Complex sentence: On 24 June 2009, one of the school's coal-fired central heating boilers exploded while maintenance on the heating system was being carried out, blowing the roof off the boiler house and shattering windows across the school.
Split into simpler sentences: On 24 June 2009, one of the school's coal-fired central heating boilers exploded while maintenance on the heating system was being carried out. The explosion blew the roof off the boiler house and shattered windows across the school.