I have a copy of the curriculum and have taken many of the classes needed to become an arson investigator in the state of Georgia. I can tell you I have fought several fires where glade plug ins were still in the walls of homes that caught fire. There was no evidence they caused the fire, most are melted to the point of no recognition but it was blatently obvious it started somewhere in the wall, or a different room. Plastic melts at a low temperature. With no evidence a glade plug in was not be to blame. I personally, have seen case studies where investigators have said it was the cause, but after independent studies of more experienced investigators, scientist, electrical engineers, etc have completely ruled it out. All studies were around the rumor era of the circulating emails where the fires "could have been" caused by plug ins. Most of the time it is faulty wiring. Loose connections, faulty recepticles, etc. Most fires truly are ruled undetermined unless it was witnessed or contained to the point of orgin. I haven't seen or heard of a report of a plug in being the cause in years. If it was it would be back in the news or on fire engineering websites.
Sadly in our line of work it is easy to pin blame without being 100% accurate. In fire investigations the investigator can say anything he or she is challenged. Some of the best investigators can suspect arson, etc but lack the skills of proving their case and many fires are ruled undetermined or a different cause.
For now ill keep fighting fires and doctoring up sick people and leave the cause and determination to someone else.