Calculation help... Did I just get lucky?!

Convicted Driver Insurance

SillySausage123

Well Known Member
I just wondered what should my readings approximately be for the following

- 3.5 cans (500ml) @ 5%
- 1 pint of fosters @ 4.2/4.5%?

Started drinking at around 9-10pm finished drinking at around 1am

Stats:
Male, height: 165cm weight 75kg

My actual reading was 50 and then 49 breath, which was given at around 3-3:30am. But on my release at around 9-9:30am, I blew 19 which I still feel is incredibly high given my original reading 6 hours prior...
 
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Was your reading at 9am on the big police station machine or a small hand held one?
 
Was your reading at 9am on the big police station machine or a small hand held one?

It was a big one Intoximeter EC/IR if I remember correctly - they had two in the 'Breathalyzer room'. The first breathalyzer machine I used took a while to collaborate, but we eventually took the test, I failed to provide a reading 2-3 times consecutively before I recorded the 50 and 49 readings (due to a mixture of nervousness and technique - felt like a real fitness test). but nevertheless we got there in the end.

During the bail breathalyzer - the original machine was turned off/wasn't working in the morning (he attempted to operate it, but simply moved to the 2nd one) so we used the other one that was there.

The whole procedure was abit of a calamity - The breathalyzer procedure was supposed to be recorded but they couldn't eject the DVD in the end as it got stuck, but they still made me sign a document that stated 'A copy was sealed in my presence', without any amendments stating it was stuck in the recorder. This was then confirmed by the bailing officer that they still couldn't get the DVD out by the morning. The person administering the breathalyser was definitely a newbie, but he had the experienced arresting officer with him at the time. Bless, he was so relieved when another experienced officer asked whether he wanted him to take over the fingerprinting etc stage.
 
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I've just had a look at calculating it using a tool online. 49 seems bang on for the time.

However that 19 reading at 9am is concerning...

I was going to query it at the time with the bailing officer but I just let it go.
 

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I think maths is not your strong point....
You started from 9, whereas you said you started drinking at 9-10pm, so use 10pm.
You have used 3 drinks at 500 x 5%, but you said you drank 3 1/2.
The website gives the answer at the BLOOD alcohol result, not breath so the 49 result you got was showing under the legal limit of 80 for blood.
Worryingly it makes no allowance that for the first half an hour the liver is NOT eliminating the alcohol, but it takes that long - or more- before it starts to process the alcohol you are drinking.
I tried the same input as you, but I am 30kg heavier, 6 ft tall (182cm) and much older and it doesn’t seem to give much allowance for a bigger body.
It does not ask about food consumption which can have an effect on the reading.
It does not take into account that you may have had a drink earlier where there was still some of that in your body.
Adjusting the maths to take into account the above alcohol consumption and timings (but still a bit iffy as regards to weight etc) it gives your estimated reading at 3am as 45/46 in breath, and 8 at 9am..... not far away from what you say you produced. Eating late on could have slowed down the elimination process and therefore raised the readings a bit.
 
Thanks Price,

I suppose you're right, I didn't even review the assumptions of the calculations.

In regards to to timings - I was unsure whether I started at 9pm or 10pm but I agree, 10pm should be used.
In terms of quantity consumed, I unfortunately was unable to choose 0.5 intervals, although I probably should have rounded up.

Other external factors: I didn't eat late on but I did eat at around 7pm (rice, which is a fast absorbing carb) prior to drinking.
Other factors which I felt would have influenced my reading would be that I urinated multiple times (7x) during the course of the evening, and also drank 2 pints of water.

I'm still baffled as to how I obtained a reading as high as 19 by 9...

A quote from a sargent:

Police Sargent said:
You're usually kept in until sufficiently sober to be charged and to understand the charge. Also to ensure that you don't go on to drive and commit the same offence again when released. Typically we allow a depletion rate of 10ug/hour, so if you blow 90ug and need to get to 30ug to be legal that will delay you by around 6 hours.

I'd therefore have expected from a reading of 49mg after 5 hours, closer to 0 than closer to the legal limit of 35...
 
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Another Police Sargent (me until a few years ago) used to say that the reduction in a persons breath reading would be in the order of 7 to 11 per hour, depending on the individual.
50 at 3.30 am could reduce by 38 by 9am, so be 12.......19 is not far away and the lower a breath reading goes, the less reliable it is because it is measuring a minute quantity of alcohol in the given volume of breath.
I used 50 in this example - I know the police use the lower reading of 49 - but on the pre-release breath test there would only have been one sample provided.
 
Thanks Price, I just have to accept that it is what it is. Definitely still in the denial stage of the cycle.

Out of interest, had I only kept to the 3.5 drinks that night and breathalysed at around 3am. Would I still have been over the limit - or within the 'excess allowance' threshold
 
Without the pint of Fosters you would have been just under the limit.
Shows you bad for you Fosters is!
 
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