Sorry this is off topic, I just wish people with no knowledge would keep their fingers off the keyboard.
How wrong can you be NAROBS. As someone who maintained a large building in London I can tell you how fire cover works.
Buildings are graded by the fire services, in my case the building was called a section 20. This required high temperature detectors in non-operational areas and a 24 hour cover by my staff. If a temperature alarm went off it had to be investigated and the fire services called if a fire was found.
This arrangement led to an embarrassing episode. One night in the early hours an alarm went off, two staff went to investigate. One was a rugby player the other one could handle himself. When they opened the door to the room with the alarm, they were jumped on and a fight took place. The end result was Building Maintenance 1 – 0 Met Police. The police had been given a heater to keep themselves warm, yes they had it under a temperature detector. The police were using the higher floors of the building a watch tower.
Personally I think the airport authorities acted correctly in closing the airport. If most units had been called out to two suspect fires, they had no option but to stop all aircraft movements.