Rank: Forum user 
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Does anyone know why some industries allow for a certain amount of alcohol to be detected in an employees system (as an example up to 0013 micrograms of alcohol in 100 millilitres of breath) when carrying out an alcohol test. I am trying to understand why we just don't say zero tolerance and therefore the levels are zero! Any thoughts?
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Rank: Forum user
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My understanding is the low limit is to accomodate for medication / mouth wash etc that can have an alcohol limit. If you said zero - you would exceed this. Also - traces from the previous night could hamper a zero tollerance limit.
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Rank: Super forum user
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Hi John,
I don't have experience in this field, but I suspect that its possibly because some mouthwashes contain alcohol as an ingredient.
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Rank: Super forum user 
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Mainly, just because teh people setting the limit don't think they'd get away with setting a zero limit - they think too many people would fail (or too many people would think they fail).
I think the mouthwash / medication / natural yeasts on fruit thing is a red herring because the levels that it causes are much lower.
The rail limit is a blood alcohol level of 29mg per 100ml (cf a driving limit of 80mg per 100ml)
The USA (or at least many states) have the same basic blood alcohol level of 80mg per 100ml but a 'zero' limit for drivers under 21. However, teh 'zero' limit is actually 10mg per 100ml - or one third what is acceptable in UK rail industry.
Many jurisdiction do actually claim a zero limit for drivers - eg young drivers in New Zealand. There's no technical reason we couldn't have the same in industry in the UK.
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Rank: Forum user
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Very simply, the body has the potential to produce alcohol naturally in the stomach, based on diet and digestion. Therefore a true zero can never be used. 13 is typically used for rail industry and similar safety critical activities. The only one I am aware of more stringent is in commercial aviation, air crew at 10mg / 100ml BRAC.
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Rank: Super forum user 
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As above
+ trouble with zero is you'd have workers in the morning who still presented some breath alcohol. (we burn about 1 unit an hour - 1 pint = 2 units)
Alcoholics may even present a breath alcohol reading with out drinking for a long period!
Also Diabetes can cause acetone to be present in the breath (Caused by Ketosis in the body) - the functional groups are very close to that of Ethanol and can give false positives.
Several drugs can give false positives (But most of them giving a false positive of 35mgm-3 would result in the person providing the sample being dead :) )
In reality if you are using a breath screener that is calibrated and approved by the home office it will only measure deep lung alcohol anyway.
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Rank: Super forum user
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Three thoughts to add to the debate:
I a study of the effect of an alcohol sanitiser it was found that shortly after use there was a detectable level of alcohol in exhaled breath. This disappeared after a short period. There was no indication of skin uptake so presumably the alcohol was inhaled vapour as the product evaporated from the skin.
There was also a study, although I cannot lay my hands on it at the moment, that showed that people in an atmosphere where alcohol was being consumed could show a detectable level in their breath on leaging the premises.
With a 'zero' policy how are you going to measure zero? Your can measure to the lowest detectable limit, but 'zero'?
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Rank: Super forum user
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8 beers of 4% alcohol will mean an 88Kg/40-year male will still be over the dd limit 10 hours later...
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Rank: Super forum user
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chris.packham wrote:Three thoughts to add to the debate:
There was no indication of skin uptake so presumably the alcohol was inhaled vapour as the product evaporated from the skin.
There was also a study, although... detectable level in their breath on leaving the premises.
With a 'zero' policy how are you going to measure zero? Your can measure to the lowest detectable limit, but 'zero'? Exactly - zero is a dream, hence why the government don't use it. My best guess for handwash would be skin absorption, odd that it isn't. The amount inhaled is going to be very very tiny. This is another reason the drink drive limit is what it is. I have seen defendants claim they drank mouth wash, or took medication, or inhaled the breath of a drunk... now this might result in a detectable level, but there is no way blood alcohol could ever reach 35mgm-3! (note I say blood alcohol - all good machines are designed to only sample deep lung breath with will show a head-space reading from the blood)
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