Strange Illness strikes teachers/custodians in a Houston School!

There is still things that happen in the US that people of science cannot possibly explain.

In a Houston middle school – Francis Scott Key School, teachers are custodians have been falling sick.  So much that they have to be taken to the hospital.  Strangely, though parents say that kids have also been sick.. none of the kids as yet have been taken to hospital sick.  What is the illness like?

Since the first day of school on Aug. 27, more than 15 teachers and seven custodians have suffered from severe headaches, chest pains, breathing problems and vomiting while inside Francis Scott Key Middle School.

And the way it happens is even more strange:

The strange illness first surfaced in late August, when science teacher Ronald Jacobs began to cough and wheeze and had trouble breathing after spending time inside a classroom.

The symptoms went away when he left the room, but came back more violently when he returned. Staff called 911 when his throat tightened and his eyes swelled.

Any doctors amongst the readers?  What do you think is the reason?