It is not the brake pads but it is some what for the motor to make a hot smell with a heavy load and even the transmission heats up a little and can produce a warm oily smell. It is not likely anything to worry about, but as with any major gas or electrical appliance do not keep combustible items around or on top of any machine that is hooked up and used. That means no paper or plastic bags shoved in the space between the refrigerator and the wall etc. Yes even refrigerators can start fires I have seen it happen, we had a customer with a 1970s GM Frigidare that keep her paper shopping bags there and the house burned to the ground. If the bags hadn't been there she would have only had a little smoke from the shorted and burnt compressor relay.