# Number of parallel systems in the same confinement

Number of identical, parallel, and identically loaded systems in the same confinement such as in a common duct, in a tunnel (method IEC 60287-2-3) or on the same tray or ladder.

Symbol
$N_{sys}$
$T_{4t}$
$T_{a}$
$T_{s}$
$T_{t}$
$\theta_{at_{L}}$
$\theta_{at_{z}}$
$\theta_{o_{L}}$
$\theta_{o_{z}}$
$\theta_{t_{L}}$
$\theta_{t_{z}}$
$W_{a_{L}}$
$W_{a_{z}}$