The Scottish Fire and Rescue Service sent three fire engines and an environmental protection unit to the Clock in Cambuslang, Scotland, after the alarm was raised at 6pm on Sunday 2 February.
Fire crews conducted atmospheric monitoring tests while also ensuring the pub and nearby homes were also all evacuated.
A Police Scotland spokesperson said: “Emergency services attended at the Clock Inn public house, Main Street, Cambuslang, in response to a number of persons taking unwell within.”
Isolating the supply
Gas engineers from Scotland's gas distribution company SGN attended the scene and performed a safety check on the property and surrounding area.
SGN spokesman Waseem Hanif said: “A number of nearby properties were evacuated as a precaution but have now been re-occupied after we carried out a safety check.
“We made the situation safe by isolating the gas supply to the property.”
However, after following up with the public house on its Facebook page, a post read:
A spokesman for the pub also confirmed to the BBC there had been a carbon monoxide leak but said it was believed to have originated outside the building.
He explained the origin of the leak had not been confirmed but the pub had taken extra steps to make sure customers were safe.
A Scottish Fire and Rescue Service spokesperson said a total of seven people were given precautionary checks at the scene and firefighters ensured the area was made safe after.
No one suffered any lasting effects and none required hospital treatment.