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AWS F1.1M:2018 pdf free download
AWS F1.1M:2018 pdf free download.Methods for Sampling Fumes and Gases Generated bu Welding and Allied Processes.
14. Carbon Monoxide (5 ppm to 500 ppm)
14.1 Sampling. There are many acceptable methods for sampling and analysis of carbon monoxide. Certified ga standards are readily available for calibration.
14.2 Instrumcnt.s. Both passive and active sampling devices for carbon monoxide are available. The following are commonly used instruments:
14.2.1 Electnwhcrnlcal Cell Devices. An electrochemical cell device converts carbon monoxide passing over the sensing electrode to carbon dioxide. The current caused by the electrochemical oxidation is amplified and displayed on the readout. Instruments are available w determine “snapshot” measurements or average concentrations.
14.2.2 Solid-State Devices. These instruments make use of a metallic oxide semiconductor (MOS) sensor, sometimes referred to us a solid-state wnsoi Oxidation of carbon monoxide as it passes the sensor results in changes in the conductivity of the sensor. These instruments are usually used to obtain instantaneous readings.
14.3 I)ctcctor Tuhcs and Passive Samplers. Detector tubes are available for measurement of carbon monoxide that provide a “snapshot” measurement and require an aspirating pump.
Long-term detector tubes provide an average concentration over an 8-hour period. Depending on the manufacturer, a mechanical aspirating pump may be required to bring the sample to the reactive site. The reading. depending on the type. will be length of stain or color intensity. The length-of-stain passive monitors can be used to provide an average concentration over periods up to 8 hours.
Color intensity monitors establish whether a total CO exposure of 4(X) ppm-hours or an average concentration of 50 ppm [OSHA Permissible Exposure Limit (PEL)1 over an eight-hour period has been reached.
14.4 Chemical Methods. There arc no suitable chemical methods for analysis of carbon monoxide, A reference to an OSHA analytical method is provided in Annex C.
14.5 Calibration. Detector tubes and instruments may be calibrated using a calibration (span) gas with a certified or known concentration of carbon monoxide. Care should be taken to ensure that adequate moisture is present in the air- stream, since insufficient moisture will affect the calibration of’ the instrument. The manufacturer’s Instructions regarding humidification of the span gas shall be consulted.
14.6 Recommended Method. All methods mentioned are equally suitable.AWS F1.1M:2018 pdf free download.
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