The contents of inhaled cannabis smoke indicate the extent to which the source material’s contents have been metabolized by our bodies (in other words, the bioavailability of cannabis upon smoking). Moreover, smoke comes with some health risks, which naturally makes cannabis smoke all the more interesting to scientists, doctors, and cannabis enthusiasts alike.
Up until 2019, the studies that had been performed on this subject were fairly rudimentary and one-dimensional, while having lots of variables—they explored only a couple of samples smoked in different conditions. 
That’s why a group of scientists  decided to undertake a more comprehensive and refined study, encompassing 12 cannabis samples (from police cannabis seizures in the North Island of New Zealand) within uniform smoking conditions.
“We selected cannabis samples, using limited information, to reflect different areas of [New Zealand], different growing conditions and different types of plant material.”
A smoking machine developed in house was used to smoke the joints and collect the smoke for assessment. They measured delta-9-tetrahydrocannabinol (THC) as well as other cannabinoids with gas chromatography-mass spectrometry (GC-MS). Furthermore, they calculated THC content in plant samples and collected total particulate matter (TPM) from the smoke.
Terpenoids turned out to be the most fluctuating component, with a 40-fold range of its contents. There were more terpenes in smoke with higher THC levels; they were mostly sesquiterpenes albeit with some monoterpenes. On the other hand, the authors note that THC delivery efficiency “remains consistent when the joints are smoked in a consistent way.” Specifically, median available THC value was 10.8% (ranging from 7.2% to 28.0%).
This means that almost 90% of the THC in a joint is lost through side-stream smoke, pyrolysis, and entrapment in the butt. THC formed a major component of the TPM. However, the values here ranged widely across samples (not correlating to THC) from about 15 mg/g to over 66 mg/g.
Ultimately, the “combustion and composition of cannabis smoke are not consistent between samples from varying sources.”  The composition of the cultivar determines the smoke.
- Sheehan TJ, et al. Chemical and physical variations of cannabis smoke from a variety of cannabis samples in New Zealand. Forensic Sciences Research. 2019;4(2):168-178. [Impact Factor: 1.531; Times Cited: 4 (Semantic Scholar)]