No abstract

Charcoal adsorbers are used extensively in air-cleaning systems for removal of toxic/carcinogenic gases and vapors. Such adsorbers are presently in use within several fume hood and glove box systems at LLNL's Chemistry and Biomedical facilities. A cur rent project of the Safety Science Group is to establish a test procedure that will provide an in-place field ti$t for measurement of charcoal-adsorber service life (residual adsorption capacity, RAC). The experimental design of this project is twofold. First, a parallel sam pling system utilizing removable miniature charcoal cartridges has been designed and will be installed on an existing HEPA filter/charcoal adsorber unit located on an organic syn thesis fume hood. Second, a series of laboratory experiments will be performed to measure charcoal-adsorber performance under controlled conditions. Laboratory tests will then be conducted on the miniature charcoal cartridges placed in service previously. It is believed that this approach will provide a realistic body of data from both simulated and real conditions to establish the basis for subsequent in-place field testing. Theory ExperimentIt has been shown previously that charcoal adsorbers can be treated as chromatographic col umns, similar to the methodology of gas-solid chromatography.u By control of the number of active sites remaining on a known mass of char coal, a measurement can be made of the RAC of the adsorber bed. A small sample of a weakly ad sorbed gas is pulsed as a squars wave into the gas stream that flows across the adsorber. The efflu ent pulse is detected by an appropriate detector and the RAC is related to the chromatographic retention time (R.T.) of the gas. As available ad sorption sites are irreversibly covered by an ap propriate heavy adsorber, the retention time of the pulse gas decreases correspondingly. When the time of the pulse gas over a fresh bed of char coal is available, a measurement can be made of the remaining effective adsorber capacity as a pro portion of the original. Other parameters from chromatography can provide additional insight into the condition of the bed, including the shape of the effluent puis* peak and the nature and quantity of response shown toward the pulse gas chosen for testing.A schematic diagram of the in-p!ace sampling manifold is shown in Fig. 1. An array of six re movable cartridges will be installed in parallel to an existing adsorber bed. The cartridges have been designed with a capacity to vary the depth cf the charcoal bed as well as to adjust the flow pat tern in front of the adsorber to assure uniform presentation to the bed. A cartridge can be re moved or replaced without interruption of the main system flow. Finally, the flow velocity across the cartridge beds can be controlled to ensure con ditions as nearly identical to the main adsorber as possible. Upon removal of a cartridge after known sampling intervals the device is easily transported to the laboratory for subsequent experimentation. These experiments will provide an avenue to study chan...

, is divided into three major sections. The first section, Progress Reports, covers the status of activities undertaken or continuing during the period; additional reports or separate pubtications will cover the final results of these activities. The second section, Technical Notes, contains reports on interesting activities of a more limited scope on wruch further reporting is not anticipated. The third section lists recent publications. Readers who are interested in more detail may contact the authors of the reports.

This report is divided into three major sections. The first section. Progress Reports, covers the status of activities underiaken or continuing during the period; additional reports or separate publications will cover the final results of these activities. The second section, Technical Notes, contains reports on interesting ac tivities of a more limited scope on which further reporting is not anticipated. The third section lists recent publications. Readers who are interested in more detail regarding any item may contact the authors of the reports listed in the Contents. II CONTENTS PROGRESS REPORTS 1 Fire Safety j Gas Chromatographic/Mass Speclrometric Analysis of Thermal Degradation Products from Wood and Composile Burns (A. E. Lipskc and M. F. Jeffries) I Corrosion in the Experimental Ducting of the Fire Test Cell (D, G.

Charcoal adsorbers are used extensively in air-cleaning systems for removal of toxic/carcinogenic gases and vapors. Such adsorbers are presently in use within several fume hood and glove box systems at LLNL's Chemistry and Biomedical facilities. A cur rent project of the Safety Science Group is to establish a test procedure that will provide an in-place field ti$t for measurement of charcoal-adsorber service life (residual adsorption capacity, RAC). The experimental design of this project is twofold. First, a parallel sam pling system utilizing removable miniature charcoal cartridges has been designed and will be installed on an existing HEPA filter/charcoal adsorber unit located on an organic syn thesis fume hood. Second, a series of laboratory experiments will be performed to measure charcoal-adsorber performance under controlled conditions. Laboratory tests will then be conducted on the miniature charcoal cartridges placed in service previously. It is believed that this approach will provide a realistic body of data from both simulated and real conditions to establish the basis for subsequent in-place field testing. Theory ExperimentIt has been shown previously that charcoal adsorbers can be treated as chromatographic col umns, similar to the methodology of gas-solid chromatography.u By control of the number of active sites remaining on a known mass of char coal, a measurement can be made of the RAC of the adsorber bed. A small sample of a weakly ad sorbed gas is pulsed as a squars wave into the gas stream that flows across the adsorber. The efflu ent pulse is detected by an appropriate detector and the RAC is related to the chromatographic retention time (R.T.) of the gas. As available ad sorption sites are irreversibly covered by an ap propriate heavy adsorber, the retention time of the pulse gas decreases correspondingly. When the time of the pulse gas over a fresh bed of char coal is available, a measurement can be made of the remaining effective adsorber capacity as a pro portion of the original. Other parameters from chromatography can provide additional insight into the condition of the bed, including the shape of the effluent puis* peak and the nature and quantity of response shown toward the pulse gas chosen for testing.A schematic diagram of the in-p!ace sampling manifold is shown in Fig. 1. An array of six re movable cartridges will be installed in parallel to an existing adsorber bed. The cartridges have been designed with a capacity to vary the depth cf the charcoal bed as well as to adjust the flow pat tern in front of the adsorber to assure uniform presentation to the bed. A cartridge can be re moved or replaced without interruption of the main system flow. Finally, the flow velocity across the cartridge beds can be controlled to ensure con ditions as nearly identical to the main adsorber as possible. Upon removal of a cartridge after known sampling intervals the device is easily transported to the laboratory for subsequent experimentation. These experiments will provide an avenue to study chan...