What to Look for in Your Colorado DUI Breath Test

Weld County Courthouse in Greeley, Colorado, where DUI and criminal cases are prosecuted

Weld County Courthouse in Greeley, where Colorado DUI cases are heard.

Understanding the CDPHE Rules That Govern Breath Testing

Most Colorado DUI cases rise or fall on the evidential breath alcohol test (EBAT). These tests are not informal roadside tools — they are governed by strict rules issued by the Colorado Department of Public Health & Environment (CDPHE) in 5 CCR 1005-2.

When those rules are not followed precisely, the breath result may be unreliable, inadmissible, or vulnerable to suppression.

Below are several critical requirements every Colorado DUI breath test must satisfy.

1. The Breath Machine Must Be Properly Certified

Every evidential breath testing instrument must be:

Initially certified by CDPHE, and
Recertified annually thereafter.

A certificate must exist showing the serial number of the machine and the inclusive dates of certification.

If the machine was outside its certification window, the test result is immediately suspect.

2. Calibration Checks Must “Bracket” the Breath Samples

Each EBAT sequence must include assayed reference standards with a known ethanol value of 0.100 g/210L, and that value must fall within 0.090 – 0.110.

Additionally, the two calibration checks must agree within ±10%. If they do not, the machine must terminate the test and print a “No Calibration Correlation” exception.

This is one of the most overlooked failure points in DUI cases.

3. The Two Breath Samples Must Be Within .02

Colorado requires two subject breath samples, and those two samples must agree within 0.020 grams of alcohol per 210 liters of breath.

If they do not:

The machine must terminate the sequence with a “No .02 Agreement” exception, and
The operator must restart the process with a new 20-minute deprivation period.

No .02 agreement means no valid test.

4. The Mouthpiece Must Be Changed Between Breath Samples

CDPHE rules require the operator to use a new, clean mouthpiece for each breath sample.

That means:

One mouthpiece for the first blow,
A different mouthpiece for the second blow.

Re-using the same mouthpiece creates a real risk of contamination from residual alcohol, saliva, or condensation — all of which can artificially inflate the second reading.

Breath-test video often reveals whether this rule was followed. Failure to change the mouthpiece can undermine the integrity of the entire EBAT sequence.

5. The 20-Minute Deprivation Period Is Mandatory

The operator must observe the subject for a full 20-minute deprivation period to ensure the person does not:

Burp, belch, or regurgitate,
Introduce foreign material into the mouth, or
Otherwise contaminate the breath sample.

If any of those occur, the test must be stopped and the entire 20-minute deprivation period repeated.

The subject must also be removed from proximity to the machine between samples to prevent tampering.

6. “Invalid Sample” Means Start Over

If the subject does not provide a valid breath sample meeting minimum measurement requirements, the machine issues an “Invalid Sample” exception — and the operator must again restart the 20-minute deprivation period before retesting.

This is not optional.

7. The Operator Must Properly Document Everything

After testing:

The operator must sign an attestation that the test was performed in compliance with CDPHE rules.
All printouts — including exception messages — must be included in the DUI packet.
EBAT records must be retained for at least five years.

Missing paperwork is not a clerical error — it is a foundational evidentiary defect.

Common Breath-Test Error Codes & What Must Happen

Colorado breath machines print exception messages when something goes wrong. Each message triggers mandatory steps. Ignoring them often destroys the reliability of the test.

❗ INVALID SAMPLE

The subject failed to provide a valid breath sample.

Testing stops.
All printouts are retained.
Retesting requires a new 20-minute deprivation period.

❗ NO 0.020 AGREEMENT

The two samples did not agree within .02.

Testing stops.
All printouts are retained.
Retesting requires a new 20-minute deprivation period.

❗ RANGE EXCEEDED

The result exceeds the instrument’s measurable range.

Testing stops.
The subject may require immediate medical attention.
Retesting requires a new deprivation period.

❗ DEFICIENT SAMPLE

The breath volume was insufficient.

Testing stops.
Operator comments are required.
Retesting requires a new deprivation period.

❗ CALIBRATION CHECK CORRELATION FAILURE

The calibration checks did not match within tolerance.

Testing stops.
Printouts are retained.
The simulator attachment must be inspected before any retest.

❗ INTERFERENT DETECTED

The machine detected a substance other than ethanol.

Testing stops immediately.
Printouts are retained.
The subject must be referred for medical evaluation.
No further breath testing is permitted.

Why These Rules Matter

Breath tests often appear clean — a number prints and the prosecution moves on.

But the reliability of that number depends entirely on whether CDPHE rules were followed to the letter. One missed step can invalidate the entire test.

This is why every DUI breath packet must be dissected line-by-line — not just the result at the top of the page.

Next week: a breakdown of Colorado DUI blood testing rules, where chain-of-custody and lab procedures create another layer of legal exposure.