In January 2006, the National Institute for Occupational Safety and Health (NIOSH) released a final Health Hazard Evaluation Report on its investigation at a microwave popcorn production facility. Several employees from this facility were diagnosed with bronchiolitis obliterans, a severe obstructive lung disease. Following this investigation and the evaluation of lung function tests and air sampling results, NIOSH determined that inhalation exposure to butter-flavoring chemicals presents a risk for occupational lung disease. In April 2007, the Centers for Disease Control and Prevention (CDC) reported in its Morbidity and Mortality Weekly Report (MMWR) seven additional cases of bronchiolitis obliterans in employees working in facilities where flavorings were manufactured. This instruction establishes an NEP to identify and reduce or eliminate hazards associated with employee exposure to flavoring chemicals in facilities that manufacture food flavorings containing diacetyl. Diacetyl is one of the most common compounds found during investigations of microwave popcorn and flavoring manufacturing facilities. This NEP provides guidance on targeting, inspection procedures, engineering controls, work practice controls, and compliance assistance.