Hoods ventilation

Wear protective eyeglass (goggles with hooded ventilation) as a minimum. 

If the contaminant cannot be placed in a hood and must be used in an open area or room, dilution ventilation is necessary. Unlike hood ventilation, where the airflow prevents worker exposure, dilution ventilation always exposes the worker but in amounts diluted by fresh air. Dilution ventilation always requires more airflow than local ventilation operating expenses can be substantial. 

When less protection is required, it can be provided by a face shield either attached to a hard hat or held in position by a head harness that allows the shield to be tipped back when not in use. Flexible fitting chemical goggles with hooded ventilation can be used for direct protection of the eyes. 

Shut off all possible sources of ignition. Instruct others to maintain a safe distance. Wear breathing apparatus, eye protection, laboratory coat, and butyl rubber gloves11. Cover with a 1 1 1 mixture by weight of sodium carbonate or calcium carbonate, clay cat litter (bentonite), and sand. Transfer to a large dish and let evaporate in fume hood. Ventilate area well to evaporate remaining liquid and dispel vapor. Treat solid residue as normal refuse.3 12... 

SPILL CLEAN-UP for small quantity, sweep onto paper, or other suitable material, place in appropriate container, and bum in safe place (such as fume hood) ventilate area reclaim large quantities. 

FIGURE 39.9 Heat-flow diagram of (a) an open hood ventilated by convection (b) a unit with totally enclosed vapor hood. (Courtesy of J.M. Voith GmbH, Heidenheim an der Brenz, Germany.)... 

Most written material on laboratory ventilation concentrates almost exclusively upon fume hoods. Ventilation does play an important part in the proper performance of hoods, and they, in turn, usually... 

Does the work need to be done in a chemical hood, ventilated cabinet or a glove box to provide the needed level of containment ... 

Fume cupboards, slot captor or receptor hood ventilation. These must be driven by a suitable and adequate fan, and will often need water wash, dust filtration or precipitators built in. Local air pollution control requirements may require capture of vapours, which cannot simply be discharged fiom an exhaust vent. The ventilation system pressures should be checked regularly to spot obstmctions or reductions in fan performance, and the pressure figures recorded. 

Dust control includes both external and internal methods. Source ventilation, hood ventilation, and room ventilation are typical external methods. Interned methods include reactor ventilation and the use of a closed charging system, which provides a suction transfer of powder into an evacuated reactor. Dust control equipment should be interlocked with production machinery to assure simultaneous operation and protection. 

Hoods ventilate chemical process equipment by capturing emissions of heat or air contaminants, which are then conveyed through ductwork to a more convenient discharge point or to air pollution control equipment. The quantity of air required to capture and convey the air contaminants depends upon the size and shape of the hood, its position relative to the points of emission, and the nature and quantity of air contaminants. 

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