The three people who died of suspected carbon monoxide in Cornwall have been named locally as John and Audrey Cook, and their daughter, Maureen.
Mr Cook, 90, his 86-year-old wife and their 46-year-old daughter were found dead along with a pet dog on Saturday in their static home near Camborne, Cornwall.
The alarm was raised when a neighbour tried to call in to help the elderly couple.
Devon and Cornwall Police are not treating the deaths as suspicious but it is thought a faulty appliance may be to blame.
Carbon monoxide is a colourless, odourless gas that claims around 50 lives a year and leaves some 200 people seriously ill.
Neighbour Julie Taylor told Sky News how, within hours of hearing of the tragedy, she went out and bought two carbon monoxide alarms: "It's just absolutely devastating.
"Having seen it in the neighbourhood and myself living on my own I went out straight away and bought them.
"It is frightening, you can't hear it, you can't see it, you can't smell it - it is the silent killer."
The Cook family had lived on the peaceful Tremarle Home Park for many years and were well known to neighbours.
Neighbour Andrew Stevenson said he was "very, very shocked".
Mr Stevenson was himself a victim of carbon monoxide poisoning in the 1990s when his chimney became blocked.
He told Sky News it was only his parents' decision to open a window that saved his life.
"I got out and we worked out eventually what caused it.
"It felt like someone had given me a head cold and then I got up in the early hours of the morning and it felt like somebody had rugby tackled me but there was nobody there."
He added: "You need to have a carbon monoxide tester even if it is a basic one."
Emergency services were called to the caravan park where they were living at lunchtime on Saturday after the couple's helper was unable to reach them.
Firefighters broke into their home and found the bodies inside.