A service is being held at Glasgow Cathedral to mark the 40th anniversary of a blaze in a warehouse in the city in which seven firemen died.
They were killed by a flashover - a burst of flame and intense heat up to 1,000 degrees - as they attempted to rescue a trapped colleague.
The incident happened in Kilbirnie Street on Glasgow's Southside in 1972.
The service followed a ceremony which rededicated a memorial to the firemen in Glasgow's Necropolis.
The event was attended by families, friends and colleagues of the dead firefighters.
In an address at the cathedral, Strathclyde Fire and Rescue Service Chief Officer Brian Sweeney paid tribute to the victims of the tragedy.
He said the deaths were "a severe blow" for a service which had not fully recovered from the Cheapside Street Disaster, a whisky bond explosion that killed 14 firemen and five members of Glasgow Salvage Corps in 1960.
Recalling the Kilbirnie Street tragedy, Mr Sweeney said: "Press photographs taken at the scene show the strained and anxious faces of firemen donning breathing apparatus after if had been confirmed by Deputy Firemaster Peter McGill that a search was continuing for 'firemen believed missing, number at present believed to be seven'.
"The shock was also experienced back at the fire stations where control room operators had despatched appliances to the fire."
Mr Sweeney said the people of Glasgow had been shocked by the second major fire service tragedy in 12 years and a huge crowd lined the streets as hearses bore the bodies of the seven men to Glasgow Cathedral for the funeral service.
In his address the chief fire officer also pointed out that it was the last time that Kilbirnie Street would be commemorated under the banner of Strathclyde Fire and Rescue.
He continued: "As we ponder the sacrifices made at Kilbirnie Street and Maryhill Road and at other incidents where firefighters have lost their lives, many of you, particularly close family members of those who died, may be asking yourselves what happens next year when the Scottish Fire Service is established?
"You may wonder whether the new service will have time to remember its past while it plans for its future.
"We need only wander round the Necropolis to see how many of the people who were once the great and the good of Glasgow have since been reduced to fading names on Victorian monuments and gravestones.
"The Necropolis, which was opened in 1831, was intended to be the last resting place of Glasgow's most distinguished citizens.
"Over the years a total of 3,500 monuments were erected by proud families of the deceased. How many of those families still remain? How many descendants make a pilgrimage to the graves of those who helped make Glasgow the Second City of the Empire?"
He added: "I cannot answer that question but I can assure the families of the firefighters whose names are on the memorial that as long as there is such a thing as a Fire Service Family, those firefighters will always be remembered."
The Kilbirnie Street fire took place at the Sher Brothers' cash and carry warehouse.
Six of the firefighters entered the building to rescue a seventh colleague who had been trapped by falling debris.
They were all killed when the fire suddenly transformed into a raging inferno.
Their names were inscribed in the Fire Service Memorial at the Necropolis, which had been erected in 1960 to commemorate the Cheapside Street whisky bond explosion.
Last year the monument was refurbished and the names of the seven Kilbirnie Street victims and four victims of other tragic incidents were inscribed prominently.
The refurbished memorial was unveiled on Saturday by Glasgow's Lord Provost.