We are coming to the end of a splendid period of weather, which will help the winter along nicely. Unfortunately soot is hygroscopic (tending to absorb moisture from the air). To be able to remove soot effectively from your chimney the sweep needs the soot to be dry. Therefore at this time of the year, after a prolonged spell of disuse, it is important to have a few small fires before the sweep calls. It is easy to establish that the chimney is not blocked without lighting a fire to find out! On an open fire simply dangle a single sheet of paper in front and observe it being drawn up the flue. For a stove a similar approach is sometimes possible, otherwise a hand placed near the top of the throat plate/baffle plate will identify the movement of air. A single sheet of paper burnt in the fire will confirm things one way or the other. This can also be checked with a lit joss stick, a match or lighter. If you light a single sheet of paper as close to the bottom of the flue as possible just before lighting the proper fire, which you have previously laid, you may start the movement of warm air up the chimney, which the smoke will then follow.
Damp soot will not burn! It has to be very hot to catch fire! Be not afraid!