If you wait until fall, soot deposits will harden, making removal more difficult and increasing the risk of fire.

In 1955, he sent her a sample of his company's wallpaper cleaner - a doughy substance that people rolled up and down their walls to remove soot deposits.

Studies revealed that in 1926, St. Louis had an annual soot deposit of 870 tons per square mile, far above Chicago and Pittsburgh.

Chimneys should be inspected and cleaned at least once a year, preferably in early spring before soot deposits have hardened.

Some homeowners hold this off until the fall, but by then, soot deposits may harden and cleaning will be more difficult.

At the same time the bronze railings will be removed, cleaned of soot deposits and coated with wax.

The only problems found with the flight were that the LES rockets had left a soot deposit on the spacecraft exterior and the stability of the spacecraft was less than predicted.

People have brought their cars to my advice surgery to show me burnt paintwork caused by soot deposits.

Critics, however, questioned whether the soot deposits were left by a single, global fire or were the accumulation over many years from many smaller fires.

"And it's not unusual for us to see soot deposits of a quarter of an inch or more."