This educator guide is organized into seven chapters: (1) Overview; (2) The Design Challenge; (3) Connections to National Curriculum Standards; (4) Preparing to Teach; (5) Classroom Sessions; (6) Opportunities for Extension; and (7) Teacher Resources. Chapter 1 provides information about Environmental Control and Life Support Systems used on NASA spacecraft. Chapter 2 provides a brief description of the challenge, time requirements, and materials and cost estimates. A more detailed list of materials appears in chapter 4. Chapter 3 provides correlations to the National Science Education Standards, the Standards for School Mathematics, and the Standards for Technological Literacy. Chapter 4 contains all of the basic information you need to know, and lists everything you need to do, before using the challenge in your classroom. Chapter 5 provides information that will guide you through each session. Chapter 6 describes optional activities that are related to the basic challenge. These extensions are described but not actually developed for you. Chapter 7 contains a list of useful websites, information regarding NASA's Educator Resource Center Network, and black line masters for classroom use. This educator guide has been set up to help you find things quickly and to minimize your need to "jump around." A glossary is included. (Contains 6 tables.)