Introduction
The ability to easily monitor one’s breath alcohol concentration (BrAC) may be useful in situations where driving a vehicle above a certain limit constitutes a violation of the law. Other potential uses include remote monitoring of alcohol use \cite{Gordon_2017}, self-tracking \cite{Gimpe2013,Lupton_2016}, use in drinking establishments \cite{Lang_1998}, medicine \cite{Gibb1984,Indig2008}, family law \cite{Horra2018}, research \cite{Riordan2017} and workplace testing \cite{Miller2007}.
Scant research exists on the performance of small, inexpensive breath alcohol analyzers marketed for personal use. In 2003, Van Tassel coined the phrase, "pocket model breath tester" (PMBT) to describe such a device and found most of the devices examined to be lacking in analytical performance \cite{edward2003}. More recent examinations of these types of devices have shown mixed results \cite{Ashdown_2014,Delgado_2017,Riordan_2017,erwin2015a,Delgado_2021}.
This study assessed BACtrack®’s line of smartphone-connected breath alcohol analyzers in vitro against known reference standards. The analyzers were evaluated for accuracy, precision, specificity, and measurement uncertainty. Special attention was paid to the measurement uncertainty at the 0.080 g/210L ethanol vapor concentration due to its legal implications in the United States and other countries.