Which instrument is commonly used for quantitative respirator fit testing?

• A. PortaCount
• B. Nebulizer
• C. Thermometer
• D. Gas chromatograph

Answer: (A)

Quantitative respirator fit testing relies on measuring how well a respirator seals to the face by comparing particle concentrations outside and inside the facepiece during a test. The instrument used for this is a fit tester that counts ambient particles that leak through the seal and computes a fit factor. PortaCount is the standard device for this purpose because it uses a particle counter to continuously measure particle concentrations outside and inside the respirator while the wearer performs a series of movements and tasks, giving a numerical fit factor that indicates whether the fit meets required standards. This real-time quantitative feedback is what makes it suitable for compliance testing and for evaluating fit across different users and respirator models.

In contrast, a nebulizer is for delivering inhaled medications and may generate aerosols, but it does not measure how well a respirator fits. A thermometer is used for measuring temperature, not relevant to fit. A gas chromatograph analyzes chemical composition of samples, again not about respirator fit. PortaCount directly addresses seal integrity with objective data, which is why it's the chosen instrument for quantitative fit testing.