Firefighters in full breathing apparatus had to evacuate the homes in Barrland Street, Pollokshields, after several carbon monoxide alarms were triggered.
It is understood an idling engine, possibly a generator used by workmen, caused the alert, which lasted two hours.
Nouria Zahir, 28, who was at home with son Iman, 2, said firefighters in full gear came to her door and told her to get out the building.
She said: "The firefighters were really good. They said we had to get out because there was a gas leak.
"I came out with Iman and we waited. They then checked the house."
Her husband Abdul, 42, arrived on the scene after receiving a call from his wife.
He said: "My wife had a headache all day from about 8am. She phoned me to say the fire service was here and I came home. When I first saw the fire engine I was worried there was going to be an explosion or something."
His cousin, Farzad Vesmell, 14, had also arrived at the time of the alert to pay his family a visit after school.
Farzad said: "I arrived and saw all the fire guys, so it was scary. I was worried about what was happening and whether my family was safe."
Strathclyde Fire and Rescue said eight firefighters wearing full breathing apparatus cleared a "large number" of flats over two communal closes in the street.
Two appliances from Polmadie and one from Maryhill Community Fire Stations were at the scene, with the service's Environmental Protection Unit also mobilised.
A fire service hazardous materials officer and a scientific adviser from Glasgow City Council were also called in to conduct atmospheric tests.
The alert happened at about 2.25pm and residents were allowed to return to their homes about 4.30pm, following confirmation the atmosphere was safe.