Theory And Design Of The Alco-Sensor Fst; Fuel Cell Diagram - Intoximeters Alco-Sensor FST Operator's Manual

ALCO-SENSOR FST

Theory and Design of the Alco-Sensor FST

The Alco-Sensor FST contains a fuel cell sensor and an electrically operated piston-sampling pump. The fuel cell is a
porous disk coated with a thin layer of platinum black on both faces and saturated with an electrolyte. The cell is supported
at its outer edge in the fuel cell case. While a subject is blowing and when deep lung breath is reached the sampling pump
is activated. A small, fixed volume of deep lung breath is drawn onto the surface of the cell, any alcohol is subsequently
converted to acetic acid, electrons are released and a current is generated in proportion to the amount of alcohol oxidized.
The resulting electric current is translated into a Breath or Blood alcohol concentration and the result is displayed on the
Alco-Sensor FST.
If there is no alcohol present in the breath sample, no oxidation will occur. Because no electrons will be released, no
current will be generated and the result displayed will be a zero reading.

Fuel Cell Diagram

Fuel Cell
Platinum Black
Fuel Cell Housing
Porous Substrate
The Alco-Sensor FST fuel cell responds to alcohol in the human breath. It will not respond to acetone which may be found
in the breath of a diabetic, dieter or highly exercised individual. In fact, it has no significant cross sensitivity to any known
substance that might be found in a living human subject after a 15-minute deprivation period.
Breath
ALCOHOL
O
2
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Acetic Acid
H O CO
2 2
Alco-Sensor FST Operator Manual, Page 10 of 33, 11/30/2017
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