Ignition Interlock Devices: Alcohol Detection Timing After Drinking

No Universal "Safe" Time

It is impossible to predict exactly when an interlock device will no longer detect alcohol after a specific amount (e.g., half pint). Detection depends on:

• Individual factors: Weight, sex, age, body water %, metabolic rate, liver enzyme activity, food intake, hydration.
• Drink factors: Alcohol content (ABV), volume, speed of consumption.
• Device factors: Calibration, sensitivity threshold (typically 0.02–0.025% BrAC), temperature compensation.

General Pharmacokinetics

• Peak BrAC occurs ~30–60 min after last sip (absorption phase).
• Elimination is ~0.015% BAC/hr (≈0.015% BrAC/hr) on average, but highly variable (0.01–0.025%).
• A half pint of beer (~200 mL, 5% ABV) ≈ 10 g ethanol → peak ~0.02–0.03% BAC in a 70 kg male; lower in heavier, higher in lighter individuals.

Practical Guidance

• Wait at least 12–24 hours after any drinking before attempting to start an interlock-equipped vehicle.
• Better: Do not drink at all if you must drive an interlock vehicle.
• Personal breathalyzers (fuel-cell) can estimate BrAC but are not calibrated to the interlock and cannot guarantee a pass.
• Violations (failed starts, rolling retest failures) are logged and reported—consequences include license revocation, extended interlock period, fines, jail.

If You Have an Interlock

Treat it as a zero-tolerance system. Any measurable alcohol can trigger a violation. Plan transportation accordingly.