Technical/Programming Manual
FT1020G3 Rev 2.2.1
106
3. The decision value has here reached the pre-warning level and pre-warning is
activated.
4. The decision value is here below the pre-warning level and the pre-warning is
automatically reset.
17.4.3
Smouldering smoke algorithm
The smoke from a smouldering fire causes the sensor value to rise very slowly but not
reach the fire alarm level. A smouldering fire can last for hours and sometimes days. The
smouldering smoke algorithm will detect such a fire at an "early" stage.
The smouldering smoke algorithm is dependent on and works in parallel with the selected
alarm algorithm, i.e. the smouldering smoke algorithm can affect the pre-warning and fire
alarm levels, see below.
If the decision value has been over the smouldering level for
7 minutes
(1-2 in the figure),
the pre-warning and fire alarm levels will be lowered:
The pre-warning level will be lowered to a level right between the original pre-
warning level and the smouldering level.
The fire alarm level will be lowered to a level right between the original fire alarm
level and the pre-warning level.
If the decision value has reached the pre-warning level, but not the fire alarm level, after
additional 90 minutes
(2-4 in the figure), the pre-warning and fire alarm levels will be
lowered again:
The pre-warning level will be lowered to the original smouldering level.
The fire alarm level will be lowered to the original pre-warning level.
If the decision value continues to rise, fire alarm will be activated (5 in the figure).
The smouldering smoke algorithm will be aborted and the pre-warning and fire alarm levels
restored to their original values if:
The decision value becomes lower than the smouldering level.
The decision value, after the
90 minutes
, has not reached the pre-warning level.
The decision value, after the
90 minutes
and
additional 120 minutes
, has not
reached the fire alarm level.
The smouldering offset can be set in EBLWin for all detectors collectively, see chapter
"Alarm algorithms", page 153.
Figure 38 Smouldering smoke algorithm example for 4301.