If you smell burning plastic, it means that something is overheating. This could be an electrical appliance, such as a toaster or hair straightener, or it could be a wiring issue in your home. If the smell is coming from an appliance, unplug it immediately and call a qualified technician to check it out. If the smell seems to be coming from your outlets or light switches, shut off the power to that area of your home and call an electrician.