An evidential breath alcohol tester is defined as being listed on the DOT Conforming Products List of Evidential Breath Measurement Devices. The National Highway Transportation Safety Administration (NHTSA) evaluates breath alcohol testers to determine if they meet their standards of accuracy, which is +/- 5%.
There are very specific rules that each law enforcement agency must follow when testing for drunk driving, and these rules specify the brands of breath alcohol testers which may be used and the protocol for performing the test. However, these rules apply only to law enforcement agencies and only when testing for drunk driving. Therefore, an agency or a company does not need to use the same brand of breath alcohol testers as their police department for evidential testing. And if they follow the guidelines for evidential quality testing, they can expect to successfully defend their test results.