BS EN 54-7:2001 pdf free.Fire detection and firealarm systems — Smoke detectors—Pointdetectors using scattered light,transmitted light or ionization.
BS EN 54-7 lf there is provision for on-site adjustment of the response behaviour of the detector then:
1) for each setting at which the manufacturer claims compliance with this standard，the detector
shall comply with the requirements of this standard, and access to the adjustment means shallonly be possible by the use of a code or special tool or by removing the detector from its base ormounting;
2)any setting(s) at which the manufacturer does not claim compliance with this standard shall only
be accessible by the use of a code or special tool, and it shall be clearly marked on the detectoror in the associated data,that if these setting(s) are used, the detector does not comply with thestandard.
NOTE: These adjustments may be carried out at the detector or at the control and indicating equipment.
4.7 Protection against the ingress of foreign bodies
The detector shall be so designed that a sphere of diameter (1,3±0,05) mm cannot pass into the sensorchamber(s).
NOTE:This requirement is intended to restrict the access of insects into the sensitive parts of the detector. lt isknown that this requirement is not sufficient to prevent the access of all insects, however it is considered thatextreme restrictions on the size of access holes may introduce the danger of clogging by dust etc. It maytherefore be necessary to take other precautions against false alarms due to the entry of small insects.
4.8 Response to slowly developing fires
The provision of “drift compensation”(e.g. to compensate for sensor drift due to the build-up of dirt in thedetector), shall not lead to a significant reduction in the detector’s sensitivity to slowly deveioping fires.
Since it is not practical to make tests with very slow increases in smoke density, an assessment of thedetector’s response to slow increases in smoke density shall be made by analysis of the circuit/software,and/or physical tests and simulations.
The detector shall be deemed to meet the requirements of this clause if this assessment shows that:
a)for any rate of increase in smoke density R, which is greater than Al4 per hour (where A is the
detector’s initial uncompensated response threshold value), the time for the detector to give analarm does not exceed 1,6 ×AlR by more than 100 s; and
b) the range of compensation is limited such that, throughout this range, the compensation does not
cause the response threshold value of the detector to exceed its initial ‘value by a factorgreater than 1,6.BS EN 54-7 pdf download.