Air sampling procedures

A high volume Staplex air sampler with a vacuum capacity of 24 L/mln was placed horizontally on top of the berm facing towards the bed and operated for 2 hr. The air sampling procedure Including the preparation of the resin and extracting the captured pesticide vapors has been reported by Wehner et al. (3). 

This is particularly important in the case of an air sampling procedure, since the proper sampling of a gas is a difficult procedure with a wide range of possible errors. When planning and carrying out the sampling procedure, it is necessary to adhere particularly to the following principles ... 

The basic condition for a correct sampling is its isokinetic character. This means that during the analysed air sampling procedure, the gas flow rate through the opening of the sampling apparatus (inlet tubing) should... 

Hunt, G., Pangaro, N. Potential Contamination from the Use of Synthetic Adsorbents in Air Sampling Procedures, Anal. Chem. 54, 369 (1982)... 

The minimum air sample (litres) that will provide enough of the substance for the most accurate analysis at the TLV concentrations using the analytical procedures listed. 

A bulk sample is the last choice and the least desirable. It should be submitted "for laboratory use only" if there is a possibility of contamination by other matter. The type of bulk sample submitted to the laboratory should be cross-referenced to the appropriate air samples. A reported bulk sample analysis for quartz (or cristobalite) will be semi-quantitative in nature because (1) The XRD analysis procedure requires a thin layer deposition for an accurate analysis. (2) The error for bulk samples analyzed by XRD is unknown because the particle size of nonrespirable bulk samples varies from sample to sample. 

This knowledge is also important in order to determine if air tests conducted by OSHA compliance officers are valid. For example, if threshold limit value in the health standard is an 8-hour time-weighted average, the air sample should be obtained by sampling over the entire shift in the employee s breathing zone. It cannot be measured by a few short term samples, even if spaced over the full shift unless the worker is in a relatively fixed location with no variation in his work procedure or in the process. Such an event is generally the exception rather than the rule. 

Note in making up the chromic acid solution it is advisable to dissolve the silver nitrate separately and add it to the boiling chromic acid to prevent excessive crystallisation of the silver chromate. The chromic acid must be free from sulphate to avoid attack on the zinc. Immerse each specimen for 15 s in a 6% solution of hydriodic acid at room temperature to remove the remaining corrosion products. Immediately after immersion in the acid bath, wash the samples first in tap water and then in absolute methanol, and dry in air. This procedure removes a little of the zinc and a correction may be necessary. 

In general, three kinds of organic conpounds can be distinguished as normal constituents of air or environmental contaminants, requiring different sampling procedures for their analysis substances idiose natural state at atmospheric pressure and aid>ient temperature is that of a gas substances having sufficient vapor pressure to sublime or volatilize into the... 

The procedure in this lab is done using an air sample over water, and water vapor will saturate and add to the pressure. So, the water vapor pressure must be subtracted from the barometric pressure. You will consult the CRC Handbook of Chemistry and Physics to determine water vapor pressure at the temperature of the water being used in the activity. 

French and European Union legislation relating to the control of emissions in the workplace is examined, with particular reference to the rubber processing industry. Air sampling and analytical procedures used in the detection of nitrosamines formed in vulcanisation reactions are reviewed. 2 refs. 

WAUTERS, E., E.WALRAVENS, E.MUYLLE and G.VERDUYN (1983). An evaluation of a fast sampling procedure for the trace analysis of volatile organic compounds in ambient air. Environm Monitor.Assessm. 3, 151-160. 

Clark Al, McIntyre AE, Lester JN, et al. 1982. Evaluation of a Tenax GC sampling procedure for collection and analysis of vehicle-related aromatic and halogenated hydrocarbons in ambient air. J Chromatogr 252 147-157. 

The procedures employed for the liquid, soil, water and air samples are described and discussed below. 

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