Standards and certifications comprise a vast number of companies and compliances that serve specific purposes—primarily addressing safety, environmental impact, energy efficiency, and sanitation. They are divided into categories for each product type and certification type to allow for very specific qualifications related to each product. When this system is being used as intended, it gives consumers, installers, suppliers, and anyone else who may be involved confidence that the product is safe and will work well in their application. UL and ETL certifications relate to safety and installation and are the most common for power supplies.