Dr. Avery Gilbert, a scientist who specializes in odors, and Dr. Joseph DiVerdi, a chemistry professor at Colorado State University, studied the smell of marijuana.
They collected extensive air samples. First they took samples of the air inside the bags that held vacuum packs of marijuana, said Gilbert. Then Gosnell filled duffel bags with marijuana and DiVerdi took air samples from inside the duffels.
Back in their lab, they tested for concentrations of six terpenes, the compounds that give marijuana its odor. They ran the samples through a gas chromatography machine to separate and analyze the compounds.
The science backed up their supposition. The terpene levels were all too low to be detectable by people, said Gilbert.
Conclusion:
Marijuana odor is successfully trapped if the marijuana is packaged in double vacuum-sealed bags.
The science of smelling cannabis
Gilbert and DiVerdi then set out to test the human olfactory ability to smell marijuana in a laboratory setting.
They set up a standard experiment with a forced paired choice: a participant smelled two samples and had to choose which one contained marijuana. They used two different marijuana strains, one citrusy and pungent, the other earthy and herbal, according to the study.
They chose 4 different packing methods based on real life examples: Ziploc bags, thin plastic produce bags, pop-top canisters, and a vacuum-sealed heavy plastic bag inside another vacuum-sealed bag.
They also tested an open bowl with marijuana as a baseline. After filling the packages with marijuana, they left them in large buckets for an hour to let the odor accumulate and then asked the study participants to smell and choose.
21 people familiar with cannabis were blindfolded and individually tested on the 10 sample pairs.
The open glass bowl, the Ziploc bag, and the produce bag were all immediately identified by all of the participants. The dispensary-style canister yielded mixed results, but most people could still correctly identify the marijuana sample.
However the vacuum-sealed samples stumped participants. They did no better than they would have by flipping a coin, getting it right half the time.
“People would struggle,” said Gilbert. They went back and forth repeatedly between the two buckets to re-sniff.
It was difficult for a person to smell the double-sealed marijuana in a controlled test environment, Gilbert said, so what about the probability that an officer could smell double-sealed marijuana inside a suitcase in a closed partition from outside a car on the side of a highway?
That, he said, is “unlikely as hell.”
Original article
https://www.leafly.com/news/science-tech/can-police-really-smell-cannabis-car
One of their studies
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5798829/
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