What is the purpose of the blood alcohol keychain?

The blood alcohol keychain is designed to measure the alcohol content in a person's breath to determine whether they're above or below the legal driving limit. It functions as a portable breathalyzer that provides users with a quick indication of their blood alcohol level, potentially helping them make safer decisions about driving after consuming alcohol. The device is compact enough to be carried as a keychain, making it accessible for use in various social situations where alcohol might be consumed.