Later the same day, he brought in some photos showing evidence that he felt proved the reason why some houses older than 40 years had masses of dust in the ceiling void. He had removed 150 kilograms of dust from one house in Maroubra (south east Sydney) yet the house next door from the same era had a lot less dust in the void. The photos showed a coal gas burner in the bathroom of the "high dust house" with a flue pipe (approximately four inches in diameter) which, amazingly, had been vented into the ceiling void, rather than to the outside.

Apparently sometime in the 1950s coal gas was no longer supplied, but the burner remained along with the flue pipe to the ceiling void. His observation of a coal gas burner still in place allowed the ceiling dust contractor to finally work out why he had seen so many 4 inch diameter holes covered up in various ways (sometimes with a brick placed over them, sometimes plastered etc) leading from the bathroom or kitchen into the ceiling void in a number of homes with a heavy dust load in the ceiling. He thoughtfully collected a sample of the dust that was sitting in the flue pipe, and a further sample of dust from the ceiling void itself, to allow comparison of the levels of various elements after having them analysed at a reputable laboratory. See the Report of Analysis of Flue Dust and Ceiling Cavity Dust