Measurement of Breath Alcohol

 

The ratio of ethanol in blood to that in the breath is usually reported as 2100: 1. The actual ratio is variable and may be closer to 2300:1. Using the 2100:1 ratio means that the estimated blood alcohol will be slightly lower than the actual level (the level in 2.3 L would be about 9.5% greater than that in 2.1 L), which favors the subject.

 

grams of ethanol in 210 L =

= grams of ethanol per dL

 

Measurement of breath alcohol:

(1) The measurement is done after waiting 15 minutes. This allows for any alcohol in the mouth to clear.

(2) Measurements are taken in duplicate within 30 minutes of each other.

(3) During the absorptive phase after ethanol ingestion, the alcohol level in arterial blood will be slightly higher than that in peripheral venous blood.

Breath Ethanol Level	DOT Guidelines
< 0.02 g in 210 L	no action
0.02 to < 0.04 g in 210 L	no safety sensitive duties for 8 hours; no motor vehicle operation for 24 hours
>= 0.04 g in 210 L	suspend from duty until evaluation by a substance abuse professional