Thirteen students and a teacher at Joshua Cowell School were overcome by chemical fumes Wednesday afternoon including five that were transported by ambulance to Doctors Hospital of Manteca. They were exposed to a sealant chemical that entered their classroom through a heating ceiling duct at about 2 p.m. The six students transported to Doctors Hospital were treated for respiratory systems issues after inhaling the chemical that caused a degree of light headedness as well as anxiety. A call to the Poison Control Center calmed fears when a medical doctor told a staff member that the children would have to have a more concentrated exposure to the chemical to suffer serious affects.