The Occupational Safety and Health Administration (OSHA) requires that industries provide engineering and administrative controls to prevent particulate and vapour hazards in the workplace. These controls may include proper ventilation, limiting exposure to hazards, voluntary health assessments for employees and the implementation of a respiratory protection plan.
Air filtering respirators are either air line respirators, such as the self contained breathing apparatus respirators (SCBA) used by emergency first responders and other highly specialized fields, or air purifying respirators, commonly used in construction, welding and health care. Air purifying respirators can be re-usable and/or disposable and are used in environments that contain at least a 19.5% oxygen level. A filter or cartridge removes impurities and contaminants as ambient air flows through the respirator. In order for respirators to work efficiently, they must be properly fitted by either an employee trained in fit testing, or a trained independent consultant.
Qualitative Fit Testing (QLFT)
Qualitative fit testing (QLFT) of a respirator is a subjective test which allows a fit tester to fit up to six people at a time for a respirator. QLFT is a cost effective method that does not involve complex machinery and is a series of tests that take less than eight minutes to administer. The results of QLFT can be misinterpreted due to the subjective nature of the testing; test subjects with medical issues can also prevent effective QLFT.
QLFT involves the proper selection of a respirator, both in size and purpose. The seal of the respirator is checked for any leaks when the employee inhales and exhales. Then the employee, wearing the respirator, dons a hood and is subjected to a series of tests involving sensitivity to an external agent, misted into the hood.
QLFT Agent: Irritant Smoke
Irritant smoke, or stannic chloride, is sometimes used as an agent to determine whether a respirator has been properly fitted. An employee's involuntary reaction is gauged when fumes of irritant smoke are pumped through tubes, into the hood. If the employee gags or coughs, the respirator has not been properly fitted as there is an obvious interruption in the seal.
The National Institute for Occupational Safety and Health (NIOSH) has recommended, as of July 1999, the disuse of irritant smoke as a QLFT agent due to the hazard of overexposure to the hydrogen chloride solution, while OSHA continues to recognize irritant smoke as an acceptable QLFT agent.
QLFT Agent: Saccharine
Saccharine is a readily used QLFT agent due to the very low risk of allergic and adverse reactions in test subjects. A saccharine solution is misted into the hood while the employee, wearing the respirator, inhales and exhales through the mouth. If the employee can detect the "sweetness" of the saccharine, the respirator must be refitted. Because the saccharine is a super saturated solution, it tends it crystallize and clog the nebulizer used to mist the solution into the hood. Saccharine testing also tends to render varying degrees of success due to the fit tester's inability to read any discernible difference in the test subject's reaction to a relatively pleasant agent.
QLFT Agent: Bitrex
Bitrex, or denatonium benzoate, is a bitter solution commonly added to household cleaners to prevent children from inadvertently ingesting hazardous products. When Bitrex is used as a QLFT agent, the tester's reaction is very evident if the respirator is not properly fitted. Bitrex has not been found to produce any allergic reactions.
QLFT Agent: Isoamyl Acetate
Isoamyl acetate, commonly known as banana oil, is another agent used in detecting improperly fitted respirators. The distinct banana taste is easily detected by testers if they are donning an ill-fitting respirator. Isoamyl acetate is limited as a test agent to respirators that resist oil and are therefore not used as a test agent for N series respirators used in the health care sector.
QLFT Exercises
While the test subject is undergoing the fit testing with the misted agent, the subject must perform a series of exercises that take one minute each, including moving the head up and down and from side to side, bending, standing and sitting. One of the exercises also include the recitation of the Rainbow passage, a passage that has the reader pronouncing every vowel sound in the English language. If the test agent cannot be detected after these exercises, the respirator is deemed a passable fit for the wearer.
Quantitative Fit Testing (QNFT)
In quantitative fit testing (QNFT), the subject dons the respirator and performs the same exercises found in QLFT. Rather than using an external agent to detect leaks in the respirator's seal, the subject's personal protective equipment is attached to a calibrated machine that measures the internal air and compares this to the ambient air. QNFT involves more cost for the employer and is more time consuming because only one subject can be tested at a time. QNFT, however, produces an objective perspective and can result in a higher applied protection factor for the respirator.
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