The accuracy of the BreathKey Model g10 is ±.01% BAC at .08% BAC. This means that on average the BAC (blood alcohol content) reading from the BreathKey will be within .01% of your true BAC level, if your true BAC level is .080%.
The accuracy of the BreathKey Models s10 and s100 is ±.02% BAC at .08% BAC. This means that on average the BAC (blood alcohol content) reading from the BreathKey will be within .02% of your true BAC level, if your true BAC level is .08%.
By comparison, the breathalyzers used by law enforcement officials have an accuracy of ±.005% BAC at .080% BAC, according to the standards set by the Department of Transportation.
If a breathalyzer is used shortly after drinking, without waiting at least 20 minutes, the alcohol that remains in your mouth may be blown directly into the detector. It will be read at far higher content level than it would if it had passed through the stomach and intestines, into the bloodstream, and then into your exhaled breath.
Remember that all breathalyzers need to be calibrated on a regular basis to maintain accuracy.
Also remember that the results of any breathalyzer test on their own cannot ensure that it is safe for you to drive. Since everyone varies with how they respond to alcohol, only you can make the determination as to how safe you really are.