National Academy of Engineering
Greatest Engineering Achievements of 20th Century: Air Conditioning & Refrigerat
Students learn about air conditioning and refrigeration in the 20th century. The resource consists of historical information, a timeline, and a personal essay by a key innovator.
CK-12 Foundation
Ck 12: Physical Science: Heating Systems
[Free Registration/Login may be required to access all resource tools.] Explores the function of a heating system and how it works.