The pair, both in their 30s, fell unconscious after being ‘overcome’ by fumes.
Alexander Forman, 32, and Richard Pooley, 36, were recovered from a four-metre deep pig manure tank at Newlands Farm, East Yorkshire on December 14 2015.
According to the two-day hearing at Hull Coroner’s Court, the pair had fallen into the pit after being ‘overcome’ by fumes.
Consultant pathologist Dr Richard Shepherd told the inquest both men had been fit and in good health. He found evidence of slurry in their airways and lungs.
“It is most likely that on descending into this tank that they became unconscious due to the lack of oxygen or high concentration of toxic gases," Dr Shepherd said. “That would have caused them to fall from the ladder into the slurry.”
The pair reportedly entered the pit after another colleague only partially unblocked the tank.
Mr Forman’s father, Robert, said it was a ‘standing instruction’ nobody should enter the pit under any circumstances.
He said: “I simply do not understand how they came to be in the pit.
“I can only assume there was some form of blockage and that contrary to practice one [of the men] has gone into the pit and the other went to attempt to rescue him without any thought for their own safety.
“Alexander was the most important person in my life. I built the business for him.”
The inquest is ongoing.