Exhaust ventilation emergency power

Extent of emergency power supplies for lighting, communication systems, and key items of equipment (e.g. cooling facilities, reactor agitators, exhaust ventilation) and instruments/alarms. 

When these boxes are used to control highly toxic and radioactive materials, provision for emergency power is necessary to ensure continuous exhaust ventilation. In some locations, seismic safety considerations may also be necessary. 

System reliability is accomplished by 1) a separate power supply to drive the emergency exhausting equipment, 2) automatic controllers for this emergency power supply and for the ventilation dampers, and 3) emergency power-driven pumps to furnish water to the fog spray,... 

Emergency power is required to operate the exhaust ventilation and treatment systems in H-6 occupancies and H-2, H-3 or H-7 facilities where toxic or highly toxic gas is used. Emergency power must be on-line within ten seconds offailure of the primary power source. 

An emergency power system shall be provided in Group H, Divisions 6 and 7 Occupancies to automatically supply power to the exhaust ventilation system when the normal electrical supply system is interrupted (UBC 307.2.8). Only exhaust is required to be on emergency power however, the exhaust must be balanced with makeup air and, thus, some supply fans may also require emergency power, particularly in the case of critical clean-rooms. Refer to section on HVAC systems for further discussion). 

Other Recirculation or exhaust air from chemical areas is prohibited. No connection between chemical areas and other areas through ventilation system is permitted. Emergency backup power is necessary. Hoods should be tested at least semiannually or after modification or maintenance operations. Operations should be performed 20 centimeters inside hood face. 

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