Use of Conductivity as a Tool for On-site Residue Management and Definition of Smart Cleanroom Regimes

Surface residues that result from the use of cleaning and disinfection products are becoming an increasing focus of regulators in the Cleanroom industry. Driven largely by the update to EU GMP Annex 1 [1] and best practice recommendation from the PDA Journal of Pharmaceutical Science and Technology [2], it is now recognized that residues need to be managed to avoid any risks they could present to safety or product quality. Residue management can be successfully achieved by selection and use of low residue disinfectants, through the frequency and choice of rinsing agent for removal, the use of the most suitable tools for physical removal like cleanroom specific mops, or a combination of all these factors. Unlike product contact surfaces [3], there is no clear guidance as to what level of residue may be acceptable on small or large cleanroom surfaces, or how they can be quantified. For this reason, most people still rely on judging a surface to be ‘visibly clean’. To improve detection and to quantify the level of residue on a cleanroom surface, a pragmatic method has been developed to measure residue anywhere on-site: Quantification of disinfectant residues by the use of conductivity. The method of quantification of disinfectant residues using conductivity has been verified in studies by measuring the residues derived from different disinfectant types, at various scales (from bench scale upwards) and various locations, and from laboratory to representative pharmaceutical manufacturing areas. Compared to the current ‘gold standard’ that has long been used for the assessment of residues – an individual’s judgment of ‘visually clean’ - the data from conductivity measurements can eliminate this subjective human appraisal and replace it with scientific assessment. Comparison of the visual analysis rating versus conductivity data also revealed that the human eye does indeed underestimate the actual levels of disinfectant residues remaining on surfaces in a cleanroom, resulting in potential impacts of risk to safety, contamination, time, and cost.