What should you inspect for? I can’t answer that. Both the image and this link go to a map of Oregon with county-by-county expected radon levels. The Oregon Real Estate Agency publishes the Oregon Property Buyer Advisory. It oultines issues that buyers can inspect for one of the items is radon. What is radon? According to the EPA:

Radon is a cancer-causing natural radioactive gas that you can’t see, smell or taste. Its presence in your home can pose a danger to your family’s health. Radon is the leading cause of lung cancer among non-smokers. Radon is the second leading cause of lung cancer in America and claims about 20,000 lives annually.

The EPA website includes a lot of information on radon. The site includes a page titled “Home Buyer’s and Seller’s Guide to Radon.” There are links to each topic on that page or you can download the entire pamphlet here as a pdf (or here in Spanish).