A 55-year-old found dead in his garage in St Albans was killed by carbon monoxide poisoning, an inquest has heard.
Police attended the home of Ralph Parrett, of Frogmore, when neighbours reported they hadn’t seen him in "a while".
Officers broke through the chained front door to force entry to the property on Radlett Road on March 13 but found no sign of Mr Parrett.
After conducting a search of the house, police discovered a note left in a small box by the deceased in which he said he was going to "end it all".
The note made reference to his car.
Police then forced entry to the garage and found Mr Parrett dead on the driver seat of his vehicle.
At Hertfordshire Coroners Court, senior coroner Edward Thomas said there was no way of ascertaining how long he had been dead for.
A post-mortem was carried out by Dr Matilda Ralph, pathologist, at Hemel Hempstead Hospital.
It revealed Mr Parrett’s carbon monoxide levels were above a lethal level.
Mr Thomas said: "Police found a small box with a short note inside indicating he could no longer live.
"The scenes of crime exam did not reveal any third party involvement in the death.
"The cause of death was asphyxia by carbon monoxide poisoning.
"Carbon monoxide present was 69 per cent , well above the lethal limit."
Mr Parrett had lived alone after his mother died in December 2012.
The inquest heard Mr Parrett had a history of high blood pressure and diabetes.
He suffered a stroke in March 2003. During the investigation police found Mr Parrett had lost contact with his GP in November 2013.
Mr Thomas continued: "I am satisfied by the evidence that this was a deliberate act that caused his death, and that he knew what he was doing and that’s what he wanted.
"It is my determination that he took his own life.
"I cannot say for certain when he died, so I will record that he was found dead at his home on March 13."