The manufacturer of cookers linked to five deaths in Cornwall was not aware of the risk of them emitting carbon monoxide if used with the grill doors closed, an inquest has heard.
Two people died in 2010 and three members of another family died in 2013.
The inquest heard all of them had used gas cookers produced by the parent company of Beko.
In a statement, the company said product safety was its “primary” consideration.
Kevin Branton, 32, and Richard Smith, 30, died in 2010 in Saltash, while Maureen Cook, 47, Audrey Cook, 86, and Alfred, known as John, Cook, 90, died in 2013 in Camborne.
Opening the inquest, Coroner Geraint Williams said post-mortem examinations showed all five died from carbon monoxide poisoning.
In a statement to the inquest, Alp Karahasanoğlu, from Arcelik, the Turkish parent company of Beko, said appliances were subjected to rigorous internal testing before being tested externally.
He said safety testers aimed to anticipate ways in which customers might misuse a product but that it was “not always possible to see into the minds of the end user”.
“No-one foresaw the possibility that the grill might be used with the grill door shut, contrary to the advice in the user manual,” he said.
Mr Karahasanoğlu said the reason for this advice was for the efficiency of the grill and not to prevent the build-up of carbon monoxide.
“No-one at Arcelik was aware of this risk until these tragic deaths came to our notice,” he said.
The inquest heard in a statement the Department for Business, Energy & Industrial Strategy first became aware of five fatalities linked to the use of gas cookers with grill doors closed in early 2009.
Those deaths in Kent, Doncaster, Ireland and Northern Ireland prompted the department, then known as the Department for Business, Enterprise and Regulatory Reform, to call for an amendment to the safety standards covering gas cookers.
The inquest continues.