Key Takeaways
- Smoking cigarettes produces acetaldehyde, a compound that breathalyzers can mistake for ethanol alcohol.
- Vaping with e-cigarettes can also introduce interfering substances and mouth alcohol that skew BAC readings.
- Under Colorado law (C.R.S. § 42-4-1301), a BAC of 0.08% or higher triggers a DUI charge — even a small false elevation matters.
- A 15-minute observation period is required before testing, but officers don’t always comply, creating a defense opportunity.
By Mark S. Rubinstein, Criminal Defense Attorney | Last Updated: [27th March, 2026]
If you smoke cigarettes or use e-cigarettes, you may not realize that these habits can affect your breathalyzer test results, potentially leading to a falsely elevated blood alcohol concentration (BAC) reading. As a Colorado DUI defense firm, we have seen cases where a client’s smoking or vaping habit contributed to an inaccurate breathalyzer reading that formed the basis of a DUI charge.
Does smoking affect breathalyzer tests? If you find yourself in a situation involving a breathalyzer test or facing DUI charges, don’t navigate it alone. Seek professional legal advice. Contact us today for a confidential consultation with experienced attorneys who can guide you through the process and explore your defense options.
How Do Breathalyzer Tests Work?
Breathalyzer devices measure the alcohol content in your breath by detecting ethanol molecules in the air you exhale from your lungs. The device uses either infrared spectroscopy or an electrochemical fuel cell to estimate your blood alcohol concentration (BAC).
The problem is that these devices aren’t perfect. They are designed to detect ethanol, but they can also react to other chemical compounds with similar molecular structures. This is known as “mouth alcohol” contamination, residual alcohol or alcohol-like substances in your mouth, throat, or esophagus that haven’t been absorbed into your bloodstream.
Common sources of breathalyzer false positives include medications, certain medical conditions like GERD or diabetes, mouthwash containing alcohol, and, as we’ll discuss in detail, smoking and vaping.
How Cigarette Smoking Causes False Breathalyzer Readings
When you smoke a cigarette, the combustion process produces a chemical compound called acetaldehyde. Acetaldehyde has a molecular structure similar to ethanol (drinking alcohol), and many breathalyzer devices cannot distinguish between the two.
Studies have shown that smoking a cigarette shortly before a breathalyzer test can cause the device to register a BAC reading that is artificially elevated. Research published in forensic science journals found that smokers who had not consumed any alcohol still produced detectable readings on certain breathalyzer models due to acetaldehyde interference.
This effect is most pronounced within 15-20 minutes of smoking. The acetaldehyde lingers in your mouth and airway, and when you blow into the device, it registers alongside — or in place of — actual ethanol. This is why law enforcement protocols require a 15-minute observation period before administering a breath test, during which the subject should not smoke, eat, drink, or belch.
Can Vaping or E-Cigarettes Affect a Breathalyzer Test?
Yes — vaping and e-cigarettes can also affect breathalyzer test results, though the mechanism differs slightly from traditional cigarettes.
E-cigarette liquids (vape juice) typically contain propylene glycol, vegetable glycerin, nicotine, and flavorings. When heated, propylene glycol can break down into compounds that some breathalyzer devices mistake for alcohol. Additionally, certain flavored vape liquids contain trace amounts of actual ethanol as a solvent.
The vapor from e-cigarettes can also create a “mouth alcohol” effect similar to using mouthwash. The residual vapor coats the lining of your mouth and throat, and when you exhale into a breathalyzer within minutes of vaping, the device may detect these interfering substances. While the research on vaping and breathalyzer interference is still emerging, several DUI defense attorneys across the country — including here in Colorado, have successfully raised vaping as a contributing factor to inaccurate BAC readings.
Colorado DUI Law and Breathalyzer Accuracy
Under Colorado Revised Statutes § 42-4-1301, driving with a BAC of 0.08% or higher constitutes Driving Under the Influence (DUI), while a BAC between 0.05% and 0.08% may result in a Driving While Ability Impaired (DWAI) charge. When you consider that the difference between a DWAI and a DUI, or between no charge and a DWAI, can come down to hundredths of a percentage point, the accuracy of your breathalyzer reading matters enormously.
Colorado’s Express Consent Law (C.R.S. § 42-4-1301.1) requires that breath tests follow specific protocols, including:
- A 15-minute continuous observation period before testing (the officer must watch you and confirm you haven’t smoked, eaten, belched, or put anything in your mouth)
- Proper calibration and maintenance records for the testing device
- Administration by a certified operator
If the officer failed to observe the full 15-minute waiting period, particularly if you were smoking or vaping before or during that window, the test results may be subject to challenge in court.
How to Challenge a Breathalyzer Result Affected by Smoking or Vaping
If you are a smoker or vaper who was charged with DUI in Colorado based on a breathalyzer test, several defense strategies may apply to your case:
1. Observation Period Violation — If the officer did not properly observe you for 15 minutes before the test, or if you smoked or vaped during that period, the results may be inadmissible.
2. Acetaldehyde Interference — Expert testimony can demonstrate that acetaldehyde from smoking caused a falsely elevated BAC reading, particularly if your actual blood alcohol level (from a blood test) was significantly lower.
3. Device Limitations — Not all breathalyzer models are equally susceptible to interference. The specific device used and its calibration history can be examined to show it was prone to false positives.
4. Rising BAC Defense — If you smoked recently and your BAC was borderline, the combination of smoking interference and the natural rise of BAC after your last drink may mean your actual BAC while driving was below the legal limit.
An experienced Colorado DUI defense attorney can evaluate the specific circumstances of your case and determine whether smoking or vaping may have contributed to an inaccurate result.
Don’t let a faulty BAC test define you. Call Mark S. Rubinstein, P.C. today.
Other Common Causes of Breathalyzer False Positives
While this article focuses on smoking and vaping, it’s important to know that many other factors can cause inaccurate breathalyzer readings. These include:
- Medications — Certain asthma inhalers (albuterol), cough syrups, and oral medications containing alcohol can trigger false positives. [Read our full guide: What Medications Cause False Breathalyzer Test Readings → internal link to /what-medications-cause-false-breathalyzer-test-readings/]
- Medical conditions — Gastroesophageal reflux disease (GERD), acid reflux, and diabetes (ketoacidosis) can all produce mouth alcohol or acetone that breathalyzers misread as ethanol.
- Diet and hygiene products — Low-carb or keto diets produce acetone in the breath, and alcohol-containing mouthwash can temporarily elevate readings.
If any of these factors applied to your situation at the time of your DUI stop, they may strengthen your defense.
Frequently Asked Questions
Q: Does smoking a cigarette before a breathalyzer test affect the results?
A: Yes. Smoking produces acetaldehyde, a chemical compound that many breathalyzer devices mistake for ethanol alcohol. If you smoke within 15-20 minutes of taking a breathalyzer test, your BAC reading may be falsely elevated.
Q: Can vaping set off a breathalyzer?
A: Vaping can potentially affect breathalyzer results. E-cigarette vapor contains propylene glycol and other compounds that some devices detect as alcohol. The vapor can also create a mouth alcohol effect similar to using mouthwash.
Q: How long should I wait after smoking to take a breathalyzer test?
A: Law enforcement protocols require a minimum 15-minute observation period before administering a breath test. Ideally, you should not have smoked for at least 20-30 minutes before the test to minimize acetaldehyde interference.
Q: Can I refuse a breathalyzer test in Colorado if I’ve been smoking?
A: Under Colorado’s Express Consent Law (C.R.S. § 42-4-1301.1), refusing a breath or blood test after a lawful DUI arrest results in automatic license revocation. However, you can request a blood test as an alternative, which is not affected by smoking. Consult with an attorney about your specific rights.
Q: Will smoking weed affect a breathalyzer?
A: Standard breathalyzers measure alcohol (ethanol), not THC from marijuana. However, smoking marijuana shortly before a breathalyzer may introduce combustion byproducts that could theoretically interfere with some devices. If you are suspected of driving under the influence of marijuana in Colorado, officers typically use blood tests or Drug Recognition Expert evaluations rather than breathalyzers.
You Need an Experienced Defense Attorney by Your Side If You Are Arrested for DUI
If you or a loved one has been arrested for DUI in Colorado, you must speak with a lawyer at Mark S. Rubinstein, P.C., as soon as possible. We have an experienced defense legal practitioner, and we know the common errors that are made in administering breathalyzer tests as well as the myriad of other things that can create inaccurate results. These inaccurate results, if not properly defended against, can cause you to be unfairly penalized by our judicial system. Do not let this happen to you. Allow us to put our years of experience and our in-depth knowledge of defenses against DUI convictions to work for you.
A DUI on your record can negatively impact your life for years to come. It can not only affect your ability to drive, but it can even impact your ability to get that job you have been working towards for years. Do not allow your DUI to have any worse impact on your life than necessary. Contact us today for a free consultation by calling our office or filling out our online contact form. We are here for you!
