What is the difference between qualitative (QLFT) and quantitative (QNFT) fit tests?
What is the difference between qualitative (QLFT) and quantitative (QNFT) fit tests? When do each of them need to be used?
Respirators are designed to protect the user from exposure to various inhalation hazards, including vapors, fumes, and particulate matter. But a respirator can only perform this function if it fits tightly against the wearer's face and creates a protective seal.
Anytime a respirator is put on, the user should do a quick check of the seal to make sure that the device is securely in place. But this simple check is not enough to ensure the user's full protection. The respirator must also be put through a fit test at least once a year and whenever the user undergoes a significant facial change (due to weight gain or surgery, for instance).
But here's where some people get confused. There are two kinds of fit testing – qualitative and quantitative – and it's not always clear which one should be performed.
Qualitative Fit Testing (QLFT)
Let's start with the qualitative fit test. This one relies on the wearer's sense of taste and smell to detect whether the respirator provides a tight seal.
To perform this test, the mask is donned and one of four substances is released (isoamyl acetate, saccharine, bitrex, or irritant smoke). If the user can smell, taste, or is otherwise affected by the substance, it means the seal does not provide adequate protection.
The qualitative fit test is normally used for half-mask respirators. If you're testing a full-face respirator, the quantitative fit test is recommended instead.
Quantitative Fit Testing (QNTF)
Unlike the qualitative test, the quantitative test relies on a machine that attaches to the respirator via a tube to measure any leakage.
The quantitative test not only detects the presence of a leak, but also measures the amount of leakage.
Quantitative fit testing is normally the preferred option for full-face respirators, although it can still be used for half-mask models.