Contact highs comments are common, with a lot of people claiming lightheadedness when near people who are smoking cannabis.

The smell of weed can sometimes make you feel like you’re high, especially when in a closed environment, such as a weedy dorm room or a packed concert. But can people really get high without smoking or is this more of a mental thing?

Contact highs cause a lot of stress for people, making them wonder if they could fail a drug test or get high without meaning to. Luckily, experts know some of the answers to these questions.

A study conducted in 2015 ran two experiments where cannabis smokers and non smokers were put together in a room. In both scenarios, the smokers smoked around 10 joints each and sat around a table, surrounded by nonsmokers. The difference between the two experiments was the ventilation of the room; the first experiment had regular ventilation and the second had none at all. Results showed that nonsmokers from the second test showed some presence of THC in their urine and blood samples.

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“Exposure to second-hand cannabis smoke in an unventilated chamber the size of a small room produced minor increases in heart rate, mild to moderate subjective drug effects, and minor, but detectable, levels of performance impairment on some behavioral/cognitive assessments,” wrote researchers. These results weren’t reflected in the first round of experiments.

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Despite the popularity of shotgunning, it turns out that second-hand highs are very hard to stumble upon. When people smoke weed and exhale it, only a very small amount of THC comes out. With no detectable amounts of THC, there’s no high for the bystanders to pick up on and get high from, especially when located in a room momentarily or with a normal amount of ventilation.

In conclusion, it’s pretty hard to get high off marijuana if you’re not an active participant.