U of I air filter inventors finding new uses for it, from purifying the air astronauts breathe to eliminating the smell of cat urine Jul 6, 2017 1:15 pm by Crain's Chicago BusinessIllinois in the News Share on Facebook Tweet Email Images Their air filters' patented absorptive coating removes toxic chemicals, odors from the air - and it changes from magenta to yellow when it needs to be replaced Share on Facebook Tweet Email