A keychain mini-breathalyzer with green, yellow, and red lights to indicate blood alcohol content.

Many of these mini-breathalyzers do not provide an actual number indicating you blood/alcohol content but rather use a system such as a red, green, and yellow light to indicate whether you are safe to drive.  A green light indicates you are safe, a yellow light means you should be cautious and perhaps wait to drive, while a red light means you are over the legal limit.  However, it is important to know the DUI/DWI laws in your state to know the legal limit and to use a number to gauge how close your blood alcohol content is to that legal limit.

There are reports of police officials warning against the use of mini-breathalyzers, indicating that they may provide people with a false sense of security in their ability to drive.  Law enforcement officers often note that drivers may be arrested for driving under the influence despite registering under the legal limit on any type of breathalyzer.

There are some mini breathalyzers that are more reliable and provide a numerical readout for you blood alcohol content, but of course, these will be more expensive. And, as law enforcement officials point out, no breathalyzer guarantees safety from a DUI.

A typical example of a mini keychain breathalyzer is the GTMax Alcohol Tester. This small keychain breathalyzer comes with a stop watch and LED light.