Abstract: An alcohol breath testing device comprising a conduit through which human breath air is passed. The conduit contains a chemical material which changes appearance upon being contacted by alcohol vapor. An air float chamber is operably connected to said conduit and has an air valve. The air chamber, air valve, and conduit are designed so that in a predetermined period of time a predetermined amount of breath air is permitted to pass through said device. The linear extent of color change in the chemical material in said predetermined period of time correlates to the concentration of alcohol in said breath air.