Frequently Asked Questions


Dr. Mike Lynn founded Hound Labs, because he passionately believes the tragedies associated with impaired driving are preventable. As an ER physician at a trauma center and a reserve deputy sheriff, Dr. Lynn has witnessed the consequences of impaired driving too often.

The HOUND® CANNABIS BREATHALYZER is easy to use, like an alcohol breathalyzer. A driver or employee breathes into the mouthpiece on the breathalyzer. The disposable cartridge on the breathalyzer automatically captures a sample large enough to conduct both on-site and confirmatory testing. After the breath has been collected, the cartridge is removed and placed in a small portable processor that then measures THC. Within a few minutes, the results indicate if the donor has used recently. The saved sample can be analyzed at a lab to confirm results.

Yes. The HOUND® BREATHALYZER measures THC in breath to levels <3 trillionths of a gram, or 3 picograms per liter of breath (3 pg/L). This is the sensitivity required to measure recent cannabis use throughout the window of peak impairment identified by researchers.

Yes. Our breathalyzer measures THC in the breath after subjects have consumed a variety of smoked, vaporized, and edible cannabis products.


Breath indicates recent use better than blood, urine, or saliva because THC only remains in breath for a few hours before becoming virtually undetectable; whereas evidence of cannabis use and/or its metabolites can remain in other body fluids for many hours, days, or even weeks after consuming cannabis. The period of time during which THC can be measured in breath aligns with the peak impairment window (2-3 hours) identified by independent researchers [NHTSA].

Because of this narrow window of detection after use, a breathalyzer provides better objective data that an employer can use to determine whether a person used cannabis recently and therefore could still be impaired.


Yes. Although well intentioned, some states have set blood limits for THC to indicate whether a driver is impaired and dangerous behind the wheel. These are called “per se” standards. Unfortunately, THC can remain detectable in blood for days or even weeks, well beyond any peak impairment window (2-3 hours) identified long ago by independent researchers [NHTSA]. This “positive” result means that many people who used cannabis but who are no longer impaired might fail oral fluid, blood, and urine tests.

Other states adopted “zero-tolerance” laws at a time when use of cannabis was illegal. These laws could be enforced regardless of whether or not the presence of THC was causing impairment behind the wheel. Both types of laws – per se and zero tolerance – were established before the HOUND® CANNABIS BREATHALYZER was invented.

With the legalization of cannabis, legislators are beginning to realize that they need new laws to accommodate legal and responsible use while still deterring and monitoring impaired driving and working. A breathalyzer is the best way to balance SAFETY + FAIRNESS™ in the era of legalization because it only measures THC in breath for the few hours that correlate with peak impairment – NOT the presence of THC long after impairment subsides. Understanding whether someone recently used cannabis is a key piece of objective data to help law enforcement and employers determine whether or not the driver or employee may be impaired.

Employers, law enforcement, legislators, unions, and others have communicated an immediate need for the HOUND® CANNABIS BREATHALYZER to help objectively determine recent use. The only tools available right now measure THC in blood, urine, and saliva, where it can remain long after impairment subsides. These tests were useful when cannabis use was illegal and the only data needed was to indicate the mere presence of THC in body fluids.

The HOUND® CANNABIS BREATHALYZER measures THC in breath, which indicates whether someone has consumed cannabis in the last few hours. Thus, even without laws specifically related to breath levels of THC, a measurement from the HOUND BREATHALYZER provides critical data about recent use which can help inform officers’ and employers’ decisions.

For historical context, alcohol breathalyzers were used well before per se limits were standardized. They provided useful information to law enforcement regarding recent alcohol use.


The study found that THC is reliably detectable in breath for 3 hours after smoking cannabis. By around the 3-hour mark, THC levels drop to virtually undetectable levels. The 3-hour timeframe is significant because NHTSA research has shown that this is the period of time in which people are most likely to be impaired after consuming cannabis. Other THC tests – urine, blood, oral fluid, hair – detect past use, well outside the window of peak impairment. With the legalization of cannabis, tests that detect past use become largely irrelevant to employers and law enforcement. The question is no longer whether someone has used cannabis at some point in the past, but whether they might be high at a given point in time. A test that has a very narrow window of detection provides the objective data needed to help make such a determination.

These results are significant for a number of reasons. They:

  1. Validate that THC is detectable in breath using Hound® breath capture technology during the peak window of impairment.
  2. Demonstrate the need for ultra-sensitive technology in order to measure THC throughout the 2-3 hour window of peak impairment after smoking.
  3. Confirm that breath is a better way to determine recency of use. Testing other mediums – oral fluid, blood, urine, hair – has not shown this ability to isolate recent use.
  4. Demonstrate that the Hound® breath capture technology enables researchers to conduct cutting-edge research to expand the frontiers of our collective scientific understanding of the effects of THC use.

Methods: In alignment with best practices for this type of research, the UCSF study included 20 participants – men and women who were a mix of frequent and infrequent smokers. Participants smoked cannabis they brought themselves. They smoked in a highly ventilated room designed specifically for smoking studies – completely separated from the research rooms to avoid any possible contamination. The research team collected breath and blood samples at 9 specified intervals throughout a 3-hour window after smoking.

All participants provided consent prior to joining the study. An Institutional Review Board (IRB) approved this research. The IRB reviews research conducted by UCSF clinical staff in order to protect subject rights and oversee subject welfare.


Hound Labs does not take a stance on cannabis legalization. We do, however, take a stance on driving or working under the influence: Don’t do it.