QLFT Fit Test Method
The Quantitative Fit Test (QNFT) is an objective test that uses an instrument to check the fit of a respirator. The measurement does not rely on the subjective response of an individual. The instrument measures the concentration of the test aerosol outside the respirator (Cout) and then measures the concentration of the aerosol inside the respirator (Cin). The ratio of the two measurements (Cout/Cin) is known as the fit factor OSHA requires that half mask respirators such as the N95 filter mask have a fit factor of at least 100 to pass the fit test. Do not confuse a passing fit factor of 100 with the OSHA Class 10 specified protection factor for N95 respirators in the workplace. The fit test utilizes one safety factor. Quantitative and Quantitative Fit Testing There are two OSHA-accepted QNFT methods that can be used to fit test N95 filtering facepiece respirators.
? Generated Aerosol Method
The Generative Aerosol Method. Ambient Aerosol Method
Generated aerosol fit testing systems are considered the "gold standard" but are complex and not portable. These systems are generally found only in the research and product development laboratories of respirator manufacturers. The other type of environmental aerosol method is commercially available and very portable. Because of their many advantages, they are becoming more common in medical settings.

The ambient aerosol QNFT instrument measures the concentration of aerosols inside and outside the respirator and calculates a fit factor. The test aerosols we use are very small particles in the environment that are present in the air we breathe all the time. These particles cannot penetrate the respirator's filter media, so any particles measured inside the respirator are due to a leaky face seal. More than 20 years ago, TSI, Inc. of Shawville, Minnesota, first introduced the Ambient Aerosol Suitability Checker. Over the years, TSI has updated the instrument in several iterations. The latest model to perform N95 respirator fit testing is the PORTACOUNT®PRO+ Model 8038. The QNFT method is objective and eliminates the influence of individual sensitivities and subjective attitudes of respirator-wearing subjects. The instrument checks the fit and automatically records the results when the subject performs a series of specific maneuvers. the advantage of the QNFT method is that they are well suited for automated testing, record keeping and management by computer and software, as well as the printing of a fit card that is easily carried by the employee. The software ensures that the fitness testing protocol is followed precisely, making it virtually impossible to make errors. It also eliminates the tendency of test operators to shortcut the process, which can affect the effectiveness of qualitative methods. The QNFT system uses computers and software to simplify the suitability testing process as much as possible. The test operator cannot skip important test steps because the test process is programmed. Nor can the test subject cheat the QNFT instrument. Record keeping and report generation are made easy, and the instrument automatically creates a respirator fit test card that can be kept by the healthcare provider. This card helps people remember which model and size respirator they can use and, if necessary, proves that they have a current fit test. The TSI PortaCount Pro+ Fit Tester eliminates the guesswork, tedious and error-prone steps of traditional qualitative fit testing methods. When a respiratory protective mask needs to be tested for fit, it provides a quick and easy fit test that is fully compliant with OSHA standards and GB19083-2010 Technical Requirements for Medical Protective Masks, and is the only quantitative fit tester that can be used with all types of respirators, including N95 masks.