Oregon has an implied consent law which establishes when you drive in Oregon, you implicitly consent to a breath, blood, or urine test if asked by an officer. While you may of course refuse to submit to a breath test, there are consequences.
Consequences of refusal
If you ultimately are charged with a DUII, the prosecutor may use your refusal to give a breath test sample against you in court. Likewise, the DMV will suspend your license. The suspension varies based upon your prior history regarding the DUII Implied Consent Law and prior arrests. Additionally, not providing a breath test sample, thus giving the prosecutor your BAC, does not solve your problem of being charged with a DUII.
DUII charges still possible
Remember, the prosecutor can establish the crime of DUII (DUI, DWI) by proving your BAC to a jury or by establishing that, at the time you were driving, you were under the influence of intoxicants. In other terms, the prosecutor proves to a jury that you were impaired to a perceptible degree. An officer can establish such impairment even if they don’t have a breath test, blood test, or urine test to scientifically back up their belief.