External alcohol or other substances such as solvents, cleaning fluids, police car exhaust fumes, or other agents may interfere with the test results.  There are thousands of sources of alcohol that may potentially contaminate the air in the room.  Modern machines try to eliminate this defense by testing the room air in what is referred to as the "ambient air" or "air-blank" tests.  The machine must read a 0.000 to show that the air is clean prior to the test and that the sample chamber is purged of alcohol vapors. If the amount of ambient alcohol exceeds a "significantly detectable level" on the BAC DataMaster it will produce a "Blank Error" status message. Usually this is done by comparing the current blank test with the last blank test and measuring any difference.  According to the manufacturer of the BAC DataMaster, "[t]he blank test should be able to return within .003 of the last blank reading."

Did your officer apply lotion and/or alcohol based hand santizer prior to the test?  Did the cleaning lady at the police station clean with an alcohol based cleaner?  This may be a basis for suppression.