(a) Each system protecting a space with greater than 6,000 cubic feet gross volume or a space less than 6,000 cubic feet gross volume without a suitable horizontal escape route must have a pneumatic pre-discharge alarm and time delay.

1. (1) The time delay period must:

   1. (i) Last at least 20 seconds;
   2. (ii) Be approved by the Officer in Charge, Marine Inspection during system installation; and
   3. (iii) Provide enough time for one person to walk from the farthest area of the protected space to the primary exit.
2. (2) The time delay device must be pneumatically operated and have an accuracy of −0/+20 percent of the rated time delay period throughout the operating temperature range and range of delay settings.

(b) The pre-discharge alarm must:

1. (1) Sound for the duration of the time delay;
2. (2) Be conspicuously and centrally located in the protected space and marked as required by 46 CFR 97.37-9;
3. (3) Depend on the extinguishing agent, gas from a pilot cylinder, or a nitrogen cylinder specifically provided to power the alarm for its source of power; and
4. (4) Be audible over running machinery.