Desperate tenants said a mum was trapped in an unreliable broken down lift for more than two hours with her baby.
Neighbours at Trident Point, a block of flats surrounding Morrisons supermarket in Pinner Road, Harrow, began to worry about the level of oxygen in the elevator stuck on the first floor.
Firefighters who are members of the Fire Brigade Union were on strike yesterday and did not attend the emergency and the block's managing agents have both been notified.
An engineer arrived at about 4.40pm to release the mother and child after several calls.
Eyewitness Shabana Ishaq, 43, whose brother and mother live on the sixth floor, said: "We have got a mum and her baby in there for an hour in the lift.
"She said there's no power in the lift. She's tried the engineer's call button and it isn't working.
"There's no mobile phone reception either."
Trident Point was only built just over two years ago and different blocks are looked after by different managing agents.
Ms Ishaq said: "The lifts are regularly breaking down.
"Management said they've called out the engineer but it's been about one hour already.
"There are two lifts. One has been vandalised and they have got a part coming from Italy - this is what I have been told - the other breaks down all the time, and we have got people here with knee problems and asthma and they're going up and down the stairs instead."
Tenants had called a meeting today with the managing agents about the lifts before yesterday's incident unfolded.
A London Fire Brigade spokesman said: "The brigade's policy whether there is a strike or not is that it is the building owners' responsibility to get contractors or lift engineers out to get people from faulty lifts."
Harrow Police said they could find no record of a call about the incident.
n We stated in earlier versions of the story that the lift affected was in the block run by Metropolitan Housing Trust but was incorrect. We apologise to the trust for the error.