Do not operate your iMac in areas with significant amounts of airborne dust, or smoke from cigarettes, cigars, ashtrays, stoves, or fireplaces, or near an ultrasonic humidifier using unfiltered tap water. Tiny airborne particles produced by smoking, cooking, burning, or using an ultrasonic humidifier with unfiltered water may, in rare instances, enter the ventilation openings of your iMac and, under certain conditions, result in a slight haze on the inside surface of the glass panel that covers the iMac display.