Technical Guide 1003 covers the realm of macroparticles, the particles of concern with respect to operations involving the "other end" of the controlled environment spectrum. Particles of this size range are most commonly of interest for classification and monitoring in cleanrooms and clean zones having air cleanliness classifications that would generally qualify as ISO Class 5 or less clean. The air cleanliness is expressed in terms of the M descriptor, the numerical value of the concentration of macroparticles per cubic meter. This Guide contains descriptions of apparatus and procedures for classification (in accordance with ISO 14644-1) and monitoring (in accordance with ISO 14644-2) of clean environments requiring control of airborne contaminants in the macroparticle size range.