From publisher blurb:
The Special Supplement series is an expansion of the basic Cepheus Engine rules that allow Referees to better represent the true differences of aliens. This is the first book in a series that will address how to accommodate aliens into the basic ship design process presented by the Cepheus Engine SRD and Cepheus Light. Special Supplement 1: Alien Accommodations deals with how to modify existing components to address aliens aboard. Stateroom size is the most obvious thing that might need to change but there are several other components that also need to be modified to deal with aliens. For the purposes of this book, and this series, we will not be specifying or assuming any particular type of alien; although being able to breathe the same approximate air mixture as humans is a common assumption.