Questions often arise as to how easy clothing becomes contaminated on the fireground and if there are differences in the level of contamination for the same items of a protective ensemble. The issue frequently comes up in distinguishing between rubber and leather footwear, but it is a reasonable inquiry for the overall clothing system. We have looked at contamination of different materials and can offer some insight to help firefighters determine if they need to be concerned about different exposure events. Contamination occurs when some unintended substance gets on or in clothing or equipment. It may be minor such as light soiling or intrinsically dangerous like a splash of a strong acid. Contamination implies substances that are unwanted because of their potential health effects. It is also important to recognize that contamination may be transient, either leaving the clothing on its own with time or through cleaning. The greatest concern is for contamination that is persistent and continues to expose the firefighter to the hazard.