Because ordinary cable introduces a toxic hazard in the event of fire, special cabling is required in a separate area provided for air circulation for heating, ventilation, and air-conditioning (sometimes referred to as HVAC) and typically provided in the space between the structural ceiling and a drop-down ceiling.This area is referred to as the: 

Answer options:

A. smoke boundry area
B. fire detection area
C. Plenum area
D. Intergen area

C

Inbuilding construction, a plenum (pronounced PLEH-nuhm, from Latin meaning full) is a separate space provided for air circulation for heating, ventilation, and air-conditioning (sometimes referred to as HVAC) and typically provided in the space between the structural ceiling and a drop-down ceiling. A plenum may also be under a raised floor. In buildings with computer installations, the plenum space is often used to house connecting communication cables. Because ordinary cable introduces a toxic hazard in the event of fire, special plenum cabling is required in plenum areas. Source: http://searchdatacenter.techtarget.com/sDefinition/0,,sid80_gci213716,00.html