When using registering devices, in addition to placing point sensors, a sample of the hazardous fire factor values is measured at the height of the registering device location. This is done using the “slice” mechanism of the FDS system.
Lines similar to the following are automatically added to any model:
&SLCF QUANTITY='TEMPERATURE' PBZ=1.7/
&SLCF QUANTITY='VISIBILITY' PBZ=1.7/
&SLCF QUANTITY='DENSITY' SPEC_ID='OXYGEN' PBZ=1.7/
&SLCF QUANTITY='DENSITY' SPEC_ID='CARBON DIOXIDE' PBZ=1.7/
&SLCF QUANTITY='DENSITY' SPEC_ID='CARBON MONOXIDE' PBZ=1.7/
&SLCF QUANTITY='DENSITY' SPEC_ID='HYDROGEN CHLORIDE' PBZ=1.7/
FDS system calculates the values of the physical quantities measured with the “slice” tool at the mesh nodes, dividing the calculation area into cells, i.e., at the cell vertices. Therefore, the actual height at which the “slice” of the hazardous factor values are obtained depends on the cell size and may differ from 1.7 m. For example, with a cell size of 0.5 m, the slice is calculated at a height of 1.5 m, and with a cell size of 0.25 m, the slice is calculated at a height of 1.75 m.