The Illinois Poison Center says calls about carbon monoxide exposure spike 43 percent during colder months, and is reminding people that installing an alarm to detect leaks of the potentially deadly, odorless and colorless gas is state law. 

One Monday morning last fall, some students and teachers at North Mac Middle School in Girard weren’t feeling well. The health teacher, Alan Love, who also happens to be a registered nurse, told superintendent Marica Cullen the school might have a gas leak.