Precise vapor pressure measurements reveal THC, CBD, and CBN are predicted to exist primarily in the vapor phase of exhaled breath, meaning current aerosol-only breathalyzers may be missing most of the signal.
Breathalyzer developers, forensic scientists, law enforcement, and traffic safety researchers
What the researchers found
Vapor pressure measurements extrapolated to body temperature predict all three major cannabinoids (THC, CBD, CBN) reside primarily in the vapor phase of exhaled breath, potentially explaining the large variability seen in aerosol-only collection devices.
Why it matters
Cannabis breathalyzers are being developed worldwide but show inconsistent results — this fundamental chemistry data explains why: devices capturing only aerosol may miss most of the cannabinoid signal in exhaled breath.
The numbers in context
Vapor pressures (364-424K): THC 0.046-7.83 Pa, CBD 0.083-13.44 Pa, CBN 0.020-5.68 Pa; measurement uncertainty 2.9-9.5%; all three cannabinoids predicted to be primarily in vapor phase at breath temperature.
How the study worked
Gas-saturation apparatus measurements of vapor pressure for THC, CBD, and CBN from 364-424K, extrapolated to body temperature via thermodynamic correlation, with vapor-aerosol partitioning modeling of exhaled breath.
What this study cannot tell us
Extrapolation from higher temperatures introduces uncertainty; breath composition varies between individuals and with environmental conditions; pure compound behavior may differ in complex breath matrix.
How to read the evidence
High-precision physical chemistry measurements with thorough uncertainty analysis, published in a breath research-specific journal, though predictions require experimental validation.
When this study was published
Published in 2026, providing fundamental data needed to advance cannabis breathalyzer technology.
The bigger picture
This could redirect the entire cannabis breathalyzer industry — if cannabinoids are mostly in vapor form during exhalation, current aerosol-focused devices need fundamental redesign.
Questions still open
- Will next-generation breathalyzers capture both vapor and aerosol phases? Could vapor-phase detection actually improve breathalyzer reliability and reduce the variability problem?
Common questions
Why are cannabis breathalyzers unreliable?
Is a cannabis breathalyzer possible?
Read the original research
Vapor pressure measurements on Δ9-tetrahydrocannabinol, cannabidiol, and cannabinol to inform cannabis breathalyzer development.
Journal of breath research, 20(1)
Citation
Beuning, Cheryle N; Berry, Jennifer L; Paulechka, Eugene; Huber, Marcia L; Jeerage, Kavita M; Widegren, Jason A; Lovestead, Tara M. (2026). Vapor pressure measurements on Δ9-tetrahydrocannabinol, cannabidiol, and cannabinol to inform cannabis breathalyzer development.. Journal of breath research, 20(1). https://doi.org/10.1088/1752-7163/ae3794