Dr Manhattan Edit: At the start of this year the story of the Bubble-O-Bill nose came to light and highlighted the risks of eating – and gargling and spraying and drinking – and driving.

A magistrate, not satisfied with an applicant’s explanation of having consumed an icecream, conducted his own in-court experiment. And the applicant’s claim was verified – the liquor surrounding the chewing gum nose does contain enough alcohol to register!

This case highlights the importance of the re-test, required approximately ten minutesafter a failed test. If the reading is the product of some form of contamination, it will have cleared in the intervening time and the re-test will be .00%.

An all-too common application most of us deal with is alcohol interlock removal application under s 50AAB of the Road Safety Act.

Part of that process requires the applicant to provide a minimum-six-month history for the interlock.

I’m surprised at how frequently applicants’ histories have a few positive results, indicating someone with alcohol on their breath blew into the device. I’m also surprised at how many times applicants claim those readings were from mouthwash.

Maybe I’m unduly cynical, but I was frequently very sceptical of these claims.

But it turns out there might be some legitimate basis for them.

Mouthwashes do contain some alcohol. For example, Listerine contains about 27% alcohol! (If you follow that link, click on the label & directions button to see Listerine’s alcohol content.)

‘Breath Alcohol Values Following Mouthwash Use‘, (1993) 270 Journal of American Medical Association 2955 reported that gargling mouthwash can produce elevated breath-alcohol readings for up to 6 minutes. (You can also download the abstract.)

For example, Listerine garglers returned these average results:

• after 2 minutes — 0.240% (0.240 grams per 100 ml)
• after 6 minutes — 0.068% (0.068 grams per 100 ml)
• after 15 minutes — 0.008% (0.008 grams per 100 mil)

(The results were in mg/dL: a milligram is one-thousandth of a gram, so 240 mg = 0.240 grams; a decilitre is one-tenth of a litre, or 100 ml.)

So, in some cases those excuses might be true!