The sweep before breakfast

Text 1: Half past five, by Eliza Thornbury

An original autobiography written in a nineteenth-century voice; a period simulation, not an archival document.

The sweep knocked at half past five, while the street was still dark. My mother had been up since four, letting the kitchen fire die and laying old sheets over the dresser and the chairs. He brushed the flue from below with rods that he screwed together one length at a time, pushing them higher until the brush appeared above the chimney pot, where his boy waited in the road to shout that it was through. By half past six he had bagged the soot and gone on to the next house on his list, for once the neighbours woke, every grate in the row would be lit for breakfast and no chimney could be swept until night.

Explain why the sweep started work so early in the morning.