Shawnee Mission Northwest High School in Shawnee, Kan., is replacing floor tile that is believed to have sickened 22 teachers and staff in science labs. Workers were removing tile last month and noticed an odor similar to tire rubber. Maintenance crews decided to put sealant over the pulled-up tiles and planned to put off the renovation until summer. But after teachers started getting sick and experiencing headaches, fatigue, difficulty breathing, sore throats, itchy eyes and runny noses, the district decided to replace the 15,000 square feet of floor covering immediately. Air-quality tests showed the presence of trace concentrations of chemical compounds at levels “many hundreds of times” less than the permissible exposure limits.