Ronnie Hazlett, 79, and his 44-year-old son, George, were both overcome by the fumes on the family farm on Ballyhanedin Road in June.
Both men were initially in a serious condition. Ronnie is now stable and at home.
However, George remains in Derry’s Altnagelvin Hospital in a stable condition.
He is still unable to speak or eat.
George was working with sheep in a shed where slurry was being mixed, the Belfast Telegraph has reported.
A young boy was also helping with the sheep and ran for help once George’s condition started to deteriorate.
Ronnie then rushed to help his son.
Mr Hazlett told BBC News NI: “I threw him over and started pressing on his chest,” Mr Hazlett told BBC News NI.
“I reached down and blew into his mouth. Then I went too. I don’t remember anything after that.
“I thought he was dead. That young boy played a very important role and so did the emergency services.
“It is a miracle we are alive.”
Mr Hazlett said farmers need to be aware how dangerous slurry can be.
“This all happened so quickly,” he added.
“I want all farmers to know that slurry needs to be treated with caution and there are many guidelines out there. Read them and read them again.
“It only took a matter of seconds for me to collapse.”
Ronnie also said that George fell in to a tank of slurry when he was six.
“He fell in and he couldn’t be seen. Then a hand appeared and we pulled him out.
“It was terrifying to see something related to slurry happen to my son again.
“It was scary. George just needs a lot of prayer now.”
A spokesperson for the Ulster Farmers Union (UFU) said: “Before working with or near slurry, take a moment to stop and think.
“Think about keeping animals and children well away when working with slurry.
“Think about the job you are going to do and make preparations to do the entire task safely.”
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