The pair, who were in their 50s, were found in their armchairs at home at 10:30 GMT on Sunday.
An ambulance spokeswoman said the incident may have been due to a possible gas leak at the property in Wickford.
Essex Police are treating the deaths as unexplained. The house remains sealed off for investigation.
Emergency services were called to the house by the couple’s sons who discovered the pair.
A hazardous area response team was sent to the scene as it was thought carbon monoxide may be involved.
The deaths are not being treated as suspicious, a police spokesman said.