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This article guide outlines the legal limits, mine site standards, and factors that may affect breath test accuracy.

1. Limits

1.1 Legal driving limit (NSW, Australia – 2022)

• 0.05 BAC = Maximum legal limit for driving.

• Readings between 0.041 – 0.049 BAC are considered approaching the legal threshold.

1.2. Mine site limits (NSW, Australia – 2017)

• 0.02 BAC = Standard alcohol limit for most mine sites.

• Readings between 0.011 – 0.019 BAC are treated as close to the limit.

1.3. Light standard drinks

• 0.01 BAC = Typically equivalent to 1–2 “light” standard drinks.

2. Factors

Even the most accurate BAC breathalysers can give false readings if alcohol is present in the breath from sources other than drinking, such as certain substances. This can lead to serious legal, work, family, and community issues. Always ensure tests are done in controlled, contamination-free environments.

Substances that may interfere include:

• Cigarettes

• Environmental factors

• Food

• Medication

• Medical conditions

2.1. Cigarettes

Cigarette smoke contains about 1% hydrogen, which can oxidize at a platinum electrode and cause a small false positive. Always allow a 15-minute gap after smoking before BAC testing.

2.2. Environmental factors

Exposure to volatile substances may influence BAC readings. Examples include:

• Cleaning fluids
• Glues and adhesives
• Paints, lacquers, thinners, and removers
• Auto-finishing sprays

✅ If a positive result occurs, enforce a 15-minute waiting period before retesting.

2.3. Food

Vinegar and fruit

Wine vinegars can contain trace amounts of alcohol. Certain fruits (e.g., overripe dates) may reach up to 4.5% alcohol, though this is rare.

Theoretically, fermentation inside the human body is not physiologically possible at a scale that would affect BAC readings. It would require an inconceivable amount of sugar conversion.

The process would also generate huge volumes of carbon dioxide, which would be clinically obvious.

Fermented items

Some foods (e.g., pizza, fermented items) can release gas during reflux or burping.

This may cause a temporary low-level BAC reading, which typically drops back to zero on a repeat test.

Booker J.L., et al, J. Forensic Sci. 60(6), 1516-1522 (2015) confirms that gastro-esophageal reflux is not a significant factor unless alcohol is present in the stomach at very high levels.

Confectionery

Certain sweets and snacks may influence BAC readings:

• Cough drops (especially those with menthol)
• Mints and chewing gums
• Energy drinks & protein bars
• Liqueur-filled chocolates

2.4. Medication

Common sources include cold and flu liquids, allergy tablets, prescription medications, breath fresheners, asthma inhalers, and scented products used near the mouth, such as aftershaves and mouthwashes.

Mouth alcohol combined with breath alcohol can affect test results. Some oral medicines contain alcohol, and even small amounts may influence a BAC test.

Australian Police require a 15-minute wait after a failed active test before a confirmatory test. In industry, wait 15 minutes after a failed passive test before an active test. If only active tests are used, wait 15 minutes between the first and second tests to avoid interference from recently ingested substances.

Company policy should require a 15-minute wait if workers report eating, drinking, or smoking in the previous 15 minutes.

2.5. Medical conditions

Diabetic breath can contain acetone levels up to 1000 times higher than normal due to fat breakdown. Fuel cell breathalysers show little response to this, while semiconductor breathalysers react strongly.

Hypoglycaemia may cause symptoms like dizziness, clumsiness, and confusion, which can resemble intoxication.

3. Breathalysers

3.1. Overview

Breathalysers detect alcohol to help determine grounds for arrest or disciplinary action, as outlined in AS 3547 — 1997 for breath alcohol testing devices.

If someone tests above the legal limit, especially in zero-tolerance industries, they may claim not to have consumed alcohol. Such claims are often dismissed as attempts to avoid consequences.

However, there are rare cases where BAC readings are not due to alcohol consumption, warranting closer examination.

Even advanced fuel cell breathalysers can register a reading, but quality devices are designed to be sensitive only to ethanol.

Understanding what can trigger positive breathalyser results is crucial for accurate testing, particularly in industries with strict zero-tolerance policies.

Clear policies and proper procedures for using breathalysers help prevent misuse.

3.2. Testing

Passive testing requires no contact with the device; the subject simply talks or blows across the breathalyser. This method is popular for zero-tolerance sites that test all workers before sign-on.

Any result other than zero means further investigation is needed to determine the exact BAC. Mouthpiece testing, which requires each subject to blow into the device using a disposable mouthpiece, provides more accurate results.

There are two main breathalyser technologies: semiconductor and fuel cell. Fuel cell breathalysers, used by police, are more accurate. Semiconductor devices can give false positives due to substances like ketones, cigarette smoke, diabetic breath, hair sprays, or mouthwashes.

Fuel cell breathalysers, such as those from Alcolizer Technology, are highly accurate and reliable when properly calibrated and used.