Ive been running various brand heat cords for around 10+years. They mostly look like they come from the same factory and all compluy to Australian Standards. If you are sealing one under a tiled floor then you dont have to much to worry about. I dont recommend you do it these days but we used to take the cord out of old electric blankets. The plastic coating wasn't anywhere up to the standard of todays heat cord. Test it regularly though. I have had one go live after years of stretching from being cleaned.
