Failure to wait 15 minutes after placing food, drink, or other materials in the mouth before running the test can provide erroneous results due to possible contamination of the saliva by interfering substances.

Alco-Screen™ is designed and calibrated to be interpreted two minutes after saturation of the reactive pad. Waiting longer than two minutes may result in erroneous results or false positive results.

Alco-Screen™ may be used to detect the presence of alcohol in fluids other than saliva. However, when used in this manner, the color chart on the package does not apply. If alcohol is present in the fluid, a color change ranging from a light green-gray to black to brown will occur as the alcohol concentration increases. Little or no color change may occur with pure alcohol due to the absence of water which is required for
the color change reaction. When testing beverages to determine whether they contain an intoxicating amount of alcohol, a result should not be considered positive unless the pad changes to a very dark brown or black.

Alco-Screen™ is highly sensitive to the presence of alcohol. Alcohol vapors in the air are sometimes detected by the Alco-Screen™. Alcohol vapors are often present in many institutions and homes. Alcohol is a component in many household products such as disinfectants, deodorizers, and glass cleaners. If the presence of alcohol vapors is suspected, the test should be performed in an area known to be free of these vapors (such as outside).