I see no error in what ribt4t said.
bjcc
Not quite. The pilot in question says that was the cause.
I don’t know where
bjcc gets that from. As far as I’m aware, the pilot said no such thing; he simply couldn't understand how he could possibly have tested positive.
Scientists thought that was the likely cause.
Analysis of the pilot's blood sample proved that the level of alcohol in his blood did not exceed the prescribed limit. It was minute, and consistent with that of a non-drinker.
The pilot and those advising him were, not surprisingly, concerned to find out how the initial test could have given a positive reading.
One possibility was that the screening device didn’t provide an accurate reading. The devices used for ‘field tests’ are not infallible and are not claimed to be.
Extracts from posts by two policeman on another ‘alcohol’ thread:
What you have to take into account is that a breath testing device used on an aircraft or at the roadside is a screening device only. It gives a fairly accurate indication, that gives the required grounds needed for an arrest. I would say in my career about 30% of the people who provided positive breath tests at the roadside gave negative results at the station.
I have to disagree with bjcc.
Many is the time I have used an ESD (Electronic sampling device) at the roadside and the result to bypass the Pass and Warn lights and shoot straight to Positive, only to find that the subject blows under the limit when tested on the EBM at the station a short while later.
These machines are merely indicators that a person MIGHT be over the prescribed limit and they are not infallible.
However, further investigation revealed that the pilot had been on a very low calorie diet for a long period which provided an alternative explanation.
It is known that low-carbohydrate diets can produce acetone which is produced by the body trying to make up the glucose absent from low-carbohydrate diets. It can fool breath test equipment.
Prof. Wayne Jones, a professor in experimental alcohol research, says that breathalysers can sometimes fail to distinguish acetone from drink. "Then there's a risk you get a false positive reading."
From the International Journal of Obesity
False-positive breath-alcohol test after a ketogenic diet.
“A 59-year-old man undergoing weight loss with very low calorie diets (VLCD) attempted to drive a car, which was fitted with an alcohol ignition interlock device, but the vehicle failed to start. Because the man was a teetotaller, he was surprised and upset by this result.
VLCD treatment leads to ketonemia with high concentrations of acetone, acetoacetate and β-hydroxybutyrate in the blood.
The interlock device determines alcohol (ethanol) in breath by electrochemical oxidation, but acetone does not undergo oxidation with this detector.
However, under certain circumstances acetone is reduced in the body to isopropanol by hepatic alcohol dehydrogenase (ADH).
The ignition interlock device responds to other alcohols (e.g. methanol, n-propanol and isopropanol), which therefore explains the false-positive result.
This 'side effect' of ketogenic diets needs further discussion by authorities when people engaged in safety-sensitive work (e.g. bus drivers and airline pilots) submit to random breath-alcohol tests.”
FL