A breathalyzer (or breathalyser) is a device for
estimating blood alcohol content (BAC) from a breath
sample. "Breathalyzer" is the brand name of
a model made by one manufacturer of these instruments
(originally Smith and Wesson, later National Draeger),
but has become a genericized trademark for all such
instruments. Intoxilyzer, Intoximeter, Alcotest, Alcosensor
and Datamaster are the other most common brand names
in use today.
Breath analyzers don't directly measure blood alcohol
content or concentration, which requires the analysis
of a blood sample. Instead, they estimate BAC indirectly
by measuring the amount of alcohol in one's breath.
Three technologies are in use: evidentiary machines,
used by police forces, which generally utilize infrared
spectrophotometer technology; less accurate hand-held
electrochemical fuel cell-based instruments, used by
officers in the field and commonly called PBT (preliminary
breath test) or PAS (preliminary alcohol screening);
and semiconductor oxide based testers, cheapest and
least reliable but becoming increasingly popular for
personal and professional testing applications.