![]() Selection of equipment for air-sampling is important and depends on many factors such as the purpose of sampling, type of sampling, type of equipment available, nature of toxicant, environmental conditions, required accuracy and sensitivity, reliability, the property of air-contaminant, presence of other chemicals which may mix or interfere, duration of sampling, cost, etc. Passive or diffusive’ air sampling involves the collection of airborne gases/vapors through a diffusion barrier onto an absorbing medium without the use of an air sampling pump and (2) Active air samplingĪctive air sampling involves the collection of airborne contaminants by means of a forced movement of air by a sampling pump and through an appropriate collection medium i.e. Types of sampling are also classified as (1) Passive or diffusive’ air sampling An air-sampling train consisting of the air-inlet orifice, collection media (solid or liquid sorbent, filters, and passive monitors), air-flow meter, flow-rate control valve, and suction pump, is used by qualified and trained personnel. gas detector tubes or digital meters) to measure STEL value for 15 minutes and TLV for 8 hr TWA limits. Integrated sampling is carried out by direct-reading instruments (e.g. It should not be used for reactive gases. Temperature and pressure should be recorded during sampling. Direct reading instruments can also be used for grab sampling. The sample is collected in an evacuated flask or plastic bag, sealed and sent to a laboratory where trace analysis is carried out by gas chromatography, IR spectrophotometry, etc. peak value of NH3 or Cl2 at a particular time. Grab sampling is used to measure concentration at a particular time (at least two samples within 5 minutes) e.g. Short period (instantaneous) sampling is called grab sampling and long-period sampling is called integrated sampling. It includes continuous monitors for leak detection, ventilation failure, equipment malfunction, etc. In area sampling, the air samples are taken at fixed places in a workroom or confined spaces to evaluate general concentrations of flammable, explosive, or toxic material in the air for the purpose of isolation or restriction to work or to design the control measures. In personal sampling, the sampling device is worn by the worker near his breathing zone to evaluate personal or individual exposure to him. Types Of Air Sampling 1.Personal Sampling To determine the types and effectiveness of the control measures provided, any change if necessary in them and new control measures to be provided.To determine type and concentration of exposure due to health hazards to workers.Osha’s some permissible exposure limits in parts per million (ppm).Types of sampling are also classified as.
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