CAL OSHA BREATHING ZONE FULL
A minimum fit factor pass level of 100 is necessary for a half-mask respirator and a minimum fit factor of at least 500 is required for a full facepiece respirator. Instantaneous feedback in the form of a real-time pressure trace of the in-mask pressure is provided and used to determine test validity and quality. The quality and validity of the CNP fit tests are determined by the degree to which the in-mask pressure tracks the test pressure during the system measurement time of approximately five seconds. The facepiece fit is expressed as the leak rate through the facepiece, expressed as milliliters per minute. To perform the test, the test subject closes his or her mouth and holds his/her breath, after which an air pump removes air from the respirator facepiece at a pre-selected constant pressure. The CNP instrument manufacturer Occupational Health Dynamics of Birmingham, Alabama also provides attachments (sampling manifolds) that replace the filter cartridges to permit fit testing in an employee's own respirator. The CNP fit test method measures leak rates through the facepiece as a method for determining the facepiece fit for negative pressure respirators. Therefore, measurement of the exhaust stream that is required to hold the pressure in the temporarily sealed respirator constant yields a direct measure of leakage air flow into the respirator. With pressure held constant, air flow out of the respirator is equal to air flow into the respirator. The level of pressure is selected to replicate the mean inspiratory pressure that causes leakage into the respirator under normal use conditions. The rate of air exhaust is controlled so that a constant negative pressure is maintained in the respirator during the fit test.
The CNP fit test method technology is based on exhausting air from a temporarily sealed respirator facepiece to generate and then maintain a constant negative pressure inside the facepiece. The CNP protocol provides an alternative to aerosol fit test methods. Controlled negative pressure (CNP) quantitative fit testing protocol.
The entire screening and testing procedure shall be explained to the test subject prior to the conduct of the screening test.Ĥ. A minimum fit factor pass level of at least 100 is necessary for a half-mask respirator and a minimum fit factor pass level of at least 500 is required for a full facepiece negative pressure respirator. The CNC instrument manufacturer, TSI Inc., also provides probe attachments (TSI sampling adapters) that permit fit testing in an employee's own respirator. A probed respirator is required for each make, style, model, and size that the employer uses and can be obtained from the respirator manufacturer or distributor. A probed respirator has a special sampling device, installed on the respirator, that allows the probe to sample the air from inside the mask.
The probed respirator is only used for quantitative fit tests. The ambient aerosol condensation nuclei counter (CNC) quantitative fit testing (Portacount TM) protocol quantitatively fit tests respirators with the use of a probe. Ambient aerosol condensation nuclei counter (CNC) quantitative fit testing protocol.
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