Disgusted patients say Feltham Health Centre should be condemned after fears of a gas leak forced them to be evacuated for the third time in a week.
They say the scare revealed the dangerous state of the building, with mums with babies, the elderly, the sick and medics hurried down the stairs from the third-floor surgery at around 9.45am on Tuesday.
Max Hutley, 81, was undergoing a hearing exam when he and his wife, Ruby, were told to leave.
He said: "It's ridiculous, you can't use the lifts, we'd been out 10 minutes and someone appeared using a zimmer frame. They had to come all the way down on their own. God knows what would have happened if there was a fire."
Patient Cynthia Everett, 73, said: "It's disgusting, an absolute disaster. There always seems to be something wrong here, gas leaks, fire scares. If something did happen there's no escape other than the stairs. It's dangerous, they should just condemn it and pull it down."
Feltham West councillor Barbara Harris, a member of Hounslow Council's health scrutiny panel, said:"They reckon there are safe areas but nowhere is safe in a fire. I'm going to raise it as urgent business at the next meeting on June 9.
"I have nightmares about it but unfortunately nothing will be done until something really awful happens."
Despite the scare, people were still allowed into Feltham Library on the floor below throughout the ordeal.
A spokeswoman for The Centre complex said: "This is the third time this week this has happened but the building is safe. The National Grid and Hounslow Primary Care Trust's contractors have declared it safe but there was a smell of gas and they were concerned about it. We were confident it was safe for people to continue using the other floors of the building."
Keith Dickinson, the PCT's associate director of corporate affairs, blamed managers at The Centre for the problems, adding: "The building is owned by the management company and as our landlords we would expect them to resolve this situation."