There are actually two types of breath tests in use, the first is performed on the road with an Alco-Sensor and is not admissible in court, the second is performed at the county jail or station and is what is referred to as the breathalyzer. The breathalyzer is formally the EC/IR II machine and it doesn't measure alcohol but rather the byproduct of alcohol in your lungs, ketones. The assumption is that everyone interacting with the machine has the same metabolic rate, which we know is polite fiction, and yet it is admissible in court. Unfortunately, refusing to submit to the test means a warrant for blood can be obtained based on that refusal as well as an administrative suspension of driving privileges for 1 year. So, if you're asked to take the test at all, no matter what you decide, you're going to need an attorney.