Thee school was placed under lockdown until police had searched the building and determined there was no further threat to students, said Patti Holm GREn, spokes woman for the school system.

In case of meeting the dust collecting efficiency of the system, the economical ventilation quantity was determined making the system to be operated under economic condition.

Relevance is not universal, but depends on the universe of meaning and the belief system under which relevance is determined.