Local ventilation modes

All local ventilation systems can, in principle (and many are in practice), be manufactured for use in one or more of three different modes fixed, flexible, and mobile. 

It is difficult to determine the most common mode for local ventilation and naturally many systems fit into more than one mode. 

PERSONAL PROTECTION Wear impervious protective clothing, including rubber gloves, lab coat, apron or coveralls wear chemical safety goggles or face shield enclose operations and/or use local exhaust ventilation at site of chemical release use self-contained breathing apparatus operated in positive pressure mode maintain eyewash baths and safety showers in work area. 

PERSONAL PROTECTION wear clean body-covering clothing and protective gloves use dust- and splash-proof safety goggles appropnate respirators are needed in areas where exposure would be above the permissible exposure level a system of local and/or general exhaust ventilation is recommended in the event of a fire, wear self-contained breathing apparatus with full face-piece operated in positive pressure mode maintain eyewash fountains and quick-drench facilities in work area. 

Protection from isocyanate vapours liberated during polyurethane manufacture is usually achieved by installing permanent exhaust ventilation units which either exhaust directly to the atmosphere or pass their exhaust fumes through scrubbers which extract the isocyanate vapour through a sodium carbonate spray tower before atmospheric exhaustion occurs. Continuous vertically positioned exhaust hoods are common where continuous conveyor lines are involved for localized extract situations, vertical down-draught or horizontal extract modes are much safer for operatives, being designed to remove all isocyanate vapour away from an operative s face and body. These latter situations apply particularly in the manufacture of cast-moulded and reaction-injection moulded products. 

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