Interferents and Acetone

The Intoxilyzer 8000 identifies alcohol by how it absorbs infrared light. That method is powerful, but it is not perfectly specific to alcohol. Other compounds can absorb in a similar range, and some of them show up in ordinary medical conditions.

When the machine reports a number, it is assuming the only thing it detected was ethanol. That assumption is worth testing.

How the Machine Identifies Alcohol

Infrared detection works by shining light through your breath and measuring which wavelengths get absorbed. Ethanol absorbs at certain wavelengths, and the machine reads those bands. The catch is that the strongest band it uses, around 3.4 microns, comes from a chemical bond that many organic compounds share. The machine adds a second filter to help separate ethanol from look-alikes, and it relies on that step working. Because the instrument looks at only a slice of the infrared spectrum, it cannot fingerprint ethanol to the exclusion of every other compound. Florida’s own appellate courts have acknowledged that the device is known to produce false positives. See State v. Bastos, 985 So. 2d 37 (Fla. 3d DCA 2008).

Near 3.4 microns, ethanol and a look-alike like acetone both absorb, so the first filter alone cannot tell them apart. The machine leans on a second band near 9.3 microns and its software to separate them. Whether that worked for you is a question the data has to answer.

Acetone and Ketosis

The most discussed interferent is acetone. Your body makes more of it when you are in ketosis, which happens with uncontrolled diabetes, fasting, and low-carbohydrate diets. Acetone is volatile and leaves the body partly through your breath. The instrument is supposed to detect an interferent, subtract it, and report a correct number, and it has to do that on every run. When the agency tests for acetone, it adds acetone to a known solution and runs it, and if a control is run several times while the interferent is caught only once or twice, the machine is not behaving the way it should. The printout also carries an INTERFERENT DETECT code that aborts the test when the two filters disagree. Whether all of this worked for a given person, on a given night, is a question the records have to answer, and not an assumption.

Why the machine cannot fully fingerprint alcohol

The reason an interfering compound can slip past is structural, not a fluke. As a Florida court recognized in State v. Bastos, 985 So. 2d 37 (Fla. 3d DCA 2008), the Intoxilyzer reads only a portion of the infrared spectrum, so it cannot fingerprint ethanol to the exclusion of every other compound, and the court acknowledged the instrument is known to produce false positives. That is why the machine has an interferent detector at all. When it flags an interferent it aborts, which is the safeguard working. The real question is what it missed, and whether the person tested was someone whose own body chemistry, diabetes, a low-carbohydrate or ketogenic diet, or fasting, could put an interfering compound on their breath before the machine ever caught it.

Other Sources

Acetone is not the only possibility. Certain industrial and household chemical exposures put volatile compounds in your breath, and some can absorb in the same region the machine reads. The point is not that every reading is wrong. The point is that the machine’s claim to have measured only ethanol has to be earned by the data.

Why This Matters in Your Case

If you have diabetes, were fasting or on a keto diet, or had a chemical exposure, that belongs in front of the court. We check the instrument’s records for any interferent flags and line them up against your medical history and the night’s events. A reading that may not be pure ethanol is a reading a jury can doubt. This pairs closely with how the Intoxilyzer 8000 works and the margin of error.

Why Infrared Can Be Fooled

The Intoxilyzer 8000 identifies alcohol by shining infrared light through the breath and measuring how much is absorbed at certain wavelengths. The catch is that alcohol is not the only compound that absorbs infrared in that region. Other molecules with similar chemical bonds absorb at overlapping wavelengths, and the machine can read that absorption as if it were alcohol. The instrument uses more than one wavelength to improve its odds, but it is not specific to ethanol the way a laboratory method can be.

Compounds that absorb infrared near the same wavelengths as alcohol can lift a reading. The machine measures absorption, and absorption is not unique to ethanol.

Acetone and Other Sources

One well-documented example is acetone, which the body produces and which runs higher in people who are diabetic, fasting, or on a low-carbohydrate diet. Workplace exposure to certain solvents and fumes can also put interfering compounds into the breath. These are not exotic situations. A person can carry an elevated level of an interfering compound for ordinary medical or dietary reasons and have no idea it could touch a breath reading.

What We Look For

We look at your health, diet, medications, and any chemical exposures, alongside the instrument data, to see whether an interfering compound could have contributed to your result. Because the machine cannot tell us on its own that the absorption it measured was pure alcohol, the surrounding facts matter. This often travels with mouth alcohol and the margin of error, each of which can move a reading away from your true level.

A breath machine is often described as if it measures alcohol and nothing else, and a Florida court has already acknowledged that it reads only part of the spectrum and can produce false positives. I look at whether your own chemistry, diabetes, a low-carb diet, or fasting, could have put an interfering compound on your breath, and I look at how the machine handled it. I know the science of how infrared identification works and where it fails, and I do not let a device that cannot fully fingerprint alcohol stand in as if it were flawless.

Questions About Interferents

Can other substances affect a breath test?

Yes. The machine identifies alcohol by infrared absorption, which is not perfectly specific. Other compounds, including acetone from certain medical conditions, can absorb in a similar range.

Can diabetes affect a breath test?

It can. Uncontrolled diabetes can put a person into ketosis, which raises acetone in the breath. Instruments are designed to account for it, but whether that worked should be examined, not assumed.

Can a keto diet or fasting affect a breath test?

Both can raise acetone levels through ketosis. That is one of the conditions worth raising when a breath reading is challenged.

How do you challenge an interferent issue?

We review the instrument’s records for interferent flags, and we line up your medical history and the circumstances against the result to test whether the machine measured only alcohol.

Can diabetes or a low-carb diet affect a breath test?

They can. Diabetes, low-carbohydrate or ketogenic diets, and fasting can put the body into ketosis, which produces acetone, a compound an infrared breath machine can struggle to separate cleanly from alcohol. A Florida court in State v. Bastos recognized that the Intoxilyzer reads only part of the infrared spectrum and is known to produce false positives.

Related: the main breath test defense page, how we challenge a breath test, and how the Intoxilyzer 8000 works.

This page is general information, not legal advice, and it does not create an attorney-client relationship. Breath testing in Florida is governed by Fla. Stat. 316.1932 and 316.1934 and the Florida Administrative Code chapter 11D-8. Procedures and rules change, and every case turns on its own facts. Past results do not guarantee a similar outcome.