my house was built in 1948. the heater and hot water heater (all the same unit) is run with oil fuel. we have radiators in every room of the house. we have had the heater served yearly since we bought the house. unfortunately we have noticed soot on the walls and ceilings, and any white plastic in the house. could you tell me what could be causing this soot, is this harmful to my family, and what can be done to end the soot. thank you!