Ignition Interlock Device (IID) — what it is and when states require one
An Ignition Interlock Device is a small breathalyzer wired into a vehicle's ignition. The driver provides a breath sample; if it reads above a state-set limit, the engine does not start. IIDs are ordered by the court or required administratively by the state DMV as a condition of relicensing after certain DUI / DWI convictions and, in some states, after other alcohol-related suspensions.
What an IID does
An IID does two things: a pre-start breath test that prevents the engine from starting if alcohol is detected, and rolling re-testsat intervals while the vehicle is in operation. Tampering or repeated failures are logged and reported by the device's calibration vendor to the state DMV or the supervising court. The driver pays the lease cost directly to an approved provider.
IIDs are not a substitute for a suspended license — they are a condition attached to a restored or restricted license. If a state orders an IID as part of a hardship / occupational / critical-need license, the driver may legally drive only when the IID is installed in every vehicle they operate.
The two questions that matter
1. Is it required at all?
Some states require an IID for allDUI convictions, regardless of blood-alcohol level or whether it's a first offense ("all-offender IID" laws). Other states require an IID only for second and subsequent offenses or for very high BAC readings. All-offender IID expansion is the area of the law that has changed most aggressively in 2024–2025; always verify the requirement directly with your state DMV.
2. For how long?
IID duration is set by state statute and ranges from a few months (first-offender, low-BAC, no priors) to multiple years (multi-offender, refusal, very-high-BAC, accident with injury). The clock typically starts at the date the IID is installed and reported to the state, not at the date of the conviction.
IID duration ranges (visual)
Two example states from the primary-source-verified set. Bands on the timeline are state-statutory months. Run the decoder on a state page for your specific verdict.
California
Cal. Veh. Code §23575.3 — durations escalate with prior count.
Florida
Fla. Stat. §322.2715 — 6 months for a first offense; 12 for a second.
Who installs an IID
States maintain a published list of approved IID providers. Common national providers include LifeSafer, Smart Start, and Intoxalock, but state approvals vary, and several states publish state-specific provider lists. Always confirm the provider you choose is on your state's published list — using an unapproved provider can void the compliance record. The state DMV portal lists approvals.
Cost components
- Installation fee — one-time, paid to the provider
- Monthly lease + calibration — monthly, paid to the provider, varies by state and provider
- Removal fee — paid when the order expires and the device is removed
- State filing fee — paid to the state DMV to record the installation (some states only)
The reinstatement cost-stack calculator on the decoder rolls these up alongside the state DMV reinstatement fee and any SR-22 differential — see the cost-stack pillar.
Federal layer
IID rules are state-statutory. Federal references at 23 CFR §1275 and 23 USC §164 set compliance incentives but do not preempt state implementation. The IID requirement on your specific case is set by the state where the conviction occurred — verify with the state DMV linked in your state page.
State grid — IID frameworks vary
Click any state for the per-cause matrix, IID timeline, and decoder.