Breathalyzer machines are treated in courtrooms as if they are infallible. They are not. These devices use infrared spectroscopy or electrochemical fuel cell technology to estimate blood alcohol concentration from a breath sample — and there are at least 14 documented substances, conditions, and circumstances that can produce readings significantly higher than your actual BAC.
If any of these apply to you, they may form the basis of a challenge to the breathalyzer evidence in your case. None of this replaces the advice of a qualified DWI attorney — but knowing what factors exist can help you have a much more informed conversation with one.
1. Hand Sanitizer
This one surprises people — and it should be more widely known. Hand sanitizer contains isopropyl alcohol. Breathalyzer machines are calibrated to detect ethyl alcohol (the kind in beverages), but older fuel cell models and some infrared devices can register isopropyl alcohol as a false positive. A video circulating online shows a police officer applying hand sanitizer immediately before administering a roadside breath test. Defense attorneys have used similar facts in actual cases to challenge results. If an officer handled your test right after using hand sanitizer, that is worth documenting and discussing with your attorney.
2. Mouthwash
Listerine original formula is approximately 26.9% alcohol — higher than most wines. Using mouthwash within 15-20 minutes of a breath test can spike your reading dramatically. Officers are supposed to observe a 15-20 minute deprivation period before administering an evidentiary breath test for exactly this reason. If that observation period was skipped or shortened, the result may be challengeable.
3. Breath Sprays
Many breath freshener sprays contain alcohol as a carrier ingredient. Like mouthwash, using a breath spray shortly before a test can leave residual mouth alcohol that inflates the reading. This is distinct from deep lung air, which is what the machine is supposed to measure.
4. NyQuil and Alcohol-Based Medications
NyQuil contains 10% alcohol. Certain cough syrups, tinctures, and liquid medications can contain similar amounts. Taking a dose before driving and then being stopped can result in elevated breath readings that do not reflect your level of impairment. If you take any liquid medications, always check the label for alcohol content.
5. Paint Fumes, Lacquer, and Varnish
This one hits especially hard for tradespeople. Painters, contractors, woodworkers, and auto body technicians regularly work with solvents that contain compounds chemically similar to alcohol. Infrared breathalyzers in particular can misidentify these compounds as ethyl alcohol. If you were working with solvents before your stop, that is relevant information for your attorney.
6. Acetone from Diabetes
People with diabetes, particularly those with poorly controlled blood sugar, produce elevated levels of acetone in their breath as a byproduct of fat metabolism. Some breathalyzer models cannot distinguish acetone from ethyl alcohol and will register a false positive. Diabetics have successfully challenged DWI charges on this basis. If you are diabetic, mention this immediately to your attorney.
7. Ketogenic Diet and Low-Carb Diets
The keto diet forces the body into a state of ketosis, which produces ketones including isopropanol and acetone. These can register on a breathalyzer as alcohol. A person in deep ketosis who has consumed no alcohol could theoretically blow a non-zero reading. If you were following a strict low-carb or keto diet at the time of your stop, that is worth documenting.
8. GERD and Acid Reflux
Gastroesophageal reflux disease (GERD) causes stomach contents to travel up the esophagus. If you have any alcohol in your stomach and reflux occurs shortly before or during a breath test, stomach alcohol can contaminate the breath sample and produce a reading much higher than your true blood alcohol level. Officers are supposed to watch for signs of belching or reflux during the observation period. If they missed it, that's a potential issue.
9. Burping Right Before the Test
Even without a diagnosed reflux condition, burping immediately before blowing into the breathalyzer can push stomach air containing alcohol into the mouth and lungs. This mouth alcohol contaminates the sample. Again, the observation period is supposed to catch this. If it was skipped or abbreviated, that matters.
10. Chewing Tobacco
Chewing tobacco in the mouth during a breath test can trap alcohol compounds and produce elevated readings. Some research suggests that certain chemicals in smokeless tobacco can interact with fuel cell breathalyzer technology. If you use chewing tobacco, disclose this to your attorney.
11. Asthma Inhalers
Some asthma inhalers contain alcohol as a propellant or carrier. Using an inhaler before a breath test can introduce alcohol compounds into the airway that get picked up by the device. If you use a rescue inhaler and used it shortly before your stop, document the medication and timing.
12. Rising Blood Alcohol
Alcohol is not absorbed instantly. If you had a drink shortly before being stopped, your BAC may have been below .08 while you were actually driving, but it continued to rise after you were pulled over and administered the test. This is called the "rising blood alcohol" defense. It is a legitimate scientific argument that experienced DWI attorneys use regularly in cases where the timing of drinking and testing are close together.
13. Improper Machine Calibration
Breathalyzer machines must be calibrated regularly according to strict protocols. Records of calibration, maintenance, and any malfunctions are public records in most states and must be produced by the prosecution. A machine that was out of calibration on the date of your test is producing unreliable results. Always ask your attorney to request the machine's maintenance records.
14. Residual Mouth Alcohol from Dental Work
Dental procedures sometimes use alcohol-based products. Dental work can also create areas in the mouth where liquid collects. Recent dental procedures followed by a breath test can produce elevated readings from residual oral alcohol rather than blood alcohol. If you had dental work in the days before your arrest, that is worth documenting.
What This Means for Your Case
A breathalyzer reading is not the end of your case. It is a piece of evidence — and like all evidence, it can be challenged, contextualized, and sometimes discredited. The key is identifying which of these factors may apply to you and communicating that information clearly to a qualified DWI attorney as quickly as possible.
If your license was ultimately suspended or revoked as a result of a DWI charge, understanding the reinstatement process is your next step.
License Suspended After a DWI?
Understanding what happened at your stop is important. So is knowing how to get back on the road legally. Our guides walk you through the full reinstatement process.
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