Current tests used by law-enforcement officials to detect marijuana use include blood, saliva and urine testing. But THC (the psychoactive component of marijuana) can stay in the system for days, or even weeks. With breath testing the THC signal only stays on a person’s breath for around four hours.

Driving while stoned is dangerous, no question. With increasing legalization of both medical marijuana and recreational marijuana, the problem has arisen on how to regulate its use and how to enforce the law. States like Washington and Montana limit THC levels to five nanograms per milliliter of blood, which is controversial. Pennsylvania has it limited to only one nanogram.

Every state in America has a driving limit for blood alcohol levels, as well as laws regulating drug use and driving. These laws are known as DUID laws which stands for Driving Under the Influence of Drugs. However, The National Highway Traffic Administration admits on its website:

It is difficult to establish a relationship between a person’s THC blood or plasma concentration and performance impairing effects … It is inadvisable to try and predict effects based on blood THC concentrations alone.

Detecting alcohol is easy because you’re looking for ethanol. Developing a breathalyzer for cannabis is underway with some companies, but is more difficult than it seems. One technology company claims that they are “working to develop drug-testing devices that will detect Tetrahydrocannabinol (THC- the psychoactive component of marijuana that causes intoxication) using breath samples. These devices would be used to provide detection of THC at roadside and identify drivers under the influence of marijuana”. They are trying to develop a hand-held, portable breathalyzer similar to a breathalyzer used for alcohol testing, which would be able to establish impairment at the roadside. But this technology may be more difficult to develop than it seems.

Adding to the complications is the different levels of impairment between states. Until science and policy surrounding cannabis advance beyond their present state, marijuana breathalyzers are probably not going to be used anytime soon.

Sources:
//www.nhtsa.gov/people/injury/research/job185drugs/cannabis.htm

//www.cbc.ca/news/canada/marijuana-safety-driving-1.3587636

https://www.google.co.za/?client=ubuntu#channel=fs&q=what+is+a+pot+breathzlyzer&gl=za