When you use the word “lab” do you mean a factory approved service center – or an actual labratory where an oder could be captured and analyzed?
Assuming you mean a typical electronic service center, I wouldn’t take their word for whether your drive has a problem or not. Most of these service shops are very busy and can’t devote much more time than hooking up the drive and playing a disc in it – while keeping an eye out for trouble from a dozen other devices they have also powered up that day – waiting for possible signs of trouble from any of them. If the technician is really good they may check the unit’s current draw against factory specs on the chance a component is failing and consuming higher than normal amperage in the process.
Quite honestly, unless your drive is malfunctioning, not working at all, or is visably discharging smoke, YOU are the best service technition at this stage. You can give it your undivided attention in its normally installed operating environment – conditions that most techs never get; hence their fairly high rate of missed correct diagnosis.
If earlier your drive made a smell, and that smell has diminished with the passage of time and hours of use, THAT is perfectly consistent with the “new electronic component smell” most new consumer electronic devices make. It smells for a few days and then goes away.
It is like the smell of a new car, new paint, fresh-cut lumber, and a million other things: they simply off-gas certain vapors until they have all evaporated, or otherwise had time to react with the ambient atmospheric gasses (in other words the air we breath – mostly nitrogen and oxygen) and forms a “skin” of sorts that gradually/significantly blocks off-gassing to the point of it not being noticable anymore.
Certain electronic components (like in your drive) get warm when in operation and this heat accelerates the off-gassing process. The more you operate the device the sooner the “smell” will dissipate. Perfectly normal. In the vast majority of cases (take my story from my previous post for example) if a electronic part is about to fail and is giving off a burned smell, IT WILL FAIL – [B]sooner[/B] rather than later. If the smell gradually diminishes, then the “later” has arrived and it didn’t fail so it is almost 100% certain to be functioning normally.
I really wouldn’t worry about that drive unless the smell gets stronger again and stays that way. And even if it did fail… so what? It smells a bit and then stops working. It is in a mostly metal case, located in a mostly metal PC case. It can’t start a fire. Your biggest problem is going through the @#^%@! warranty return process! :a
ADDED LATER: To answer your original question before I got carried away on the whole “drive causing smell” tangent, I think it is just the CD media you were using and not your drive causing the smell at all. You reported the same smell from these discs before and after a burn, and from more than one drive and PC; you didn’t notice the smell from your DVD discs. It’s the media and not your drive that you are smelling if the conditions of your first post are still correct.