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The deadly blaze at the 24-storey Grenfell tower block in west London has shocked the UK. Fire services around the world have to deal with blazes in high-rise blocks, so what lessons have been learned?

Firefighters arriving at the scene of a high-rise fire would normally set up a base about two floors below the actual fire, says Bob Parkin, an ex-firefighter turned safety consultant.

This allows them to set up entry control points, so firefighters going to fight the blaze can be recorded, and crucially, have their breathing apparatus checked so it's clear how much time they can spend in a dangerous, smoke-filled area.

The amount of time each person can spend fighting the fire is limited by the amount of air available - so any minutes spent climbing up into a building with equipment is precious fire-fighting time wasted.

"You're going to use a considerable amount of air going up the 10 floors, so because of that and various other things, they will set up the control point two floors below the fire," Mr Parkin says.

Once they are able to go in, the immediate focus, if people are reported to be trapped in the building, would be on rescuing them, rather than firefighting, and the firefighters would carry minimum levels of equipment for that reason, he adds.

"They will have to fight their way in, in some instances, but they will take chances when people's lives are at risk, without a doubt."

But the situation faced at Grenfell Tower in London would have been extremely difficult, Mr Parkin says, because the fire was able to spread so rapidly, and appeared to engulf nearly the entire building.

Having to get 20 storeys up to rescue people in that situation "is just unbelievable", he says. Without extra air supply for the person rescued, the journey back out of the building would be extremely dangerous.

The fire brigade would also have had to operate from a very low level in the building because of how far the blaze had spread, and there were concerns that the building might collapse.

Still, London's firefighters "didn't waver", London Fire Brigade commissioner Dany Cotton said. "They were going through there time and time again battling through the floors looking for people."

Roy Wilsher, chair of the National Fire Chiefs Council and a firefighter of 35 years' standing, said fire crews were confronted by terrible scenes.

"You turn the last corner and see something like that in front of you... it makes you go into almost automatic pilot," he told ����ý Radio 4.

Fire safety experts say the cladding used on Grenfell Tower is the likely reason why the blaze spread so quickly - making it impossible for the fire to be contained floor-by-floor.

According to Mr Wilsher, firefighters did eventually reach the top floor "but it took them hours to get there".

In Dubai, recent high-rise building fires, including at the 79-storey Torch Skyscraper in 2015, spread because of cladding, according to fire engineering consultancy Tenable Dubai.

But these fires caused no fatalities because the design and construction of the buildings allowed firefighters to battle the blaze and residents to evacuate via smoke-free, fire-free safety zones, it says.

"All the fires here lasted for six or seven hours but occupants managed to evacuate successfully and all fires were extinguished with no loss of life," says Sam Alcock, the firm's director.

"In my opinion, design and construction is what saved lives."

Residents in Grenfell Tower had previously been advised to stay inside their flats in the event of a fire, and Ikhwan Razali, a fire engineer with Tenable understands why.

"You can advise people to stay in place if you have good fire suppression between levels, but in this case [in London] the advice appears to be wrong."

Recent large blazes around the world

Plasco building, Iran, January 2017: A fire at a 17-storey commercial building in the Iranian capital led to multiple deaths, including 18 firefighters. The building collapsed - it had been deemed unsafe prior to the incident.

Baku, Azerbaijan, May 2015: 16 people died in a fire in a residential building, including five children - cladding on the outside of the building was blamed for the way the fire spread.

The Torch, Dubai, February 2015: Fire swept through one of the tallest residential buildings in the world. Hundreds of people had to be evacuated from the 79-storey skyscraper.

Krasnoyarsk, Russia, September 2014: A 25-storey tower block was destroyed by fire. All 115 residents fled the building and there were no reported casualties.

Shanghai, China, November 2010: A fire in a 28-storey tower block killed 53 people and injured at least 90. Chinese state media reported that unlicensed welders were blamed for the accident.

Tower cladding 'linked to other fires'

In high-rise building fires, aerial platforms can be used to allow firefighters to operate from outside the building. But the London Fire Brigade's aerial platform vehicles can only reach heights of about 32m - limiting how high up the blaze can be fought.

In Dubai, where skyscrapers like the Burj Khalifa reach more than 160-storeys, they have higher aerial platforms of up to 80m, Mr Alcock says. But building in access for firefighters to safely get high up in tall buildings, including via special lifts, is crucial.

Why are people told to 'stay put'?

Six questions for the investigation

Residents of UK tower blocks like Grenfell Tower whose flats are not affected by fire or smoke are usually advised to stay in place because both firefighters and evacuating residents share a single stairwell, fire and building safety experts say.

Safety standards are meant to contain fires to the individual apartment affected, and keep stairwells and hallways free of smoke for some time, says Graham Fieldhouse, allowing the fire to be fought and evacuations carefully managed.

"[Firefighters] don't need hundreds of people coming down the stairs when they are trying to fight the fire," the fire safety expert told the ����ý.

But at Grenfell Tower, it's clear that things did not work as they should have.