held product will be taken. And believe me, a product will be expected to function properly and reliably wherever a person chooses to take it.

To determine this, get feedback from your marketing (and any existing users), sales, production, distribution and repair/maintenance people, as they most likely know about (1) potential environments in which the product may be used and (2) unanticipated uses of the product that you may not have considered. If they have no suggestions, then consider some brainstorming to expand your vision. To help your thinking - following are the main categories of environmental circumstances to which a product should be gauged. Some of the following sources of wear and tear may already be included (specified wear and tear) in your product requirements and some may not. Those that are not (unspecified wear and tear) should be seriously considered to determine whether they should be a part of your specs.

Note that the examples of wear and tear given in each of these categories were never considered during the design and development of the (unnamed) products. In most cases these unspecified wear and tear requirements were later added to the product specifications, and tested for conformance… this after the companies received market complaints or liability claims.