Primary Confinement System. The primary confinement system consists of
process systems equipment and the associated off-gas system. Process
equipment failures should not cause failure of the secondary confinement
system. Process equipment should operate under process conditions that
prevent or minimize the probability of explosive chemical reactions.
Secondary Confinement System. The secondary confinement system
consists of the process cell barriers and the ventilation systems associated with
the cells. Design should consider the following features:
Secondary confinement areas should be equipped with sensors that
detect abnormal releases of hazardous material from the primary
confinement boundary and provide appropriate alarms. Commensurate
with the potential hazard, the use of redundant sensors should be
Penetrations of the secondary confinement should have positive seals to
The ventilation system should be designed to maintain a negative
differential pressure during the removal of cell covers and for normal in-
leakage at cell cover joints.
Process cells should be supplied with ventilation air from the building
ventilation system and with exhaust ventilation of sufficient capacity to
provide controlled ventilation flow as required in the event of a credible
breach in the secondary confinement barrier.
Pressure in the compartments should be negative with respect to the
building ventilation system.