There is no legal limit on how many times a police officer can give you a breathalyzer during a DUI stop. At the roadside, an officer can retry the handheld preliminary breath test as many times as it takes to get a usable reading, and at the station the standard evidentiary protocol calls for two separate samples, with more if the readings don’t agree or the machine rejects a sample. The number itself isn’t what matters. What matters is that repeated weak or incomplete attempts can be written up as a refusal, with the same consequences as if you had said no outright.
Two Different Devices, Two Different Sets of Rules
Police use two kinds of breath testing equipment, and the number of attempts and the consequences of failing to deliver a sample depend on which one you’re facing.
The first is the Preliminary Breath Test, or PBT. It’s the small handheld unit an officer carries at the roadside, used to help decide whether there’s enough evidence to arrest you. In most states, taking the PBT is voluntary, and declining carries no license penalty or at most a minor civil infraction. Its results are generally too unreliable to serve as the main evidence against you in court.
The second is the evidentiary breath test at the police station or processing facility. This machine is larger, precisely calibrated, and subject to federal and state accuracy standards. These are the readings prosecutors actually use in court, and this is the test implied consent laws require you to submit to after a lawful DUI arrest.
Roadside PBT: No Cap on Attempts
An officer can ask you to blow into the PBT as many times as needed to get a reading the device will accept. Most stops involve one or two attempts, but several things push the number up.
If the device shows an error code, the officer resets it and tries again. If you don’t blow hard or long enough to deliver deep-lung air, the device won’t register, and you’ll be asked to try once more. The most common reason officers restart a PBT is suspected mouth alcohol contamination. Recent mouthwash, a burp, or a sip of something moments before the stop can leave residual alcohol in your mouth that produces a reading far higher than your actual blood alcohol level. Officers are trained to watch for this and will typically wait a few minutes and test again.
Evidentiary Testing at the Station: Two Samples Is Standard
At the station, the protocol in most jurisdictions calls for two separate breath samples taken a few minutes apart. The duplicate sample is a built-in accuracy check. When the two readings sit close to each other, that consistency makes the results more credible in court. When both readings agree, the lower of the two is typically what gets reported as your official BAC.
Before either sample is collected, you’ll sit through a mandatory observation period, usually 15 to 20 minutes depending on the jurisdiction. The officer watches to make sure you don’t eat, drink, smoke, belch, or vomit, because any of those things can introduce mouth alcohol and corrupt the reading. If the officer sees you do any of them, the clock restarts.
Many state regulations require the two readings to fall within a specific agreement tolerance of each other, commonly 0.02 g/210L. When results fall outside that window, it suggests something went wrong with the machine or the sample. The officer may then start a fresh observation period and run another pair of tests, or switch to a blood draw.
Why You Might Be Asked to Blow Again
Mouth Alcohol
Mouth alcohol is the single biggest source of false readings on breath tests, and it’s the reason the observation period exists. The problem isn’t just a recent sip. Gastroesophageal reflux disease (GERD) can quietly push alcohol vapors from your stomach back into your mouth, and you may not feel it happening. When that stomach alcohol mixes with the deep-lung air you’re blowing in, the device reads both sources together and produces an inflated number.1NCBI. The Limitations of Mouth Alcohol Detection Systems in Breath Alcohol Testing: Case Reports
Other common culprits include dental appliances that trap alcohol, acid reflux medications like Ozempic that worsen stomach disturbances, and certain asthma inhalers. If the officer or the machine’s software picks up a pattern consistent with mouth alcohol, the test is thrown out and repeated after another observation period.1NCBI. The Limitations of Mouth Alcohol Detection Systems in Breath Alcohol Testing: Case Reports
Not Enough Air
Evidentiary machines need a minimum volume of air, typically around 1.1 to 1.5 liters in a single continuous breath, to measure deep-lung alcohol accurately. Some people struggle to hit that threshold. Smokers, people with COPD or asthma, elderly individuals, and anyone with reduced lung capacity may need several attempts. The machine rejects the sample and prompts the officer to try again.
When Repeated Attempts Become a Refusal
This is where the real risk lives. You don’t have to say “I refuse” for the officer to treat the encounter as a refusal. Blowing too weakly, blowing for too short a time, putting your lips around the mouthpiece without actually exhaling, or stalling long enough that the officer gives up can all be documented as a refusal. The penalties are the same as if you had flatly declined.
The line between can’t and won’t is a judgment call made by the officer in the moment, and it often ends up fought over in court. If you have a genuine medical condition that affects your lung capacity, say so clearly and early. Some jurisdictions allow reduced volume thresholds, and many will switch to a blood draw instead. Diagnosed respiratory conditions carry real weight if a refusal charge is later contested. A general claim that you tried your best, without any documented medical reason, rarely holds up.
What a Refusal Costs You
Every state has an implied consent law. By getting a driver’s license and driving on public roads, you’ve already agreed in advance to submit to chemical testing if an officer lawfully arrests you for DUI. That agreement covers the evidentiary test at the station, not the voluntary roadside PBT.
The U.S. Supreme Court confirmed in 2016 that breath tests are minimally invasive and can be required as a routine part of a DUI arrest without a warrant. States can impose criminal penalties for refusing a breath test. Blood tests, which involve piercing the skin, require either your consent or a warrant.2Justia Law. Birchfield v. North Dakota, 579 U.S. (2016)
Refusing the post-arrest evidentiary breath test triggers automatic administrative penalties in virtually every state. The most immediate is a driver’s license suspension, typically ranging from six months to a year or more for a first offense. This suspension is a civil penalty imposed by the motor vehicle agency, separate from your criminal DUI case. You can lose your license for refusal even if the DUI charge is later dismissed.
Prosecutors in most states can also tell the jury you refused. Jurors tend to draw the obvious inference, and that inference alone can tip a close case toward conviction.2Justia Law. Birchfield v. North Dakota, 579 U.S. (2016)
Commercial Drivers Face More
If you hold a commercial driver’s license, the stakes rise sharply. Under federal regulations, refusing any chemical test is treated the same as testing positive, and you’re immediately removed from all safety-sensitive duties.3FMCSA. What if I Fail or Refuse a Test A refusal counts as a major offense under federal motor carrier safety rules, carrying a minimum one-year disqualification from operating a commercial vehicle.4FMCSA. Disqualification of Drivers (383.51) That’s on top of whatever your state does to your regular driving privileges. Before you can drive commercially again, you must complete a return-to-duty process with a DOT-qualified substance abuse professional.
Your Right to an Independent Test
After you complete the officer’s breath test at the station, many states give you the right to request your own independent chemical test at your own expense, usually a blood draw at a hospital or clinic you choose. If the state gets to test you, you should be able to test yourself.
You generally have to ask. Officers aren’t always required to tell you the option exists. If you request an independent test, the officer typically must give you a reasonable opportunity to arrange one, though law enforcement isn’t obligated to drive you there. Time matters. Blood alcohol levels change quickly, so the sooner the independent test happens, the more useful it is as a comparison. If the independent result comes back significantly lower, it becomes powerful evidence that the station breathalyzer was off.