AlcoSense Excel Instruction Manual - Page 10

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Driving Abroad > Changing the Blood Breath Ratio

If you are using your AlcoSense breathalyser abroad you may need to

change the Blood Breath Ratio (BBR) setting as well as the drink drive

limit. The BBR is the ratio that is used to convert a breath alcohol reading

(displayed in mg/L) into a blood alcohol reading (displayed in ‰BAC).

Different countries use different BBRs. The UK uses 2300:1 which gives the

highest blood value from a breath reading. A more detailed explanation of

the Blood Breath Ratio is shown on the page opposite.

A list of the common BBR's is displayed overleaf. If you do not know the BBR

in the country you are travelling to, use 2300:1 as this will always give the

highest reading, or change the unit of measure to mg/L (breath alcohol) and

use the local mg/L limit.

To check the current setting please go to Main Menu > Info and scroll down

until you see "Ratio" or "BBR".

To change the BBR go to Main Menu > Settings > Advanced >

Blood Breath Ratio.

WARNING:

Do not forget to reset the BBR to 2300:1 when you return to the UK. Using a

lower BBR in the UK will cause your unit to under-read.

How can a Breathalyser Display a Blood Alcohol Reading?

Breathalysers measure the alcohol concentration in a persons breath and can

convert the breath reading into a blood reading using the Blood Breath Ratio.

The Blood Breath Ratio

IMPORTANT: The Blood Breath Ratio (BBR) used in drink driving law differs

slightly from country to country, but is normally 2000:1, 2100:1, 2200:1

or 2300:1. If the wrong BBR is used in the wrong country, a breathalyser

could give a falsely high or low blood alcohol reading. For example, the UK

uses a BBR of 2300:1 which means a breath reading of 0.22mg/L = a blood

reading of 0.50‰BAC. However, France uses a BBR of 2000:1 which means

a breath reading of 0.22mg/L = a blood reading of 0.44‰BAC. This means

that a motorist who drives from the UK to France using the wrong BBR

setting could be over-reading in France, or a French motorist driving to the

UK could under read. This is why it is very important to select the correct

BBR in Main Menu > Settings > Advanced > BBR. If you do not know the

correct BBR for the country, set it to 2300:1 as this is the option which will

give the higher reading.

The Relationship Between Different Units of Measure

AlcoSense Excel converts the value for you if you choose a different unit of

measure and the correct Blood Breath Ration is set (see relevant section

above). If you wish to convert between units manually the following

explains the relationship between different units of measure:

Breath Units

Blood Units

0.35 mg/L = 35 μg/100mL

0.80‰BAC = 0.080%BAC

To convert a breath reading to a blood reading or vice versa you will need

to know the correct Blood Breath Ratio (see relevant section above) for the

country you are in. You can convert a breath reading to a blood reading

using the following formula:

Reading in mg/L x BBR / 1000 = Reading in ‰BAC