The question of whether simply inhaling the scent of cannabis can lead to intoxication is common, especially as cannabis use becomes more visible. The distinct aroma leads many to wonder if they are absorbing the same compounds that cause a “high.” The answer requires separating the sensory experience of the odor from the chemical absorption required for intoxication or a positive drug test.
Odor Versus Psychoactive Compounds
The powerful and recognizable scent of cannabis comes primarily from a group of aromatic compounds called terpenes. These volatile organic molecules are produced by the cannabis plant and are also responsible for the distinctive fragrances in plants like pine, citrus, and lavender. Recently, scientists have also identified volatile sulfur compounds (VSCs) that contribute to the pungent, “skunky” notes, even in very low concentrations. These fragrant compounds are non-intoxicating and are the reason you can smell cannabis from a distance.
The psychoactive effect, or the “high,” is caused by tetrahydrocannabinol (THC), a cannabinoid, not a terpene. In its pure form, THC is odorless, meaning the compound responsible for the high does not contribute to the plant’s scent. Intoxication requires THC to be heated and released into a smoke or vapor, which is then absorbed through the lungs into the bloodstream. Simply smelling uncombusted cannabis or ambient odor does not transfer enough THC to cause psychoactive effects.
Secondhand Smoke: The Likelihood of Intoxication
While the simple odor of cannabis will not cause intoxication, the presence of actual secondhand smoke introduces the psychoactive compound THC into the air. Studies have explored the conditions under which passive inhalation of this smoke can lead to a measurable effect on a non-user. For a person to experience any mild intoxication, the exposure must occur under extremely specific, concentrated conditions. This scenario typically involves being enclosed in a small, unventilated space, such as a vehicle, with multiple people actively smoking high-potency cannabis for a prolonged period, often an hour or more.
Under these “worst-case scenario” conditions, non-smokers in research settings reported mild effects, such as pleasantness or tiredness, and minor cognitive impairments. When the same experiment was conducted in a well-ventilated room, passive subjects reported no effects other than increased hunger. This demonstrates that ventilation level is a significant factor in determining airborne THC concentration. Therefore, casual exposure, such as walking past someone smoking outdoors, is biologically implausible to cause intoxication.
Can Passive Exposure Cause a Failed Drug Test?
A secondary concern regarding secondhand cannabis smoke is the possibility of failing a workplace drug test. Standard urine tests look for the metabolite THC-COOH, not the active THC compound, and use specific cut-off thresholds to screen out passive inhalation. The most common cut-off for initial screening in the Federal Workplace Drug Testing Program is 50 nanograms per milliliter (ng/mL) of THC-COOH.
In extreme exposure studies, researchers found that trace amounts of THC and its metabolites were detectable in non-smokers’ blood and urine, but breaching the 50 ng/mL cut-off was rare. In one study, only a single non-smoker out of six tested positive at the 50 ng/mL level four hours after the unventilated, high-potency exposure ended. While more sensitive cut-offs (e.g., 20 ng/mL) resulted in multiple positive tests, the 50 ng/mL standard is set precisely to prevent false positives from passive exposure. Failing a standard drug test from casual or brief exposure is highly unlikely, as it requires the same extreme, unventilated, and prolonged conditions necessary to feel an intoxicating effect.