The road was closed between Broughton and Chester after an acetylene cylinder exploded through a garage roof and flew about 70 metres into the air over Meadow Cottage on Roughlyn Crescent, Marlston-cum-Lache on the Flintshire-Cheshire border.
Another cylinder of acetylene, which is extremely flammable, flew about 30 metres from the garage into the garden of the property.
Workers at Chester Business Park described hearing the loud bangs at about 4pm on Friday.
Watch manager Steve Newton, from Chester fire station, said that the residents in the cottage were lucky that the cylinders did not explode into the property.
"There was the potential for a few fatalities," said Mr Newton, "It is just sheer luck that nobody was hurt."
It is believed that the two cylinders, weighing 20-30lbs, ignited after a car caught fire in the garage of the property.
The A55 was closed in both directions between the Post House roundabout near Wrexham Road and Broughton because of thick black smoke billowing across the carriageway.
A 250-metre cordon was placed around the area because there were other gas cylinders in the garage which could have exploded.
Mr Newton said: "Cylinders are like unexploded bombs and we had to cool them down for 24 hours after the fire.
"Cylinders are very unpredictable and could easily have hit people.
"People were more lucky that the cylinder went over the top of the house rather than through the house."
Some residents of Roughlyn Crescent were evacuated and the road was closed from the time of the incident until about 3pm on Saturday.
Residents who were not able to return to their homes stayed in a hotel or Lache Community Centre for the night.
The A55 was closed until about 8.30pm, causing severe traffic congestion, with reports that it was backing up to Manchester.
Carys Woodward, her partner, Damien Gray, and their baby, Kai, aged five and a half months, had to wait to return to their home on Roughlyn Crescent.
Carys said: "We were in town and the taxi had to drop us off at the roundabout (in Roughill, Marlston-cum-Lache) because the road was cordoned off. We saw black smoke."
Damien added: "We thought it was our house. A neighbour rang us to say that their garage door had been blown off with the explosion. I'm quite shocked."
Two fire engines from Chester, one from Ellesmere Port and the Hazmat unit from Warrington were at the scene.
Firefighters stayed at the area for 24 hours to cool the remaining cylinders.
Today staff from the British Oxygen Company (BOC) were due to remove the cylinders from the area.
Did you hear the explosions, or take any pictures of the incident?
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