In June, the NIOSH National Personal Protective Technology Laboratory (NPPTL) posted on its website instructions to make the OSHA-approved fit test and threshold check solutions for the Saccharin Solution Aerosol Protocol, Bitrex (Denatonium Benzoate) Solution Aerosol Qualitative Fit Test Protocol, and Isoamyl Acetate Protocol. These solutions are used in qualitative fit testing, which relies on respirator wearers’ sensory detection of these test agents.  “The agents used in qualitative fit testing are usually available commercially in convenient, ready-to-use packaging that contains premade dilutions of the reagents,” NPPTL says. “When these ready-to-use packages are not available, the [qualitative fit test] can be performed by using the required solutions prepared from commercially available reagents.” NIOSH states that qualitative fit testing is the preferred method during the COVID-19 pandemic because it can help slow the depletion of the inventory of N95 respirators. Respirators used for a qualitative fit test can be worn again after the test, whereas respirators used for a quantitative fit test must be disposed of afterward because the quantitative method requires a hole to be punched in the respirator.