Breathalyzers have been in use for decades but there is a false assumption regarding their accuracy because as common citizens we trust that if something is used as a tool for law enforcement then it must be reliable. There are several external factors which may affect breathalyzer blood alcohol (BAC) level accuracy.

Lifestyle, Diet, and Medical Conditions

Edible substances containing ingredients that are similar in chemical structure to alcohol can produce artificially high readings. Substances include everyday items such as Listerine, Altoids or spearmint chewing gum.

Lifestyle habits can also lead to breathalyzer errors. Lungs of smokers and tobacco chewers contain 30% more acetaldehyde levels than individuals who don’t smoke. On average, breathalyzer readings are higher for dieters who are following high-protein diets and diabetics whose bodies convert more acetone into isopropyl alcohol.

Gastroesophageal reflux disease (GERD) is a condition may also raise mouth alcohol levels. GERD causes acid reflux which releases stomach liquids into the throat and mouth. If a person took their last drink one hour before being pulled over, but burped 5 minutes before taking the breathalyzer test, mouth alcohol levels will be proportionately higher than blood levels. A simple belch or burp can be a contributing factor to a high BAC, leading to a DWI or DUI charge.

Over-the-Counter Medicines

Many over-the-counter medicines contain a high percentage of alcohol. Medicine cabinet culprits that influence BAC levels include Nyquil, Vicks Formula 44D, Halls lozenges, Anbesol and toothache drops.

Elevated Body Temperatures

Recovering from the flu or just came from a backyard hot tub house party? If core body temperature is higher than 98.6 degrees F,the BAC reading will be artificially higher. Temperature increases cause vapor pressure in the lungs to expel larger volumes of evaporated alcohol. Research shows that each degree above a normal body temperature of 98.6F can raise BAC readings up to 8 percent.

Industrial Chemicals

Something as innocent as painting a back deck or working for a dry cleaner may create chemical interferences in  BAC levels. Additionally, working in the construction or manufacturing industries, solvents used in gasoline, varnishes and glues can result in false BAC levels.

Mechanical and Technical Issues

Breathalyzer calibration can impact readings, as can existence of naturally higher or lower than average partition ratios (breathalyzers measure based on a standard breath-to-alcohol ratio.)