CM/Spotlight: Infection control Part one in a series of exclusive research papers. Published with permission by the Cleaning Industry Research Institute © 2008. By: Michael A. Berry, Ph.D. T This is part one of a four-part series on the “Science-based steps of the cleaning process.” Each step contains scientific concepts and prin-ciples explaining cleaning’s effectiveness in put-ting unwanted matter in its proper place. Specifying and understanding the nature and charac-teristics of the environment or sub-compartment to be cleaned. How is matter measured and transferred? Particle counts measure matter in an environ-ment’s compartment. Generally, this is irrelevant since our interest is the mass of substance, not the number of micro-scopic particles. Consequently, virtually all environmental health information relates to substance mass not particle count. How is matter transferred? Large, dense substances, such as clay, sand, oils, grass, leaves and some biomass, usually are tracked inside at ground level. Irregular or porous surfaces tend to collect and hold fast to foreign matter. Carpet has a large, irregular surface area and strong holding characteristics. Temporary containment — also known as the trap effect — helps carpet control indoor pollutants. Carpet dusts commonly are 85 to 95 percent dry soil and are tracked in from outside. Typically, these dusts are greater than 20 µm. These larger, denser particles are trapped by carpet close to entrances. Because of their size and density, once they inhabit the carpet it is unlikely they will return to air. Matter transfers from air to surfaces through gradual settling, impaction, filtration and elec-tronic attraction. Generally, large dense particles transfer faster than less dense matter. Matter transferring from surfaces to air prima-rily is a function of attractive forces between the matter and its surface. What is unwanted matter? Michael D. Berry, Ph.D., was chairman of the Science Advisory Council for the Cleaning Industry Research Institute (CIRI) in 2006. The information contained in this article was extracted from Dr. Berry’s papers and presentations at CIRI’s 2007 Cleaning Science Conference and Symposium. His entire paper and PowerPoint presentation, as well as those of other symposium presenters, are available at www.ciri-research.org. for more info Visit www.cmmonline.com and type in search keyword: CIRI . For more information on related products, visit www.cmmonline.com , select SUPPLIER SEARCH from the main navigation bar, and enter keywords: Consultant services . Unwanted matter is brought indoors by foot traffic, air deposits, impact, filtration or other out-door sources. Basic physics suggests all matter transfers in and out of compartments, such as carpet, hard floors, fabrics and, to some degree, HVAC. It is carried between compartments by physical displacement, gravitational settling, air current impact or filtration, electro-attraction or direct contact, like tracking. Substances circulating indoors have differ-ent shapes, sizes, chemical compositions, den-sities, absorption, adsorption and adhesion characteristics. Dusts are the heterogeneous mixture of these solid particles. Substances are measured as a micron or micrometer unit. A micrometer (µm) = 1/1,000,000 of a meter. A micron or micrometer-size particle is about 100 times smaller than a grain of salt. Particles between 30 and 40 microns are nearly invisible. Their mass is calculated in grams. Substances measured as air concentrations are calculated as micrograms (millionth of a gram) per cubic meter of air (µg/m 3 ). 22 CM/Cleaning & Maintenance Management ® • February 2009
CMM – Archives Feb 2009: 22
