The Qualitative Fit Test (QLFT) is a pass/fail procedure designed to ensure a tight-fitting respirator forms an adequate seal against the wearer’s face, a fundamental requirement for respiratory protection. This process is necessary because respirator sizes and facial features vary widely, meaning a single model may not fit every individual securely. The test relies on the wearer’s sense of taste to detect a harmless aerosolized chemical introduced into a hood placed over their head and the respirator. Two primary agents are commonly used: saccharin, which produces a sweet taste, and Denatonium Benzoate (Bitrex), which creates an intensely bitter sensation.
Interpreting the Taste Sensation
Detecting the sweet taste of saccharin or the bitter taste of Bitrex at any point during the fit test immediately signifies a test failure. This taste confirms that the aerosolized test agent has penetrated the respirator and reached the inside of the facepiece. This penetration indicates a breach in the facial seal, which would allow contaminated air to enter the mask in a hazardous environment. A detected taste confirms the respirator is non-functional for its intended protective use, placing the wearer at risk of exposure to airborne hazards.
Common Factors Causing Seal Breach
A fit test failure is almost always due to a compromised seal caused by specific, identifiable factors. The most common reason for a seal breach is the presence of facial hair, including stubble, which prevents the facepiece material from making direct contact with the skin. Even a day’s growth of stubble can create channels for air leakage, making it mandatory for wearers of tight-fitting respirators to be clean-shaven in the seal area.
Improper donning is a frequent mechanical cause of failure, often involving incorrect strap tension that is either too loose or too tight. A facepiece that is the wrong size for the wearer’s facial dimensions will also fail, as gaps may be present around the nose, chin, or cheeks despite correct donning. Because respirators are not standardized in size across models, multiple makes and sizes must be available to ensure a secure fit.
Other factors can interfere with the seal, such as significant changes in body weight, dental changes, or facial scarring that alter the face’s shape. Eyewear, like glasses or goggles, must be worn during the fit test if they are used in the workplace, as the frames can break the seal around the temples. Additionally, movement during the procedure, such as talking or coughing, can temporarily distort the facial seal and cause a momentary leak.
Necessary Steps Following a Failed Test
When the sweet or bitter taste is detected, the test subject must immediately signal the administrator to stop the procedure. The failed test result must be documented, and the current facepiece is deemed unsuitable for the wearer. Remediation begins by having the wearer re-don the same respirator, paying close attention to strap adjustment and nosepiece placement.
If the failure persists after re-donning and adjustment, the next step is to try a different size or a completely different make and model of respirator. The individual must be re-tested on each new respirator until a successful fit is achieved. Regulatory requirements mandate that a record of the fit test, including the exact make, model, and size of the passed respirator, be maintained.