How Does a Cannabis Breathalyzer Work — Can It Measure Impairement?

How Does A Cannabis Breathalyzer Work?

With the unstoppable force of the cannabis industry, society is gearing up for full-scale legalization. One of their biggest concerns is ‘drugged drivers’. While the statistical evidence suggests that there is no real uptick in fatal traffic collisions post-legalization, these concerns are still a major problem for society to solve.

In comes the cannabis breathalyzer. Similar to an alcohol breathalyzer, the cannabis breathalyzer would test for acceptable THC levels within a user to determine whether they are high or not. The only problem is – there is no functional (standardized) cannabis breathalyzer available on the market because cannabis interacts with everybody differently. Furthermore, there are little to no breathalyzers as effective to judge impairment

The amount of THC in someone’s bloodstream would have little to no indication of how ‘high’ someone is. This is because THC can compound over time and while a user might have high levels, it doesn’t indicate how impaired they are.

However, this doesn’t mean researchers around the world aren’t trying to crack the problem surrounding cannabis breathalyzers.

cannabis breathalyzer


How Does a Cannabis Breathalyzer Work?

Well, to fully understand or even speculate on this, we would need to understand the current working technology of an alcohol Breathalyzer.

Alcohol Breathalyzer

An alcohol Breathalyzer makes use of either an oxide, fuel cell sensor or a spectrophotometer which are the most commonly used technologies. The best Breathalyzers combined two of these technologies making them the most accurate of breathalyzers.

Scientifically,  When you breadth into the Breathalyzer, the ethanol in the breath, if any, is oxidized and turned into acetic acid. (This then is the purpose of the oxide sensor). The next reaction occurs at the cathode where the amount of oxygen in the Breathalyzer is reduced by adding water to oxidized ethanol. This causes an electric current to be produced which then triggers the Breathalyzer and measures the level of alcohol in the person’s blood.

This particular technology is hard to use on cannabis users, as very little of tetrahydrocannabinol (THC), the active ingredient in cannabis, is left on the breath, thus giving back-up to claims that the cannabis Breathalyzer is not 100% effective..

Are cannabis Breathalyzers used at the moment?

The argument behind how a cannabis Breathalyzer should work

THC Breathalyzer

While there are currently aren’t workable prototypes on the market, the theory is pretty solid. As opposed to the current ways of detecting THC in a user’s system, a THC breathalyzer would provide insight into recent cannabis behaviour.

This is because cannabis can be detected in the breath for up to four hours (in heavy users) and 2 hours (in moderate users) after consumption. This provides us with a smaller window into the “impairment” of cannabis.

Considering that the peak of a cannabis high would last between 2-3 hours, it would be relatively safe to say that having cannabis in the breath is an indication of recent consumption.

Measuring it, however, provides more difficulties. The vapour pressure of THC in the breath is quite low, however, it is estimated that it is 100 million times less than ethanol’s vapor pressure. This means that a THC breathalyzer would need to be much more sensitive than an alcohol breathalyzer.

Irrespective of whether companies like HoundLabs can develop a functional cannabis breathalyzer, it would provide a small window to determine the impairment of drivers.


It takes approximately an hour and forty minutes for the THC concentration to drop by 90% in the system of a user.


This means that if someone were to test positive on a cannabis breathalyzer, it would suggest that they smoked within a 2-hour window prior to being tested.

Considering it takes about 2-3 hours for a user to ‘sober up’ entirely, the development of a cannabis breathalyzer is actually not a bad idea.

Are there active cannabis Breathalyzers?

One California company, HoundLabs, has indeed developed a cannabis Breathalyzer. They claim it can detect the presence of THC less than two hours prior. The HoundLabs Breathalyzer contains disposable cartridge to avoid having to dispose of the whole breathalyzer. It also ensures that the officers collect the samples without having to come into direct contact with any oral fluid.

How does it work?

  • First, it captures the breath
  • Processes the breath
  • Then gives results
  • It allows you to print out the results

This nifty device is said to hit the road by winter of 2018.


Final Thoughts

Many people are opposed to the idea of a cannabis breathalyzer, however, it’s not something that should be feared. Nobody wants impaired drivers on the road, whether you’re smoking a joint or drinking a beer. You’re sitting on a ton of metal that can move at high velocities. It’s important to have all your senses on point.

A cannabis breathalyzer would provide society with a fixed threshold to ensure that we limit the number of impaired drivers on the road.

Additionally, cannabis users can rest assured that the joint they smoked last night, won’t deem them ‘impaired’ the day after. This is a win-win for both the state and the individual.

See also:

Can You Donate Blood If You Smoke Weed?

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