Carpets Get Cleaner and Healthier – Measuring Carpet Cleaning Effectiveness with XRF

You may or may not have heard of X-ray Fluorescence (XRF): The technology was originally developed by NASA to test for metal impurities that could cause premature or even catastrophic wear of vital space shuttle components, such as those used in the space shuttle Discovery. The science was adapted by the Carpet and Rug Institute (CRI), and on September 12, 2005, was officially adopted as the basis of the institute’s Seal of Approval testing and certification programs for restorative carpet extractors designed for deep cleaning. Comparable approval programs for vacuums and other carpet care products are also being deployed, marking the first time NASA-enhanced technology has been transferred to an entire industry.

In simple terms, XRF, as used by NASA, works by shooting a beam of energy at an alloy and identifying its components based on the energy of the returned signals. The CRI model—developed in collaboration with NASA; Keymaster Technologies, Inc.; and Professional Testing Laboratory, Inc. (PTL)—operates similarly. Using a hand-held device, a beam of energy is shot into the carpeted surface. Return signals detect and identify soils left behind after cleaning.


Pre-XRF, some testers were forced to rely on a process that uses a spectrophotometer to measure the light values reflected from carpet pile to indicate cleanliness. While certainly better than nothing, this method fails to quantify the actual soil removed. Similarly, since 2000, CRI certified vacuums for soil removal under its Green Label program, using a weight-based method: Carpet was soiled, weighed, vacuumed, and weighed again to detect variances as slight as one hundredth of a gram. Yet here, too, the identities of the residual soils remained a mystery—as did the best products for removing them.


In contrast, XRF identifies the individual components of a near infinite range of soils—down to an unprecedented four decimal points. It also provides insight into how these components are affected by various cleaning methods and other conditions.