This historical 1947 photograph was provided by the Center for Disease Control's (CDC), National Institute for Occupational Safety and Health (NIOSH). It depicted an indoor array of combustion engines that were in the process of being performance tested at the Pacific Car & Foundry Co., Renton, Washington. The exhaust produced by these engines had to be removed through a ventilation system, to which each engine was engaged by way of corregated hoses connecting each engines block manifold to the