Alcohol testing is performed on donors who are suspected of being under the influence of alcohol, or consuming alcohol recently. Testing is performed using a breath alcohol testing device, commonly referred to as a breathalyzer, or with a urine, hair, or fingernail sample.
Breath alcohol testing can determine if the donor is currently under the influence of alcohol by measuring the donor's blood alcohol content, or BAC, through a breath sample.
Urine alcohol testing measures alcohol use in a different way. Instead of measuring the donor's BAC, the sample is tested for ethyl glucuronide, or EtG. EtG can be present in a urine sample for approximately 48 hours after alcohol consumption stops. In cases where alcohol consumption is heavy, EtG has been detected 72 hours after alcohol consumption ceased.
Similar to urine testing, head hair and fingernail testing for alcohol also works by testing for ethyl glucuronide in the sample. The difference between head hair and fingernail testing is the detection window. Head hair and fingernail samples can provide a usage history much longer than 48 hours, with head hair testing providing usage history of approximately 30 days for every half an inch of hair, and fingernails providing usage history of up to 90 days.