The practice of capping the ends of duct started more than 15 years ago. Over the past several years, there has been a substantial increase in the requirements for covering the ends of duct after fabrication and during transportation, storage and installation. Covering duct prevents dust and debris from accumulating in the duct system and creating a potential source of indoor air quality issues, including mold. Many architects, engineers and inspectors are requiring the practice of covering duct ends prior to arrival at job sites. Rolls of adhesive backed plastic and elastic banded duct covers are now a common tool for sheet metal shop workers and for field installers.