Dad lit up while connected to oxygen tank.
John William Nixon died after he was engulfed by flames, suffering burns to 80% of his body at his home in Llanaelhaearn, Gwynedd.
The 73-year-old lung and heart patient ignored warnings about not smoking near his oxygen tanks, which he needed to help him breathe.
On Friday his devastated widow Josie, 71, and daughter Christine, 42, wept as they recalled the tragic events at their stone-built cottage between Caernarfon and Pwllheli in August 2007.
Dr Andrew said long-term smoker Mr Nixon, a former carpenter and keen fisherman who needed a wheelchair to get around, died soon after being burnt "because he was not a well man".
Mrs Nixon, who was also her husband's full-time carer, said they'd begged him to stop smoking and hidden his smoking materials numerous times.
Mr Nixon was connected to oxygen tubes for 16 hours a day. Banned from smoking in his downstairs bedroom, he was allowed to smoke in the porch.
Recording a verdict of accidental death, North West Wales deputy coroner Nicola Jones said: "After hearing Mrs Nixon's evidence, it was an accident bound to happen."