BS EN 54-20-2006 pdf download.Fire detection and fire alarm systems Part 20 : Aspirating smoke detectors.
If variations in these parameters have a significant effect on a measurement, then such variations shall be kept to a minimum during a series of measurements carried out as part of one test on one specimen.
6.1.2 Operating conditions for tests
If a test method requires a specimen to be operational, then the specimen shall be connected to supply and monitoring equipment with characteristics as required by the manufacturers data. Unless otherwise specified in the test method, the supply parameters applied to the specimen shall be set within the manufacturers specified range(s) and shall remain substantially constant throughout the tests The value chosen for each parameter shall normally be the nominal value, or the mean of the specified range.
Where an aspirating smoke detector has multiple sensitivity settings, the sensitivity of the DUT during all tests in Table 3 (with the exception of the fire sensitivity test in 6.15) shall be set at the highest sensitivity setting used during the fire sensitivity test(s).
NOTE It is not intended that the environmental tests are conducted at all possible sensitivity settings, only at the highest used during the fire sensitivity test. This is particularly relevant where multiple classes andior multiple conflguratons are submitted.
To allow the flow monitoring function to be checked as required before, during andlor after environmental tests, the sampling device may be simulated by a simpler sampling device (e.g. stub pipe with appropriate orifice(s)) to providing a typical airflow through the detector.
During the dry heat, damp heat and cold tests, a sufficient length of pipe shall be installed in the chamber to allow the temperature of the test aerosol entering the DUT to stabilize at the test temperature.
The details of the supply and monitoring equipment and the alarm criteria used shall be given in the test report.
6.1.3 Mounting arrangements
When necessary, the specimen shall be mounted by its normal means of attachment in accordance with the manufacturers instructions. If these instructions describe more than one method of mounting then the method considered to be most unfavourable shall be chosen for each test.
6.1.4 Tolerances
Unless otherwise stated, the tolerances for the environmental test parameters shall be as given in the basic reference standards for the test (i.e. the relevant Parts of EN 60068-2 as listed in Clause 2).
If a specific tolerance or limit is not specified in a requirement or test procedure, then deviation limits of ± 5 % shall be applied.
6.1.5 Measurement of response threshold value
6.1.5.1 General
Because there are a number of different types of aspirating detectors available operating on quite different principles, which have very different ranges of sensitivity, various methods can be used to measure the response threshold value. The object of any method chosen shall be to determine a measure of the aerosol concentration, which when passing through the detector, just causes an alarm to be raised. This can generally be achieved by introducing smoke or an aerosol into the sampled air stream so that the detector is subjected to a slowly increasing concentration, and recording the concentration at the moment when an alarm is generated. Because the response threshold value is only used as a relative measurement, various parameters to measure the aerosol concentration may be used, providing that the chosen parameter is essentially proportional to the particle number concentration, for the particular test aerosol. For further information it is recommended to refer to Annex A.
6.1.5.2 Typical RTV measurement procedure
The specimen for which the response threshold value is to be measured shall be connected to measuring apparatus as recommended in Annex A. The airflow through the detector shall be controlled to a typical rate within the manufacturers specification.
The DUT shall be connected to its supply and monitoring equipment as described in 6.1.2 and shall be allowed to stabilize for a period of at least 15 mm unless otherwise specified by the manufacturer.
Before commencing each measurement the measuring apparatus and DUT shall be purged sufficiently to ensure that the new results are not affected by the previous measurement.BS EN 54-20-2006 pdf download.