2.3 Breath Test Devices
A breath test device is a stationary or portable alcohol sensor used to measure a person’s breath alcohol concentration (BrAC). Law enforcement officers use breath test devices in the field to help establish probable cause for a DWI arrest. A driver blows into a mouthpiece and the breath test device displays a numerical BrAC often converted to BAC terminology such as .12 g/dL.
Several breath test device models are available commercially. There are two categories of breath test devices. Evidential breath test devices are State-approved and conform to established specifications and can be used as evidence in court. Preliminary breath test devices, also known as screeners, are handheld devices used at the roadside by officers to establish probable cause prior to arrest. NHTSA provides a “Conforming Products List” of alcohol testing (EBT) and screening (PBT) instruments, as well as calibration units for these devices. While some States may maintain separate lists of approved devices they have tested and approved for purchase, devices included on NHTSA’s Conforming Products Lists are eligible for purchase using Federal funds.
- NHTSA Conforming Products List of Evidential Breath Alcohol Measurement Devices, Docket No. NHTSA–2017–0053, Federal Register, Vol. 82, No. 211, Thursday, November 2, 2017), available at www.nhtsa.gov/sites/nhtsa.dot.gov/files/documents/2017-23869.pdf
- NHTSA Conforming Products List of Screening Devices to Measure Alcohol in Bodily Fluids, Docket No. NHTSA–2012–0062, Federal Register, Vol. 77, No. 115, Thursday, June 14, 2012, available at www.nhtsa.gov/sites/nhtsa.dot.gov/files/documents/cpl_asds_june_2012.pdf
- NHTSA Conforming Products List of Calibrating Units for Breath Alcohol Testers, Docket No. NHTSA–2012–0063, Federal Register, Vol. 77, No. 204, Monday, October 22, 2012, available at www.nhtsa.gov/sites/nhtsa.dot.gov/files/documents/cpl_cus_oct_2012.pdf
Use: PBTs are often used to establish probable cause for arrest, but they are rarely used as evidence in court. One exception is California, which allows PBT results as evidence of presence of alcohol (Nesci, 2015). California officers can use PBT evidence to enforce zero-tolerance laws for drivers under 21; an officer at the roadside can issue a citation and seize the driver’s license (Ferguson et al., 2000). EBTs are commonly used to provide evidence of alcohol impairment that is presented in court.
Effectiveness: Law enforcement officers generally agree that breath test devices are useful. Sixty-nine percent of the 2,731 LEOs surveyed by Simpson and Robertson (2001) supported greater breath test devices availability and use. Breath test devices are especially valuable for two classes of drivers who may appear to perform normally on many tasks: drivers with high tolerance to alcohol (Simpson & Robertson, 2001) and drivers under 21 who may be in violation of zero-tolerance laws (Ferguson et al., 2000). A breath test device also can be useful at crash scenes where a driver is injured and unable to perform an SFST. There is some evidence that breath test devices use increases DWI arrests and reduces alcohol-involved fatal crashes (Century Council, 2008).
Costs: Breath test devices cost from $200 to $2,000 a piece, with PBTs typically costing less than EBTs. Many LEAs have limited numbers of breath test devices and many patrol officers do not have regular access to them. Officers surveyed by Simpson and Robertson (2001) estimated that three-fourths of all DWI arrests occur on routine patrols, so DWI detection would be substantially improved if every patrol officer had a breath test device.
Time to implement: Breath test devices can be used as soon as they are purchased and officers are trained in their use and maintenance, especially regular calibration checks. Most LEAs have the facilities to conduct these checks.
- The “one test” rule: Some State statutes allow only one chemical BAC test to be taken from a driver arrested for DWI. These States do not use PBTs because an evidential BAC test cannot be requested if an officer previously has taken a PBT test in the field.
- Other drugs: The PBT and EBT devices commonly used are designed strictly for identifying alcohol and cannot detect the presence of drugs other than alcohol.
- Personal breath-testing devices: It is important to note that these devices are not used by law enforcement and they do not meet NHTSA’s Model Standards. Personal breath-testing devices can be paired to smartphones to record breath samples and deliver cautionary messages and notifications of BACs to drivers including safety measures to hail a ride share or alert social contacts. Smartphone cameras can be used to verify driver identity and to provide time-stamped and georeferenced breath sample record. One limitation of these personal breath-testing devices is the requirement of active use and engagement provides only point-in-time BAC estimates. A point-in-time BAC estimate could create a hazardous situation where someone’s BAC is rising, but the device indicates that the person is below the illegal per se limit leading them to drive.
 A BAC measures the weight of alcohol (usually in grams) per volume of blood (usually deciliters, centiliters, or milliliters, commonly expressed in NHTSA reports as grams per deciliter, g/dL). A BrAC measures the weight of alcohol in a volume of breath, usually grams per 210 liters (g/210L). Some breathalyzers report readings as BrACs, g/210L, and some convert the BrAC to BAC terminology, g/dL.