http://www.documentbays.org/89987-bs-en-50291-1-2018.html

5.5.3 Inbuilt testing of end-of-lifeThe manufacturer shall submit to the test house, and retain evidence of, the methodology and any supportingcalculations which demonstrate the operation of the inbuilt testing of the end-of-life detection. This shall be afully automated process.The manufacturer shall submit to the test house, and retain evidence of, evidence that the frequency of testingis sufficient to detect the end-of-life, within 30 days of its occurrence.5.5.4 End of life fault warningsThe end-of-life indication shall utilize either the visual fault warning or a separate end-of-life visual indicator.NOTE The end-of-life audible indication should be clearly different from the gas alarm indication – see Annex C foran example.5.6 Fault warnings5.6.1 The apparatus shall provide an audible and visible fault warning within 10 min of loss of continuity orshort circuit to the sensor if the sensor is replaceable or within 1 day if the sensor is non-replaceable.5.6.2 The audible fault warning shall be clearly identified and different from a gas alarm.5.6.3 The visual fault warning shall be as per 5.3.3.5.6.4 The audible low battery warning shall be clearly identified and different from a gas alarm.5.7 Alarm silence facility (optional)5.7.1 The provision of a manually operated alarm silence button is optional.5.7.2 The alarm silence button may be combined with the fault warning silence button (see 5.8) and the testbutton.5.7.3 In an alarm condition the operation of the alarm silence button shall silence the audible alarm signalonly. The visual alarm signal shall not be suppressed.5.7.4 The audible alarm signal shall reactivate within 15 min from the time the alarm silence button isoperated where the concentration of carbon monoxide surrounding the alarm remains at 50 ppm CO orgreater. Continuous operation of the alarm silence facility shall not lead to the apparatus being silenced formore than 15 min without the audible alarm being reactivated.5.7.5 It shall not be possible to create a silent period unless the apparatus is already in the alarm condition.5.7.6 It shall not be possible to silence the alarm at concentrations above 300 ppm.5.7.7 The user manual shall state that any remote silencing feature shall only be used in line of sight of theCO alarm.5.8 Fault warning silence facility5.8.1 The provision of a manually operated fault warning silence button is optional.The alarm silence button may be combined with the fault warning silence button and the test button.5.8.2 In a fault condition the operation of the fault silence button shall silence the audible fault signal only.The visual fault signal shall not be suppressed.5.8.3 The audible fault warning shall reactivate within 24 h from the time the fault warning silence button isoperated. Continuous operation of the fault warning silence facility shall not lead to the apparatus beingsilenced for more than 24 h without the audible fault warning being reactivated.5.8.4 It shall not be possible to create a silent period unless it is already in the fault condition.5.8.5 The fault warning silence button may be combined with the alarm silence button and the test button.5.8.6 If the fault warning silence facility is activated, it shall not inhibit the audible alarm signal.5.8.7 The user manual shall state that any remote silencing feature shall only be used in line of sight of theCO alarm.