Mr Grave was cutting a man's hair at his central Dunedin shop on Wednesday afternoon when he received a call from his alarm company that a smoke alarm had sounded in his house.
"I had to leave the guy's haircut and I was at my house in record time."
Low-lying sun had caused light to reflect from the magnified side of a shaving mirror, setting a dressing gown on fire and then the door, he said.
"It has made a bit of mess, but my house is safe and I am extremely grateful."
Southern Fire Region Fire Safety Officer Barry Gibson said low-lying sun had the potential to cause fires during the winter months.
"We had a case the other day in Invercargill of a single glass bead in a flower arrangement causing a fire, so people have to be aware that a fishbowl, mirror or anything with a curve in the glass can cause it to be magnified and pose a fire risk to your home."
One person aware of the danger of lower-lying sun is Dunedin Chief Fire Officer Dave Seque.
Earlier this year, low-level sun caused vertical blinds at his house to be scorched, after sun reflected back to the open blinds from a mirror on the floor.
"It was a reminder that you can't leave objects, such as concave mirrors and glass objects around," he said.
Despite scepticism about low-lying sun as a cause of fire, it was a real threat that people should be aware of, he said.
