Occupational Health and Safety Assessment Series (OHSAS) Specification 18001. specification process that establishes requirements for a company's occupational health and safety management system. The American Bureau of Shipping's Quality Evaluations group conducted the certification process for NASSCO. The specification was developed to be compatible with ISO 9001 quality certification standards and ISO 14001 environmental management standards, to facilitate the integration of quality, environmental and occupational health and safety management systems at company facilities. Shipping for the company's implementation of the international standards on manufacturing and engineering quality.