This article is from Aug 2018, but is still valid. Many small manufacturers "mimic" the production process. Their in house does not allow for testing of final product for total content, VP and PG mixes may be used both for flavor and/or vapor content. Sometimes MCT oil is used. These are not good for vaping into the lungs!
Everything We Know About the Health Risks of Vaping CBD The problem many CBD vapers have faced recently seems to stem mainly from poor regulation over the vaping market in general, and the subsequent unreliable quality of any vape or vape oil.
Earlier this year, the United States Army issued a public health warning after medical centers at two bases in North Carolina saw some 60 patients within a few months for health issues that officials linked to their use of CBD vape oils. The symptoms included everything from headaches, nausea, and vomiting to disorientation, agitation, and seizures.