Two new advanced security systems designed to spot potential terrorists have gone on trial at Britain's busiest airport.
Troops were deployed at Heathrow
One piece of new equipment quickly analyses vapours and particles from passengers' clothing to check whether there is any trace of explosives.
And an X-ray machine which gives a three-dimensional view of hand luggage could greatly increase the chances of spotting concealed weapons.
The trials began at London's Heathrow on Monday and, if they are a success, the British Airports Authority (BAA) expects to introduce them at airports across the UK.
The vapour testing machine uses jets of air to blow trapped particles from passengers' clothing as they walk through an archway.
Any residue is drawn into the machine and analysed for substances within seconds.
While the machine is not foolproof, it can test for dozens of types of explosives and sounds an alarm if even a tiny amount is found.
Bill Mawer, managing director of manufacturers Smiths Detection, said: "It's capable of detecting really, really very minute quantities, the kind of thing that would be left on a person's clothing."
The new technologies add yet further deterrent to anyone approaching the world's busiest international airport with sinister intent
Ian Hutcheson, BAA security director
Ordinary passengers will have to stand in the archway for a few moments, before an all-clear signal is given to the operator and they are able to move on.
Mr Mawer told BBC News Online the machine could also be used against drug smugglers, although that is not part of the Heathrow trial.
"It can detect drugs - there's no difference in the machine or the way it is set up," he said.
Security staff operating the new X-ray machine will have to wear special glasses to see the hand luggage in three dimensions.
Passengers will be selected at random to pass through both machines.
BAA's director of security, Ian Hutcheson, said: "I have high hopes for both these systems and, subject to trials here, I look forward to their wider
introduction across our airports."
He said plans to introduce the equipment were drawn up before security measures were heightened in recent weeks - including the deployment of the Army.
Mr Hutcheson said: "The new technologies add yet further deterrent to anyone approaching the world's busiest international airport with sinister intent."
He said both systems will be on trial for the foreseeable future at Terminal 1, which handles about 23m passengers a year.
Mr Hutcheson said BAA was spending about £165m a year on security at its seven UK airports.