Field testing, otherwise known as outdoor exposure testing, is used to assess expected commercial performance of exterior paints and coatings applied to houses and commercial structures. This type of long-term testing has proven to be the best indicator of performance in real-world applications. Laboratory evaluations are beneficial in preliminary stages of product development as a screening tool. However, while laboratory evaluations are faster and less costly, they have considerable limitations. Laboratory evaluations do not account for numerous variables such as the nature and condition of the substrate, microorganisms encountered in actual use, or time frame – in other words, the life of the applied coating. Additionally, when using laboratory testing it is difficult to simulate the migration and depletion patterns that occur in actual use. As a result, outdoor exposure testing is a necessary element in the evaluation of dry-film preservative efficacy in exterior paints and coatings.