How do infrared vein locators work?

Infrared vein locator Remove diamond vein locator crystal vein locator iron vein locator minecraft iron vein locator ore vein locator vein locator Minecraft diamond minecraft vein locator blood vein locator blood vein locator Infrared Vein Locator Machine Nurse Injection Helper Handheld Vein Viewer Portable Infrared Vein Finder Device