A North American Class I Railroad conducts training of first responders each year through a program hosted in communities along its rail network by a Safety Train, which is made up of a locomotive, a tank car with fittings for training, and a box car which has been converted into a classroom. This program is used to educate first responders on the commodities that are being shipped through their communities, and is intended to boost the preparedness of first responders should a rail emergency occur. In one case, shortly after training took place in Danville, KY, a rail emergency involving a hazardous chemical occurred in Danville. During the training, mathematical modeling of a chemical release was discussed as a tool used by Occupational and Environmental Health and Safety (OEHS) professionals to determine the potential impacts on a community. Models provide guidance as to the appropriate protective action that should be taken during a release. The local fire chief assumed Incident Command and contacted an OEHS professional to conduct modeling and determine appropriate protective actions. The modeling (performed in real-time in the middle of the night) allowed the Incident Commander to make an informed decision in regards to establishing the location and extent of the Hot Zone, the need for evacuations of residents nearby the release, and the appropriate level of response. Once on scene, OEHS professionals conducted air monitoring, which provided further guidance and resolution to the response – keeping first responders safe from immediate hazards, while using action limits and recommending appropriate PPE to ensure that exposures did not present long-term respiratory hazards.