I light a candle before going to bed at night. The next day, there was a lot of black ash in the room and black ash in the nose. This is the problem.

The main components of candles are hydrocarbons with relatively large molecular weight, such as cycloalkanes and aromatic hydrocarbons. When these substances are not completely burned, there is residual carbon. During combustion, the hot air flows indoors, and a part of it falls after cooling. When breathing, some air containing carbon particles is inhaled, which is blocked by the hair in the nasal cavity, so there is black ash in the nose and throat.