*MSA Bitrex Qualitative Fit Test Kit
For Chemical Respirators*
20 December 2010
This is a how to guide for the fitting and testing of gas masks in particular, but can be used for any type of chemical filtering respirators using the MSA brand Bitrex kit.
The Bitrex (Denatonium benzoate) solution aerosol QLFT protocol uses the published saccharin test protocol because that protocol is widely accepted. The American Medical Association, the National Safety Council, and the American Association of Poison Control Centers routinely use Bitrex as a taste aversion agent in household liquids. The entire screening and testing procedure shall be explained to the test subject prior to the conduct of the screening test.
Taste Threshold Screening. The Bitrex taste threshold screening, performed without wearing a respirator, is intended to determine whether the individual being tested can detect the taste of Bitrex. During threshold screening as well as during fit testing, subjects shall wear an enclosure about the head and shoulders that is approximately 12 inches in diameter by 14 inches tall. The front portion of the enclosure shall be clear from the respirator and allow free movement of the head when a respirator is worn. An enclosure substantially similar to the 3Mhood assembly. The test enclosure shall have a 3/4 inch (l .9cm) hole in front of the test subject's nose and mouth area to accommodate the nebulizer nozzle. The test subject shall don the test enclosure. Throughout the threshold-screening test, the test subject shall breathe through his or her slightly open mouth with tongue extended.
The subject is instructed to report when he/she detects a bitter taste. Using an Inhalation Medication Nebulizer or equivalent, the test conductor shall spray the Threshold Check Solution into the enclosure. This Nebulizer shall be clearly marked to distinguish it from the fit test solution nebulizer. The Threshold Check Solution is prepared by adding 13.5 milligrams of Bitrex to 100 ml of 5% salt (NaCl) solution in distilled water.
The Nebulizer Bulb
To produce the aerosol, the nebulizer bulb is firmly squeezed so that the bulb collapses completely and is then released and allowed to fully expand.
An initial ten squeezes are repeated rapidly and then the test subject is asked whether the Bitrex can be tasted. If the test subject reports tasting the bitter taste during the ten squeezes, the screening test is completed. The taste threshold is noted as ten regardless of the number of squeezes actually completed. If the first response is negative, ten more squeezes are repeated rapidly and the test subject is again asked whether the Bitrex is tasted. If the test subject reports tasting the bitter taste during the second ten squeezes, the screening test is completed. The taste threshold is noted as twenty regardless of the number of squeezes actually completed. If the second response is negative, ten more squeezes are repeated rapidly and the test subject is again asked whether the Bitrex is tasted. If the test subject reports tasting the bitter taste during the third set of ten squeezes, the screening test is completed. The taste threshold is noted as thirty regardless of the number of squeezes actually completed. The test conductor will take note of the number of squeezes required to solicit a taste response. If the Bitrex is not tasted after 30 squeezes, the test subject is unable to taste Bitrex and may not perform the Bitrex fit test.
Fit Test Subject With An Israeli Style Gas Mask
Now on to the fit test, which is similar in procedure to the sensitivity test, repeat Bitrex test using the Fit Test Solution in the appropriate nebulizer with the subject now wearing the chemical respirator or gas mask.
Research has shown that a taste based fit test is much more reliable than the smell tests using banana oil, smoke irritants or other similar chemicals. The taste buds are much more sensitive to the bitter taste than the receptors in the nose are to the other inhalation tests.
The solutions for the kit can be reordered from MSA North America http://www.msanorthamerica.com/catalog/product786.html
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