Last week's fire at Eastown Timber left dust and debris on surrounding areas in Whanganui East, prompting one resident to give a sample to Horizons Regional Council for testing.
Bridget McArthur said her main worry was that some of it contained asbestos.
"The morning of the fire I could feel something dropping on my arm and at first I thought it was spitting.
"Then I realised it was probably fall-out. My car ended up covered in ash."
McArthur said some of the debris was red, fibrous material between 2cm and 12cm long.