- Breathalyzers estimate blood alcohol concentration (BAC) by measuring alcohol in exhaled breath
- The legal BAC limit for driving is 0.08% in all 50 U.S. states
- Modern evidential breathalyzers use infrared spectroscopy or fuel cell sensor technology
- Portable breath tests (PBTs) used roadside are less accurate than station-based devices
- Factors like body temperature, breathing patterns, and mouth alcohol can affect readings
- Refusing a breathalyzer test in most states carries automatic license suspension (implied consent laws)
- Breathalyzer results are admissible as evidence in DUI/DWI proceedings
- New Jersey has particularly strict DUI enforcement and implied consent laws
Published: February 2026 | Last Updated: February 2026 | Reading Time: 5 min
How Breathalyzers Work
The Science Behind Breath Alcohol Testing
When you consume alcohol, it is absorbed into the bloodstream through the stomach and small intestine. As blood circulates through the lungs, a portion of the alcohol crosses from the blood into the air in the alveoli (tiny air sacs). When you exhale, this alcohol-containing air can be measured to estimate your blood alcohol concentration.
The ratio of breath alcohol to blood alcohol is approximately 2,100:1 — meaning 2,100 milliliters of alveolar breath contains roughly the same amount of alcohol as 1 milliliter of blood. Breathalyzers use this ratio (called the partition ratio) to convert a breath alcohol measurement into an estimated BAC.
Types of Breathalyzer Technology
Fuel Cell Sensors: Used in most portable breath tests (PBTs). Alcohol in the breath undergoes a chemical reaction on a platinum electrode, generating an electrical current proportional to the alcohol concentration. These are convenient for roadside screening but less precise than laboratory-grade devices.
Infrared Spectroscopy: Used in evidential (station-based) breathalyzers like the Draeger Alcotest and Intoxilyzer. These devices pass infrared light through the breath sample and measure absorption at specific wavelengths characteristic of ethanol. They are more accurate and produce results admissible as primary evidence in court.
Accuracy and Limitations
Factors That Can Affect Results
While modern breathalyzers are generally reliable, several factors can influence accuracy. Mouth alcohol from recent drinking, mouthwash, or breath spray can temporarily inflate readings. Body temperature variations (fever) can affect the breath-to-blood ratio. Breathing patterns — hyperventilating lowers readings while holding your breath raises them. Certain medical conditions like gastroesophageal reflux disease (GERD) can cause stomach alcohol to enter the breath. Environmental factors like paint fumes or chemical exposure may affect some sensor types.
Calibration and Maintenance
To maintain accuracy, breathalyzer devices must be regularly calibrated according to manufacturer specifications, certified by the relevant state agency, operated by trained personnel, and subjected to quality assurance testing. Failure to follow proper calibration and maintenance protocols can be grounds for challenging breathalyzer evidence in court.
Legal Implications
Implied Consent Laws
Every state has implied consent laws, which mean that by obtaining a driver's license, you have implicitly agreed to submit to chemical testing (breath, blood, or urine) if lawfully arrested for suspected impaired driving. Refusing a breathalyzer test in New Jersey results in automatic license suspension, fines, and penalties equivalent to or exceeding a first-offense DUI.
BAC Legal Limits
The per se legal limit for driving in all 50 states is 0.08% BAC. However, you can still be charged with DUI/DWI at lower BAC levels if the officer observes signs of impairment. Commercial drivers face a lower limit of 0.04%, and drivers under 21 face zero-tolerance limits (typically 0.01-0.02%).
Frequently Asked Questions
How long after drinking will a breathalyzer detect alcohol?
Breathalyzers can detect alcohol for approximately 12-24 hours after drinking, depending on the amount consumed. As a general rule, the body metabolizes approximately one standard drink per hour. However, individual factors including weight, metabolism, and food intake affect elimination rates.
Can I beat a breathalyzer test?
No. Common myths about defeating breathalyzers — such as sucking on pennies, using mouthwash, or hyperventilating — are ineffective and, in the case of mouthwash, may actually increase the reading. The only reliable way to pass a breathalyzer test is to not have alcohol in your system.
Are breathalyzer results always accurate?
While modern evidential breathalyzers are highly accurate (within +/- 0.005% BAC when properly maintained), they are not infallible. Instrument malfunction, improper calibration, operator error, and physiological factors can affect results. Defense attorneys may challenge breathalyzer evidence on these grounds.
References
- National Highway Traffic Safety Administration. (2023). Breath Testing for Alcohol.
- Jones, A.W. (2010). The relationship between blood alcohol concentration (BAC) and breath alcohol concentration (BrAC). Forensic Science Review.
- New Jersey Motor Vehicle Commission. (2023). DWI: Driving While Intoxicated.
- Hlastala, M.P. (1998). Physiological errors associated with alcohol breath testing. The Champion.
- Garriott, J.C. (2008). Garriott's Medicolegal Aspects of Alcohol. Lawyers & Judges Publishing.
This article was reviewed by the Valley Spring Recovery Center Editorial Team. For help with alcohol use concerns, call (201) 781-8812 or visit our admissions page.
Valley Spring Recovery Center — Evidence-based addiction treatment in Norwood, New Jersey.