Your article “Safety In Numbers” about the ventilation strategy for nuclear reprocessing plants (BSj 07/08) does not clearly explain the use of the air change rate table and thus may mislead some readers.

The table provided in AECP 1054 is for guidance and the actual amount of air required to ventilate a nuclear area is based on ‘dynamic containment’, ie to ensure air is cascaded from areas of lower to higher hazard. This is based on containment velocities (generally) between 0.5 to 1m/s through engineered and advantageous openings, eg doors.

Johnathan Ian Fisher, AWE, Berkshire