Correct answer: 0.15 milligrams of alcohol per liter of exhaled air.

Until you’ve held your first license for two years, you’re a novice driver for alcohol-limit purposes. If you’re an adult, you must not exceed 0.15 mg/l in exhaled air or 0.3 g/l in blood; if you’re a minor, the limit is 0.0. The general limit is 0.25 mg/l, while 0.3 mg/l confuses the blood alcohol figure with the breath alcohol figure.

Reglamento General de Circulación (Real Decreto 1428/2003) · Texto refundido de la Ley sobre Tráfico, Circulación de Vehículos a Motor y Seguridad Vial (Real Decreto Legislativo 6/2015)