WLS14901071 / 14901071 THRESHOLD SCREENING SOLUTION BITREX Willson® Bitrex™ Fit Test Kit Bitrex™ Fit Test Kit takes the guesswork out of qualitative fit testing and reduces fit test errors. Simple, reliable, and safe, Bitrex™ (Denatonium Benzoate) is a bitter solution that creates an involuntary response by your employees. Includes fit test solutions, two nebulizers, Tyvek® test enclosure and instructions. Made in USA. Meets OSHA requirements as qualitative fit test for both disposable and reusable respirators. Ampules sold 18 tests per case.