The Intoxilyzer 8000 does not measure the temperature of your breath. It assumes it. The machine is calibrated as if every breath sample arrives at 34 degrees Celsius. Warm breath carries more alcohol vapor, so when your breath runs warmer than the assumption, the reading runs high.
Breath temperature is one of the quieter sources of error in a breath case, and it can move the number more than people expect.
The 34-Degree Assumption
Alcohol moves between liquid and vapor at a rate that depends on temperature. Warmer liquid releases more vapor. Your breath works the same way: the warmer it is, the more alcohol vapor it carries for the same amount of alcohol in your blood. The machine assumes a fixed breath temperature of 34 degrees Celsius and builds that into the result. It does not check whether your breath matched.
The machine treats every breath as if it arrived at 34 degrees Celsius. When your breath is warmer, it carries more alcohol vapor, and the reading climbs by roughly 6 to 8 percent for each degree above the assumption.
Do not miss this
A breath reading at or above 0.08 also starts the 10-day license clock.
A breath result over the limit triggers an administrative suspension on top of the criminal case. You have 10 days from the arrest to demand a formal review hearing with the DHSMV in Clearwater, which protects your license and can secure a 42-day permit. We file that request the same day you hire us. Call or text (727) 761-4318.
Why a Degree Matters
Research on breath temperature has found that the measured alcohol level rises by roughly 6 to 8 percent for each degree Celsius the breath runs above the assumed value. Normal breath temperature varies from person to person and rises with body temperature. A fever, a hot night, exertion, or simply running warm can lift your breath above 34 degrees and push the reading up with it.
How much a warm breath adds
The size of this effect is what makes it matter. The machine’s math assumes your breath leaves your body at about 34 degrees Celsius, and it never measures your breath temperature to check. That assumption is not harmless, because warmer breath carries more alcohol vapor, so a breath that runs even a degree or two above the assumed temperature reads high, on the order of several percent higher for each degree. People run warm for plenty of ordinary reasons, a fever, a cold, recent exertion, or simply their own body running hotter than average, and the machine treats all of them as if they were a flat 34 degrees. This sits right on top of the partition-ratio problem, because temperature is one of the very things that pushes the blood-breath relationship away from the single number the machine assumes. Two assumptions, temperature and ratio, stacked in the same direction, and both of them can run against you.
The Machine Will Not Tell You
The Intoxilyzer 8000 does not record your breath temperature on the result card. There is no line that says how warm your breath was, so there is no way to confirm the 34-degree assumption was correct for you. The error is built in and invisible, which is exactly why it has to be raised.
Why This Matters in Your Case
When your breath ran warmer than the machine assumed, your true level was lower than the number it printed. Paired with the timeline of your night and your condition at the time, breath temperature can be one more reason the reading does not hold up. It often travels with the partition ratio and the margin of error.
What Makes Breath Run Warm
Breath temperature is not fixed. It tracks your core body temperature and the conditions around you. A low-grade fever, a hot and humid Florida night, recent physical exertion, or simply a naturally higher baseline can each carry your breath above the assumed 34 degrees. Core temperature also drifts across the day and, for some people, across hormonal cycles. None of this is unusual, and none of it is something the machine accounts for. It applies one assumption to a person running a fever and to a person who is cold, and prints a number for each as if the assumption were a measurement.
At roughly 6 to 8 percent per degree, breath about a degree and a half warm can lift a true value in the 0.07s across the 0.08 line on the printout.
Why the Machine Assumes Instead of Measures
Measuring breath temperature in real time would take added hardware and calibration the instrument does not carry. Instead of measuring, the Intoxilyzer 8000 adopts a single population average and treats every sample as if it matched. That choice keeps the device simple, but it shifts the risk of error onto the person being tested. Anyone whose breath runs warmer than the average is reported high through no fault of their own, and there is nothing on the card to flag it.
How We Raise It in Your Case
Because the machine never records your breath temperature, we reconstruct it. Booking and medical records can show your body temperature near the time of the test, the weather and the setting speak to the conditions, and your own account fills in exertion and how you felt. Read together with the partition ratio and the margin of error, a warm-breath argument can show the printed number sat above your true level. The point is not that the machine broke. It is that a built-in assumption did not fit you.
The machine assumes a breath temperature it never measured, and that quiet assumption can tilt your number upward. I look at whether anything about you or that night could have run your breath warm, because a fever, an illness, or just your own physiology can add to the reading, and the instrument accounts for none of it. I know the science of how temperature and the partition ratio move a breath result, and I do not let a machine present a warm-breath reading as if it had measured you exactly.
I started out as an Assistant Public Defender in Florida’s Thirteenth Judicial Circuit, in Tampa, and today I am one of six ACS-CHAL Forensic Lawyer-Scientists in Florida, with forensic training in how these instruments work. A breath result is an estimate produced by a machine, and I read its calibration history, its agreement checks, and the assumptions built into the number, so I can show a jury where it does not hold up. Learn more about my background.
Questions About Breath Temperature
Does breath temperature affect a breath test?
Yes. Warmer breath carries more alcohol vapor, so if your breath was warmer than the temperature the machine assumes, the reading can be higher than your true level.
What breath temperature does the Intoxilyzer 8000 assume?
The machine is calibrated as if breath arrives at 34 degrees Celsius. It does not measure your actual breath temperature.
How much can temperature change the result?
Research has found the measured level rises by roughly 6 to 8 percent for each degree Celsius the breath runs above the assumed temperature.
Can I raise breath temperature in my defense?
Yes. When your breath likely ran warmer than 34 degrees, that can be presented as a reason the reading overstated your true blood-alcohol level.
Can body temperature affect a breath test?
Yes. The machine assumes your breath leaves your body at about 34 degrees Celsius and never measures it. Warmer breath carries more alcohol vapor, so a breath that runs above that assumed temperature reads high, by several percent for each degree. Fever, illness, exertion, or individual variation can all raise breath temperature.
Related: the main breath test defense page, how we challenge a breath test, and the margin of error.
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.
