For the Defense - Volume 1, Issue 3 - 2016 - 46
A Discussion of
Breath Alcohol
Testing
Roger M. Hawk, Ph.D.
Introduction
B
reath samples worldwide are used to quantitatively determine whether an individual is
above the statutory level for intoxication.
Breath alcohol levels do not validate intoxication. Rather, it is the blood alcohol level
interacting with the central nervous system, primarily the brain, which causes intoxication. This
blood alcohol interaction causes physiological and
psychological changes which evidence impairment
by altered physical and mental performance.
All U.S. breath testing machines use a
mathematical relationship (partition ratio) to
approximate the amount of alcohol in the blood
(100 milliLiters) based upon the amount of alcohol detected in a breath sample (210 Liters). The
conversion ratio of 2100:1 assumes that for each
molecule of alcohol detected in a given volume of
breath, there are 2100 molecules of alcohol in the
same volume of blood.
The breath machine sample analysis relies on
the application of two Laws - Henry's Law1 2and
the Beer-Lambert Law.3
Henry's Law Considerations
Henry's Law relates the equilibrium concentration of a dissolved gas in a liquid to its
concentration in the air above the liquid.
The proportionality constant (partition ratio)
46
For The Defense | Vol. 1, Issue 3
between the liquid and air concentrations is a
scientific principle relating to dilute solutions of
ideal gases dissolved in liquids.
A simple analogy of making coffee in the
morning can be used to explain Henry's Law. If
someone has turned on the coffee pot, you do
not have to be in the kitchen to know that the
coffee is brewing - some of the coffee escapes
into the air giving the aroma of the fresh brewed
coffee. Obviously, most of the coffee remains in
the pot, but a small amount enters the air in the
kitchen. Eventually, the coffee aroma makes its
way throughout the house.
Henry's Law requires: 1.) constant pressure
above the liquid in the pot, 2.) constant temperature of the pot liquid, and 3.) the liquid must
be in direct contact with the air in the pot. If
these three constraints are satisfied, then you can
calculate the amount of coffee in the pot and
the amount of coffee that escapes into the room.
The ratio of coffee remaining in the pot to the
amount escaping into the room air is called the
partition ratio.
During the calibration phase with breath testing machines, Henry's Law requirements are met
and valid alcohol values are obtained. For a human
subject sample, a much different situation exists.
First, the breath temperature varies from the
lower lung region until the sample is delivered
into the breath machine. Second, the air pressure
Table of Contents for the Digital Edition of For the Defense - Volume 1, Issue 3 - 2016
Contents
For the Defense - Volume 1, Issue 3 - 2016 - 1
For the Defense - Volume 1, Issue 3 - 2016 - 2
For the Defense - Volume 1, Issue 3 - 2016 - Contents
For the Defense - Volume 1, Issue 3 - 2016 - 4
For the Defense - Volume 1, Issue 3 - 2016 - 5
For the Defense - Volume 1, Issue 3 - 2016 - 6
For the Defense - Volume 1, Issue 3 - 2016 - 7
For the Defense - Volume 1, Issue 3 - 2016 - 8
For the Defense - Volume 1, Issue 3 - 2016 - 9
For the Defense - Volume 1, Issue 3 - 2016 - 10
For the Defense - Volume 1, Issue 3 - 2016 - 11
For the Defense - Volume 1, Issue 3 - 2016 - 12
For the Defense - Volume 1, Issue 3 - 2016 - 13
For the Defense - Volume 1, Issue 3 - 2016 - 14
For the Defense - Volume 1, Issue 3 - 2016 - 15
For the Defense - Volume 1, Issue 3 - 2016 - 16
For the Defense - Volume 1, Issue 3 - 2016 - 17
For the Defense - Volume 1, Issue 3 - 2016 - 18
For the Defense - Volume 1, Issue 3 - 2016 - 19
For the Defense - Volume 1, Issue 3 - 2016 - 20
For the Defense - Volume 1, Issue 3 - 2016 - 21
For the Defense - Volume 1, Issue 3 - 2016 - 22
For the Defense - Volume 1, Issue 3 - 2016 - 23
For the Defense - Volume 1, Issue 3 - 2016 - 24
For the Defense - Volume 1, Issue 3 - 2016 - 25
For the Defense - Volume 1, Issue 3 - 2016 - 26
For the Defense - Volume 1, Issue 3 - 2016 - 27
For the Defense - Volume 1, Issue 3 - 2016 - 28
For the Defense - Volume 1, Issue 3 - 2016 - 29
For the Defense - Volume 1, Issue 3 - 2016 - 30
For the Defense - Volume 1, Issue 3 - 2016 - 31
For the Defense - Volume 1, Issue 3 - 2016 - 32
For the Defense - Volume 1, Issue 3 - 2016 - 33
For the Defense - Volume 1, Issue 3 - 2016 - 34
For the Defense - Volume 1, Issue 3 - 2016 - 35
For the Defense - Volume 1, Issue 3 - 2016 - 36
For the Defense - Volume 1, Issue 3 - 2016 - 37
For the Defense - Volume 1, Issue 3 - 2016 - 38
For the Defense - Volume 1, Issue 3 - 2016 - 39
For the Defense - Volume 1, Issue 3 - 2016 - 40
For the Defense - Volume 1, Issue 3 - 2016 - 41
For the Defense - Volume 1, Issue 3 - 2016 - 42
For the Defense - Volume 1, Issue 3 - 2016 - 43
For the Defense - Volume 1, Issue 3 - 2016 - 44
For the Defense - Volume 1, Issue 3 - 2016 - 45
For the Defense - Volume 1, Issue 3 - 2016 - 46
For the Defense - Volume 1, Issue 3 - 2016 - 47
For the Defense - Volume 1, Issue 3 - 2016 - 48
For the Defense - Volume 1, Issue 3 - 2016 - 49
For the Defense - Volume 1, Issue 3 - 2016 - 50
For the Defense - Volume 1, Issue 3 - 2016 - 51
For the Defense - Volume 1, Issue 3 - 2016 - 52
For the Defense - Volume 1, Issue 3 - 2016 - 53
For the Defense - Volume 1, Issue 3 - 2016 - 54
For the Defense - Volume 1, Issue 3 - 2016 - 55
For the Defense - Volume 1, Issue 3 - 2016 - 56
For the Defense - Volume 1, Issue 3 - 2016 - 57
For the Defense - Volume 1, Issue 3 - 2016 - 58
For the Defense - Volume 1, Issue 3 - 2016 - 59
For the Defense - Volume 1, Issue 3 - 2016 - 60
For the Defense - Volume 1, Issue 3 - 2016 - 61
For the Defense - Volume 1, Issue 3 - 2016 - 62
For the Defense - Volume 1, Issue 3 - 2016 - 63
For the Defense - Volume 1, Issue 3 - 2016 - 64
For the Defense - Volume 1, Issue 3 - 2016 - 65
For the Defense - Volume 1, Issue 3 - 2016 - 66
For the Defense - Volume 1, Issue 3 - 2016 - 67
For the Defense - Volume 1, Issue 3 - 2016 - 68
For the Defense - Volume 1, Issue 3 - 2016 - 69
For the Defense - Volume 1, Issue 3 - 2016 - 70
For the Defense - Volume 1, Issue 3 - 2016 - 71
For the Defense - Volume 1, Issue 3 - 2016 - 72
For the Defense - Volume 1, Issue 3 - 2016 - 73
For the Defense - Volume 1, Issue 3 - 2016 - 74
For the Defense - Volume 1, Issue 3 - 2016 - 75
For the Defense - Volume 1, Issue 3 - 2016 - 76
For the Defense - Volume 1, Issue 3 - 2016 - 77
For the Defense - Volume 1, Issue 3 - 2016 - 78
https://www.nxtbook.com/nxtbooks/PACDL/FORTHEDEFENSE_vol9_issue1_2024
https://www.nxtbook.com/nxtbooks/PACDL/FORTHEDEFENSE_vol8_issue4_2023
https://www.nxtbook.com/nxtbooks/PACDL/FORTHEDEFENSE_vol8_issue3_2023
https://www.nxtbook.com/nxtbooks/PACDL/FORTHEDEFENSE_vol8_issue2_2023
https://www.nxtbook.com/nxtbooks/PACDL/FORTHEDEFENSE_vol8_issue1_2023
https://www.nxtbook.com/nxtbooks/PACDL/FORTHEDEFENSE_vol7_issue4_2022
https://www.nxtbook.com/nxtbooks/PACDL/FORTHEDEFENSE_vol7_issue3_2022
https://www.nxtbook.com/nxtbooks/PACDL/FORTHEDEFENSE_vol7_issue2_2022
https://www.nxtbook.com/nxtbooks/PACDL/FORTHEDEFENSE_vol7_issue1_2022
https://www.nxtbook.com/nxtbooks/PACDL/FORTHEDEFENSE_vol6_issue4_2021
https://www.nxtbook.com/nxtbooks/PACDL/FORTHEDEFENSE_vol6_issue3_2021
https://www.nxtbook.com/nxtbooks/PACDL/FORTHEDEFENSE_vol6_issue2_2021
https://www.nxtbook.com/nxtbooks/PACDL/FORTHEDEFENSE_vol6_issue1_2021
https://www.nxtbook.com/nxtbooks/PACDL/FORTHEDEFENSE_vol5_issue4_2020
https://www.nxtbook.com/nxtbooks/PACDL/FORTHEDEFENSE_vol5_issue3_2020
https://www.nxtbook.com/nxtbooks/PACDL/FORTHEDEFENSE_vol5_issue2_2020
https://www.nxtbook.com/nxtbooks/PACDL/FORTHEDEFENSE_vol5_issue1_2020
https://www.nxtbook.com/nxtbooks/PACDL/FORTHEDEFENSE_vol4_issue4_2019
https://www.nxtbook.com/nxtbooks/PACDL/FORTHEDEFENSE_vol4_issue3_2019
https://www.nxtbook.com/nxtbooks/PACDL/FORTHEDEFENSE_vol4_issue2_2019
https://www.nxtbook.com/nxtbooks/PACDL/FORTHEDEFENSE_vol4_issue1_2019
https://www.nxtbook.com/nxtbooks/PACDL/FORTHEDEFENSE_vol3_issue4_2018
https://www.nxtbook.com/nxtbooks/PACDL/FORTHEDEFENSE_vol3_issue3_2018
https://www.nxtbook.com/nxtbooks/PACDL/FORTHEDEFENSE_vol3_issue2_2018
https://www.nxtbook.com/nxtbooks/PACDL/FORTHEDEFENSE_vol3_issue1_2018
https://www.nxtbook.com/nxtbooks/pacdl/FORTHEDEFENSE_vol2_issue4_2017
https://www.nxtbook.com/nxtbooks/pacdl/FORTHEDEFENSE_vol2_issue3_2017
https://www.nxtbook.com/nxtbooks/pacdl/FORTHEDEFENSE_vol2_issue2_2017
https://www.nxtbook.com/nxtbooks/pacdl/FORTHEDEFENSE_vol2_issue1_2017
https://www.nxtbook.com/nxtbooks/PACDL/FORTHEDEFENSE_vol1_issue4_2016
https://www.nxtbook.com/nxtbooks/PACDL/FORTHEDEFENSE_vol1_issue3_2016
https://www.nxtbook.com/nxtbooks/PACDL/FORTHEDEFENSE_vol1_issue2_2016
https://www.nxtbook.com/nxtbooks/PACDL/FORTHEDEFENSE_vol1_issue1_2016
https://www.nxtbookmedia.com