London tubes can get overheated during the summer months.
News that air conditioning will soon be a feature on London's tube network is sure to be music to the ears of the millions of commuters who use it each day.
Heat control has been an ongoing problem, especially in the summer months when passengers have to endure scorching temperatures.
In July 2001 three packed Victoria Line trains were stopped in a tunnel outside Highbury and Islington station, in north London, for 90 minutes in sweltering conditions.
About 600 people had to be treated for heat problems with 18 so badly affected they had to be taken to hospital.
The first section of the tube to open was between Farringdon and Paddington in 1863
There are 250 underground stations in London
3.5 million people use the tube daily
Jason Groves, who was travelling on that day, said: "It was just getting hotter and hotter and hotter. People were starting to rip the advertising boards off above the seats, and try to use them as fans, but you were packed so tight, you couldn't really do that.
"There was a pregnant woman collapsed... everyone was crying out for water but you don't take much water in with you if you're just going to work."
Failed attempts to cool the heated tubes prompted the then London Mayor, Ken Livingstone, to launch a competition to find a solution to the problem.
In 2003 he announced a prize of £100,000 to the person who could find a solution to London's overheated underground.
More than 3,000 entries were received but not one was considered workable and the initiative was abandoned.
The new trains scheduled to be unveiled in September 2010 will be longer and larger than current trains and will increase capacity by nearly 20 per cent.
The air conditioned trains will be introduced on the Metropolitan line, followed by the Circle, Hammersmith & City and District Lines.
London Underground is also trying to develop ways to install air conditioning within the network's deep lines, such as the Northern and Victoria line.
The new trains will have a back-up if the air conditioning system fails or if a train gets stuck in a tunnel for a prolonged period of time. It can be maintained for up to two hours.
Transport for London took control of the Tube in July 2003 and attempts to try to cool the network were not backed by investment, it has claimed.
A spokesman said: "Setting up a dedicated 'cool the tube' team was part TfL's commitment to co-ordinate a programme to understand the problem and to invest to try to tackle heat on the Underground in future."