Badge samplers charcoal

Advantages and disadvantages of thermal desorption are listed in Table 9.3. (Charcoal badges are also available which require no pump these are termed passive samplers .) Instruments are also available to give direct readout of atmospheric levels of pollutant. 

Abcor "Gasbadge" organic vapor samplers and 3M 3500 Organic Vapor Monitors were purchased for use in this study. Abcor badges were loaded prior to each field trip in an office environment. Standard SKC charcoal tubes (100 mg collection section with 50 mg backup) were used, with DuPont P-200 pumps calibrated prior to each survey. 

As for workplace monitoring, there have been two main types of diffusive sampler used for monitoring of indoor air (i) badge type samplers containing a strong adsorbent such as charcoal that requires solvent desorption for GC analysis and (ii) tube type samplers with weaker adsorbents such as the porous polymer Tenax that can be thermally desorbed. The samplers most widely used have been developed for monitoring of workplace atmospheres and applied to indoor air through modification of the exposure period and the analytical method. 

The most widely used badge type sampler for indoor air studies has been the OVM 3500. This is a circular badge with a 1-cm diffusion length containing a charcoal wafer. Desorption of VOCs is carried out within the monitor itself by the addition of carbon disulfide. Exposure periods applied have ranged from 24 h to 3 weeks. The diffusive uptake rates reported by the manufacturer for 8-h exposure periods are about 30 ml/ min, but actual values are compound specific. For the monitoring of hexane in the workplace, the diffusive uptake rate is not significantly affected by ambient air movement, provided that there is a minimum air velocity of about 0.1 m/s (HSE, 1992). 

One important consideration is the possibility of reuse of thermal desorption tubes, since they are cleaned in the desorption step. Charcoal badge-type samplers are of single-use nature but cheaper. Solvent desorption also allows multiple analyses from a single sample to give greater accuracy. 

Table 1 Compounds validated using the SKC Inc 575 series badge-type sampler with (A) charcoal and (B) Anasorb 747 sorbents...

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