An ignition interlock device (IID), such as an Intoxalock unit, is a vehicle breathalyzer installed to prevent driving while under the influence of alcohol. While highly effective at their intended purpose, these devices are built with a specific limitation: they only detect alcohol. Understanding this distinction is crucial for anyone mandated to use an IID or those seeking to understand the technology's capabilities.
The Core Technology: How Intoxalock Works
Intoxalock devices rely on an electrochemical sensor called a fuel cell, which is highly sensitive and specific to ethyl alcohol (ethanol). When a driver blows into the device, the following process occurs:
- A breath sample is drawn into the device's sensor.
- The fuel cell oxidizes any alcohol molecules present in the sample.
- This oxidation process generates an electric current. The stronger the current, the higher the Breath Alcohol Content (BrAC).
- If the measured BrAC is below the set legal limit, the device allows the vehicle to start. If it's above the limit, the ignition is locked. This specialized technology is the reason IIDs are so accurate at measuring alcohol, but it also explains why they cannot detect other substances.
Why Intoxalock Does Not Detect Drugs
Unlike alcohol, most drugs do not possess the same properties that allow them to be easily measured on a person's breath. The reasons for this are rooted in fundamental differences in chemistry and physiology:
- Vapor Pressure: Alcohol has a relatively high vapor pressure, which means its molecules readily convert into a gas that can be exhaled on the breath. In contrast, the active components of most drugs, such as THC in marijuana, have very low vapor pressures, making them difficult or impossible to detect using a simple breath analysis.
- Target Specificity: The fuel cell sensor is specifically designed to react with alcohol molecules, and it does not recognize or respond to the molecular structure of drugs like marijuana, cocaine, or opioids.
What Happens if You Use Drugs While on an IID Program?
Having an Intoxalock device does not provide a loophole for drug-impaired driving. While the IID will not detect drug use, authorities have other means of testing and enforcing impaired driving laws. Key points to remember include:
- Driving Under the Influence (DUI): Operating a vehicle while impaired by drugs is illegal in every state. If a law enforcement officer suspects drug-impaired driving, they can conduct a different set of tests, such as blood, urine, or field sobriety tests.
- Probation and Court Orders: A judge or probation officer can require separate, regular drug testing (like urinalysis) as a condition of probation, in addition to the IID requirement. This is common for individuals with a history of drug-related offenses, even if they also received a DUI for alcohol.
- Device Damage and Violations: Blowing smoke from marijuana or tobacco into the IID can be recorded as a violation and may even damage the sensitive fuel cell sensor. Tampering with the device or attempting to introduce other substances will be flagged as a violation and reported to monitoring authorities.
IID vs. Drug Testing vs. Sobriety Check
| Feature | Ignition Interlock Device (IID) | Standard Drug Testing (Urine/Blood) | Field Sobriety Test (FST) |
|---|---|---|---|
| Purpose | Prevents vehicle from starting if alcohol is present; monitors for alcohol use while driving. | Identifies drug use and presence in the body over a longer timeframe. | Assesses real-time physical impairment and coordination loss. |
| Substances Detected | Alcohol (Ethanol) ONLY. | Various controlled substances (e.g., THC, cocaine, opioids). | Signs of impairment from any substance (alcohol or drugs). |
| Detection Method | Electrochemical fuel cell measures Breath Alcohol Content (BrAC). | Lab analysis of biological samples (urine, blood). | A series of physical tasks, like the Walk-and-Turn or One-Leg Stand. |
| Consequences | Vehicle lockout, violation reported to authorities, extended program time. | Violation of probation, additional legal penalties. | Potential arrest for DUI, leading to legal consequences. |
The Verdict: Understanding Your Responsibilities
In conclusion, while an Intoxalock device is an effective tool for preventing alcohol-impaired driving, it is not a drug detector. For individuals required to have an IID, this means two important things. First, the device provides no protection against legal consequences for drug-impaired driving. Second, the IID is only one part of a potential monitoring program. Judges and probation officers often use IIDs in conjunction with separate, more comprehensive drug testing protocols to ensure full compliance. Responsible drivers must be aware of all their legal obligations and avoid operating a vehicle while impaired by any substance, regardless of whether a breathalyzer will detect it.
For more information on the dangers of drug-impaired driving, consult resources from the National Institute on Drug Abuse (NIDA) or the National Highway Traffic Safety Administration (NHTSA).
Conclusion Intoxalock ignition interlock devices are specifically designed to detect and measure alcohol levels on a person's breath using fuel cell technology. They do not have the capability to detect drugs like marijuana, cocaine, or prescription medications. While the device cannot monitor for drug use, driving under the influence of drugs is still illegal and can be enforced through separate testing methods, such as blood or urine analysis, often mandated by a court or probation officer. Users of IIDs are still subject to all laws regarding impaired driving and should not assume that the device grants immunity from penalties related to drug use.
