Pumps, air sampling

Sample bag A. bag made from an inert polymer such as Teflon, complete with a fitting for connecting to an air-sampling pump. 

Air sampling pumps should be calibrated and the planned flow rate should be set prior to using them in the study. The calibration of these air pumps should be accomplished with an air sorbent tube in place, which is similar to the type to be used in the study. Records on the calibration of the air pumps should be kept in the field research notebook for the study. 

Air sampling pumps should be checked for flow rate after the completion of the exposure replicate. Some researchers use the air tubes in the test to check the flow rate of the pump with which it is associated and others use a representative air tube to check the air pumps post-exposure. It is not clear which method is best. However, using the test air tubes to check the flow rates post-exposure has some disadvantages in that the tubes may be cross-contaminated from too much handling, or samples may be mixed up for the same reason. 

Field-fortified air tubes or filters attached to air sampling pumps should not be placed on tables having other spiked matrices since volatilization of the active ingredient from the other matrices may lead to contamination of the spiked air samples. 

The apparatus shown in Figure 6, used for determining recoveries of TRIS on various sorbents, was comprised of three basic sections. The glass beads in Section A were spiked with TRIS and heated to 100°C while maintaining a flow rate of 3.7 J/min air through the beads with a Nutech Model 221-lA air sampling pump (Nutech Corp.,... 

Development of a Diffusion Head Sensor Cell. The use of air sampling pumps in portable electrochemical gas detection apparatus introduces potential problems into the instrument. First, the sensor cell response is dependent on gas flow rate. The sample flow rate, therefore, must be accurately controlled to obtain reproducible results, or the sample flow rate must be set high enough to insure a flow independent response. Secondly, failure of the pump itself could prevent a sample from reaching the sensor cell. Thirdly, the pumps are usually one of the largest users of current in a portable instrument and thereby limit usable battery life. 

The need for an air sampling pump can be eliminated by use of a diffusion tube having a set length to diameter (L/d) ratio in its geometry for introduction of a gas sample. Proper selection of the geometry and L/d ratio of the diffusion tube results in an electrochemical cell with a response which is independent of external gas flow rate. A schematic of a solid polymer electrolyte diffusion head sensor cell is shown in Figure 13. 

Estimates of inhalation contact exposure can be made by sampling air in the breathing zone of the applicator. Filter pads attached to respirators can be presumed to trap the pesticide which would have otherwise been inhaled and they can be removed and. analyzed. A second method is to use personal air sampling pumps in which air is drawn over a suitable absorbent material which can subsequently be analyzed for pesticide. 

Using the air sampling pumps, the flow rate of air through the cartridge and the duration of the sample period are both related to the concentration in the cartridge as follows ... 

Air sampling for occupational exposure to pesticides normally consists of measurement of pesticide concentrations in the worker s breathing zone, with a portable air-sampling pump and a sampling train which includes some type of collection device. The latter device, or sampling media, selected are based on the physical and chemical properties of the compound to be measured. Field workers may be exposed to chemical vapors, solid particulates or water-based aerosols. Examples of sampling media include membrane filters, sorbent tubes, polyurethane foam and charcoal. A discussion of pesticide exposure provides a useful review of methods for respiratory exposure measurement (Nigg etal, 1990). 

Air sampling pumps may be self-metering, that is, they have a metering device built in. The pump may be operated by a programmable computer to set start/stop times and for intermittent, repeated, or continuum sampling (Figure 26.2). The one shown has an isothermal flow sensor. Fluctuations in temperature or pressure are automatically corrected for. The sampling data can be downloaded to the computer. 

As well as direct-reading tubes for short-term measurements, tubes are also available for long-term monitoring. Here, the air sample is sucked through the tube by use of a personal-air-sampling pump (PAS-pump). These all look more or less the same and have a similar kind of indication to that of short-term tubes.Their area of application corresponds to that of PAS procedures (see Section 6.9.1.4.1). In contrast to these, the concentration can be read directly at the end of monitoring. Personal exposure is calculated based on the air volume pulled through. 

It was the intent of this study to determine both inhalation as well as dermal exposure. Concentrations of pesticides encountered through inhalation were measured using a Bendix model BDX44 personal air sampling pump. Air flow rates were established in the laboratory and frequent checks of the rotometer flow rate and adjustments in rates were made as needed to maintain a constant air flow volume throughout the field study. 

Just before sampling, the ends of the tube are snapped off and the end of the tube nearest the smaller 50-mg section of charcoal is attached with tubing to an air sampling pump. Air is drawn at a specific rate over a defined period, such as 200 mL/min for 4 hours. Afterwards, the tube is capped and returned to the laboratory for analysis. A solvent such as carbon disulfide is added to each section of charcoal and an aliquot of each desorbed sample is analyzed using gas chromatography with flame ionization detection. Results are reported in p,g/L or ppm. 

Portable, powered air-sampling pumps draw air through a variety of collecting devices. Calibration ensures the devices accurately measure the volume of air drawn through them. Some collectors contain an adsorbent material (usually charcoal or silica gel) that accumulates the substance. After collection, samples are analyzed in a variety of ways to assess the type and concentration of contaminants. 

Finally, one air sampling pump with All the features 212 J.J. Keller Associates www.kelleronline.com 24 245 Therm Omega Tech Inc. www.thermomegatech.com 10... 

Active personal exposure samples were at an approximate rate of 30% of the total. Active personal exposure samples were eolleeted when wind speeds were below 25 ft/min (feet per minute) or above 750 ft/min. The sampling method was eonsistent with OSHA ID-140 and employed low flow air sampling pumps with sorbent traps consisting of two beds of FSTM media which were analyzed by the FGS using the same method as that used for the analysis of the passive sample media. 

Q. If an employee stays at work after normal work hours to prepare for the next day s tasks and is injured, is the case work-related For example, if an employee stays after work to prepare air-sampling pumps and is injured, is the case work-related ... 

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