RESUMO
In this study, a modified procedure for quantitative fit testing of disposable masks and respirators using condensation nuclei counting was developed and applied. The procedure permits disposable masks and respirators to be initially tested and retested multiple times after use. Different types of masks and respirators were tested over time and quantitative results were obtained. It was found that after multiple testing that the N95 respirator passed the testing requirements with a fit factor above 100, the KN95 respirator did not perform satisfactorily in the tests, and the disposable masks did not reach fit factors above 4 or 7. The results in this study provided relevant information toward use, reuse, and testing of disposable masks and respirators, particularly relevant during the COVID pandemic when access to N95 respirators was limited.