Detector Head Replacement

Time for a Change!

Get yourself a new detector head for your KRM® duct smoke detector.

Our KRM® series has been available since September 2010. This means that the first devices are now approaching 8 years of service. We would like to remind you that they will then also have reached the end of the statutory 8-year replacement period.

Please note the following information.

If you should have any questions, feel free to contact our field service or turn directly to our headquarters. You will find your sales representative’s contact information on our website under Contact.

Info sheet

Duct smoke detectors such as our KRM® operate as smoke trigger devices equipped with a DIN EN 54-7-tested fire detector (or „detector head“) in both their VDS-tested version and their DIBT version. These fire detectors operate with the use of an optical detector chamber, which detects diffused light. 

Type testing of fire detectors in accordance with DIN EN 54-7 involves determination of the response threshold. The fire detector should trigger neither too early (interference resistance, false alarm immunity) nor too late. This requires an extremely involved test procedure. Testing with a test spray, by comparison, can at best provide a rough orientation and should only be used for regular inspection purposes.

Over the course of time the sensor and electronic hardware are subject to diverse environmental influences such as temperature and climate fluctuations (vibration of the ventilation duct) and chemicals. This leads to changes in the detector’s performance characteristics. Dust, moisture and insects (soiling) may also impact  on the fire detector.

All this affects the sensitivity of the fire detector and can do so in either direction. This cannot be predicted with any certainty. Thus it is a measurable fact that fire detectors delivered new or returned from in-factory inspection show response values that differ from those of a fire detector that has been in service for a while. Soiling compensation can only correct this to a certain extent. Fire detectors thus classify as wearing parts which require regular replacement.

had some of their components (wearing parts) replaced DIN EN 54-7 still requires a test to check that their response behavior has not been altered or is still within narrow tolerance limits. This kind of test cannot be done on site, since there are currently no systems available for this purpose and it would also be too expensive. After the exchange of parts or cleaning or replacement of the entire detector chamber the fire detector still has to be reset and recalibrated. This cannot be done by field service technicians on site in the manner prescribed by the DIN EN 54 standard series.

Vacuuming or blowing out the detector is not a suitable method of restoring the detector to its factory condition because this poses a risk of damaging parts of the optical detector chamber, possibly resulting in false alarms or delayed triggering.

For this reason fire detectors built into duct smoke detectors must be regularly replaced at the following intervals (service life!) (see also DIN 14675 on fire detector systems, DIN 14677 on arrest systems and the recomendations of ZVEI Information Sheet 33005:2010-06 and AMEV BMA 2013, amongst other guidelines):

Case 1) Every 8 years at the latest (service life)*

Fire detectors with automatic soiling compensation

built into our KRM® series
fire detector RM 3.3

Case 2) Every 5 years at the latest (service life)*

Fire detectors without automatic soiling compensation.

built into our UG2 series
fire detector STP-DA

Depending on the degree of soiling it might be necessary to replace the fire detector much earlier. Observe indicator in device.

Tip: Write the date of first use and/or the replacement due date somewhere on the fire detector. The date of manufacture of our duct smoke detectors, indicated on the type plate on the outside of the housing, can serve as a rough orientation.

Catalogue price list 2020














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