Quantitative Fit Test (QNFT)

Last Updated: July 15, 2018

Definition - What does Quantitative Fit Test (QNFT) mean?

A quantitative fit test (QNFT) is one type of mask fit test used to determine whether a respirator properly fits an individual employee. Mask fits tests are used with tight fitting respirators to ensure that equipment fits the wearer properly. Without a proper fit, ambient air can leak into the mask and expose the wearer to airborne contaminants.

A quantitative fit test (QNFT) is performed by collecting and analyzing air samples from within the respiratory inlet cover of the respirator while it is worn by the intended user. This collection is accomplished through use of a hose inserted into the face piece of the mask, which then delivers the air sample to a separate device for analysis. This testing procedure results in a numeric value for the level of contaminants within the mask.By comparing this number to the concentration of the contaminant outside the mask, a fit factor can be calculated. This number should indicated if and at what level any leakage exists when the worker is wearing the mask.

A quantitative fit test differs from a qualitative fit test because the latter relies on subjective feedback from the wearer to detect potential leaks.

WorkplaceTesting explains Quantitative Fit Test (QNFT)

Because different mask styles and types fit differently, it is up to the worker and his or her employer to ensure that the right respirator is selected. A quantitative fit test (QNFT) is one way to ensure a respirator will operate correctly for an employee. A tight-fitting respirator's mask or respiratory inlet covering should fit securely against the face of the wearer forming a leak-proof seal that prevents airborne contaminants from being inhaled by the worker.

U.S. Occupational Health and Safety (OSHA) regulations require that a mask fit test be performed when a worker initially selects and is fitted for a tight-fitting respirator. Additional testing must be performed at least annually. A worker should be tested while wearing any other safety or personal equipment (such as glasses or hearing aids) that he or she will wear while working. Further testing may be required if an employee's facial features or structure change significantly. For example, if he or she begins wearing glasses, experiences significant weight gain or loss, or has major dental work.

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