There is often confusion between product testing in a laboratory and testing carried out during an inspection. While both have a common objective, which is to ensure the quality, safety and conformity of goods, these two types of inspection differ in significant ways.
During each stage of manufacturing, a product must be tested to ensure that it conforms to a diverse set of standards. The tests that are used will depend on what standards the product is being measured against. In general, most of the tests a product is subjected to belong to two broad categories:
Laboratory testing is usually (but not always) used to test whether a product conforms to mandatory standards imposed by the country or region where it is to be sold, such as the USA or the EU.
Meanwhile, product inspection is used to ensure that a product conforms to the manufacturer's specifications, client expectations, and required levels of workmanship.
The following list demonstrates the most significant differences between laboratory testing and product inspection.
Laboratory tests are used to ensure a product's conformity to mandatory specifications or requirements of the country into which that product will be imported. It should be noted that conforming to mandatory tests does not ensure or even imply the quality of the goods.
For example, children's jewellery destined for the USA must conform to mandatory regulations regarding the amount of lead contained in the piece. However, the presence or absence of lead does not ensure that the jewellery will conform to the buyers' quality requirements: for example, whether a clasp functions properly, or a decorative coating is evenly applied.
Product inspections assess the quality of the product at the production facility, to ensure that it is up to the manufacturer's and buyer's requirements. For example, in the case of children's jewellery, a product inspection can check for the correct alignment and colour of the gems in the piece.
Laboratory tests are performed in the controlled environment of a laboratory. The exact conditions under which each test is performed are laid out in the relevant regulatory specification or standard. For example, the standard may require the use of certain equipment, temperatures, chemicals, techniques, timing, etc. to perform the test. All these requirements must be followed precisely in order for the test results to be used to certify the product.
Tests in the scope of a product inspection are carried out at the manufacturing facility. The inspector will have less sophisticated testing equipment available, and will not be able to precisely control the environment. The results of any test carried out under these conditions cannot be used to meet the specifications of a standard.
Laboratory tests tend to take much longer than product inspections, and the items being tested are often destroyed during testing. Furthermore, once conformance to a specification is established, no further testing is required until either a change in production occurs or sufficient time has passed in the production run to necessitate subsequent testing. All of which means that far fewer pieces are needed for laboratory testing.
Product inspection is carried out much more rapidly, onsite and non-destructively, so many more items can be tested. Furthermore, internationally recognized product inspection standards employed by the best inspectors, such as ISO 2859-1, specify that dozens, or even hundreds of items must be tested in each production batch, depending on the test and batch size.
Laboratory tests are often required to last hours or days. This means that they need several days to weeks to complete, and should be scheduled well in advance to ensure they do not hold up production.
By contrast, product inspection is much faster: inspecting an entire batch can be done in a matter of hours, without any interruption to production.
Laboratory tests are generally carried out once during the design and pre-production, and once more during production, to ensure that the products meet the mandatory specifications before mass production is started.
Product inspection, however, is a continuous process that should be carried out at every stage of production, up to and including packaging and loading. Ideally, an inspector is present in the factory every day of the production run, continuously testing conformity of the product.