My basement oil furnace has little black dots of soot on the pipe to the chimney , floor and top of furnace. Basement has a strong soot smell. How can I fix this problem? The oil furnace is running, but it doesn't sound as strong or clear. (Soot - Black substance formed by combustion or separated from fuel during combustion, rising in fine particles, and adhering to the sides of the chimney or pipe conveying the smoke )