I’m so happy to be part of and actively participate in the IICRC Standards of Care for this industry. I can’t rely on waiting for the old standards and the new standards to go public, there are so many redefined and defined (new) words. They even clarified language for us. But here are some definitions that have been in our industry. I can’t wait to see how they are cleaned up and/or presenting new definitions.
Knockdown (verb): (syn.) pulldown: 1. An act of using aerosolized fine liquid droplets to reduce airborne solid particles by the act of attaching or absorbing the solids to the liquid until heavy (massive) enough to fall to the surface due to gravity. 2. a method of dust control (suppression and/or capture). Fog and mist are put into the air by special equipment with the intent to remain airborne for a predictable amount of time long enough to attach to or absorb solid particulates and, when heavy enough, will fall to the ground, i.e., knock or pull them down to the surface below.
The droplets and particulates that fall to surfaces due to knockdown are considered knockdown residue, or simply, residue. Physical cleaning of the knockdown residue is required to return a surface to Condition 1. See also the definition of “dust control”.
Dust Control: suppression and/or capture and/or removal of small solid particles from surfaces or air, usually with mechanical methods such as vacuum, filtration, cloth, liquid, or with a barrier or covering that prevents escape via large openings or pores (e.g., plastic sheet, spray encapsulant). The selection of the particular method depends on the size and concentration of controlled dust particles. For this standard (i.e. S520 Standards for Mold Remediation), it is stipulated that dust at or near Condition 3 growth or in a defined remediation workspace (i.e., by the containment and critical barriers) contains Condition 2 contamination. Thus, as a corollary, it can be assumed that adequate and/or complete removal of surface dust will also remove some, most, or even all of the Condition 2 contamination from that surface. See also definitions of Condition 2 and contamination.
Fog (noun): airborne liquid droplets typically defined as smaller than 50 microns. Fog droplets are smaller than mist droplets. Both will remain suspended in the air (airborne) for a predictable amount of time. Fog droplets remain airborne for a longer duration than mist droplets. Fog droplets are more likely to drift. Surfaces wetted by fog droplets may dry by evaporation more quickly, reducing the time available to wipe and remove the wet residue prior to re-aerosolization of the particulates as well as reducing the probability that a required contact (wet dwell) time will be achieved. A fog does not wet surfaces as well as mist or spray applications (although increased volume of droplets applied can compensate). Application velocity can also affect wetting.
Fogging/Misting (verb): act of putting fog or mist in the air. For the purposes of this standard, fogging and misting are dust control methods that suppress and capture solid particulates, both in the air and on surfaces.
Fogging and misting use special equipment to generate relatively uniform-sized liquid droplets that are dispersed into the air. In general, selection of fog or mist is based on the size of the particles intended to be captured or absorbed. The general rule is like-sized captures like-size. The smaller fog droplets are appropriate for control of particulates smaller than 50 microns, such as mold spores and fragments and other particulates that are often smaller than 20 microns. The larger mist droplets are appropriate for control of particulates larger than 50 microns such as dust likely to be generated from construction activities such as sawing or demolition.
All three types of droplets (fog, mist, spray) can also be used to apply liquid directly to unclean surfaces for dust control of loose settled particulates and can be used to apply liquid-based cleaning products to unclean surfaces or liquid-based disinfecting products following physical removal of mold (i.e., no visible, dirt, dust, debris, and visible mold). Fogging, misting, and spraying apply liquids to the surface at different rates and volumes. For the purpose of this standard, spraying is not used as an airborne dust control method.