An inquest was held on Tuesday March 21, into the deaths of two people who died in Chelmsford.
Nikki Willis, 23, of Fox Crescent, Chelmsford, and Thomas Putt, 20, of Wren Close, Leigh-on-Sea, were found inside a Ford Fiesta on Monday December 5.
Sadly they died at the scene.
The inquest heard they died as a result of carbon monoxide poisoning and tests were carried out on the car, which found modifications had been made.
A coroner ruled their deaths were accidental.
Speaking after the hearing, Detective Inspector Rob Kirby said: “It is fair to say there was a unique series of events that came together to led to this tragic incident to take place.
“The combination of the modifications, the cold, still weather and the engine running whilst the car was stationary, all contributed to what happened that night.
“When modified, vehicles can produce significant quantities of carbon monoxide. This car was found to emit carbon monoxide levels 1,000 times higher than a factory standard identical vehicle.
“There are inherent dangers in modifying vehicles.
“Tom was not inexperienced, so even if you think you know what you are doing, this can still lead to unintended consequences.
“If you have carried out modifications on your vehicle, I urge you to satisfy yourself that these modifications are legal, and more importantly, safe, by consulting a qualified mechanic.
“Essex Police along with Tom and Nikki’s families want to ensure a tragic event like this can never happen again. Please have your vehicle checked. ”
DI Kirby has featured in a short video where he explains how a unique series of events came together to lead to this tragic incident:
— Essex Police (@EssexPoliceUK) March 21, 2017