BS5839-1:2025 & What it means for testing point detectors

BS 5839-1 is important because it provides essential current practice to ensure fire alarm systems are reliable, compliant with regulations, and effective in real-world emergencies. Keeping up to date with BS5839-1 is crucial for anyone involved in fire safety, as it helps maintain high safety standards and supports legal compliance across the industry.

Anyone familiar with previous BS 5839-1:2017 clause numbering will need to get used to a new clause numbering in BS 5839-1. In many cases the content has stayed the same, but it will be in a different place. When it comes to testing and maintenance, we’ve made it easy to understand the key points, with the following summaries:

To illustrate the new clause numbering, you can now find the need for a visual inspection and the examination of automatic fire detectors covered in clauses 43.2.3 and 43.3.3 respectively.

“43.2.3 A visual inspection should be made to check whether structural or occupancy changes have affected the conformity of the system to this part of BS 5839 for the siting of manual call points, automatic fire detectors and fire alarm devices. The following specific points should be verified: …

…

c) any new or relocated partitions have been erected more than 500 mm horizontally from any automatic fire detector (see 21.2.8);
d) any storage is more than 300 mm from the ceiling (see 21.2.10);
e) a clear space of 500 mm is maintained below each automatic fire detector (see 21.2.18), and the ability of the detector to receive the stimulus that it has been designed to detect has not been impeded by other means;
f) any changes to the use or occupancy of an area do not render the existing types of automatic fire detector unsuitable for detection of fire or prone to unwanted alarms; and
g) any additional fire detection and fire alarm equipment required by building alterations or extensions has been installed.”

See 43.3 Inspection and test of the system over a 12‑month period:

“43.3.3 All automatic fire detectors (including those which are concealed or relatively inaccessible) should be examined, as far as practicable, to verify that they have not been damaged, painted, or otherwise adversely affected.”

During this step, essential questions for the fire engineer include: Is the fire detector where it is meant to be according to records, or has the environmental siting changed? Have any changes affected the airflow? Is the fire detector damaged/painted/covered/obstructed to affect its operation adversely?

The functional testing of detectors is now covered in clause 43.3.5, with the different types of detectors covered in 43.3.6 to 43.3.15. As before, you are in safe hands with our Solo, XTR2, Testifire and Scorpion test solutions for the functional testing of detectors.

There have been some subtle changes to in some of the clauses, for example in 43.3.5 where it now reads “… to determine whether products of combustion are capable of passing unhindered between the protected area and the sensing chamber/elements of the detector, …”

In full: “43.3.5 A functional test should be carried out on every detector (see specific recommendations for the different types in 43.3.6 to 43.3.15) to determine whether products of combustion are capable of passing unhindered between the protected area and the sensing chamber/elements of the detector, and not simply to test the ability of the detector to sample/verify the status of the atmosphere already in the sensing chamber or to confirm the status of the sensing elements.

NOTE: The above recommendation does not stipulate the method by which unhindered passage of products of combustion is determined. It is for the manufacturer and/or maintenance company to determine the method by which it is to be established that movement of products of combustion is unhindered.”

However, it is important to stress that the wording hasn’t changed anything about the requirements during this step. In case of a fire, for example with a smoke detector, the smoke still needs to be able to enter the detection chamber from the outside.

Arguably, what could be better than a functional test that generates a stimulus such as smoke from outside of the detector and when the detector is then activated, you have actual proof that the stimulus entered the detection chamber from outside. The specific recommendations for the different types are then covered in clauses 43.3.6 to 43.3.15

“43.3.6 Every heat detector should be functionally tested by means of a suitable heat source, unless operation of the detector in this manner would then necessitate replacement of part or all of the sensing element (e.g. as in fusible link point detectors or non‑integrating line detectors). The heat source should not have the potential to ignite a fire, and live flame should not be used.

NOTE: Special equipment might be necessary in explosive atmospheres.”

“43.3.7 Point smoke detectors should be functionally tested by a method that determines whether smoke is capable of entering the detector chamber and producing a fire alarm signal (e.g. by use of apparatus that generates simulated smoke or suitable aerosols around the detector). The material used should not cause damage to, or affect the subsequent performance of, the detector; the manufacturer’s guidance on suitable materials should be followed.

NOTE: During the functional test, it is expected that the quantity of simulant introduced into the detector will be of the same order as the quantity that would be necessary to trigger a fire alarm signal; this expectation also applies if the device is being tested in a test mode.”

“43.3.11 Carbon monoxide fire detectors should be functionally tested by a method that determines whether carbon monoxide can enter the detector chamber and produce a fire alarm signal (e.g. by use of apparatus that generates carbon monoxide or a gas that has a similar effect on the electro‑chemical cell as carbon monoxide). The manufacturer’s guidance on suitable test gases should be followed, and appropriate precautions should be taken when performing the test.

WARNING. Carbon monoxide is highly toxic.

CAUTION. Some gases can cause damage to, or affect the subsequent performance of, the detector.”

Another important point to make is that BS 5839-1:2025 still requires real stimuli (smoke, heat, CO), products of combustion. Consequently, a magnet-test or self-monitoring would not meet the recommendations for a functional test.

There was another important change made for multi-sensor detectors in clause 43.3.13. In c) a subtle but significant wording change was made. Previously, it said “… Where the detection system design allows simultaneous stimuli and individual sensor responses to be verified either individually or collectively, the individual sensors may be physically tested together…”. The wording here has changed from ‘may’ to ‘should’. To comply with this sub-clause, the use of an all-in-one tester (such as Testifire or XTR2) is now required.

In full: “43.3.13 Multi‑sensor detectors should be operated by a method that determines whether products of combustion in the vicinity of the detector can reach the sensors and that a fire alarm signal can be produced as appropriate. The following specific actions should be undertaken.

a) The manufacturer’s guidance on the manner in which the detector can be functionally tested effectively should be followed.
b) Multi‑sensor detectors should be physically tested by a method that determines whether

products of combustion in the vicinity of the detector can reach the sensors and whether the

appropriate response is confirmed at the CIE.

NOTE 1 Suitable test methods for each type of sensor are as described in this subclause, e.g. for heat sensors, see 43.3.6.

c) Where the detection system design allows simultaneous stimuli and individual sensor responses to be verified either individually or collectively, the individual sensors should be physically tested together. Where the system does not allow for this, each sensor on which a fire detection decision depends (e.g. smoke, heat, carbon monoxide) should be physically tested individually.
d) Where a system includes a time‑related configuration of detection, a sensor should not be excluded from being tested as a result of the time‑dependent mode.
e) On completion of tests, the system should be returned to its normal configuration.

NOTE 2 Information regarding the configuration of multi‑sensor detectors and selection of types of detectors suitable for the application is given in Annex D, Figure D.1.

NOTE 3 Further information is given in the FIA guidance note Functional testing of point type multisensory detectors [19].”

When it comes to the testing of detectors, people sometimes simply focus on the functional testing aspect. It is easy to forget that the visual inspection and the examination of detectors on-site are part of the testing protocol and play an important role. Similarly, part of this testing approach for detectors is the LED check by the fire service engineer when physically on location and this is now covered in clause 43.3.4

“43.3.4 The correct operation of all readily visible integral and/or remote visual fire indicators should be checked. It should also be verified that visual fire indicators are not obstructed from view by changes in their environment or contaminates such as paint.

NOTE Where a remote indicator is used, it is not necessary to confirm that the out‑of‑sight fire indicator on the detector is operational.”

BS5839-1:2025 & What it means for testing point detectors

Detector Testing: A three-step approach

Why all three steps matter

STEP 1 - BS5839-1:2025 & Visual Inspection & Detector Check

STEP 2 - BS5839-1:2025 & Functional Testing of Detectors

For point heat detectors

For point smoke detectors

For point CO detectors

For Multi-Sensor detectors

STEP 3 – BS5839-1:2025 & LED Check

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BS5839-1:2025 & What it means for testing point detectors

Detector Testing: A three-step approach

Why all three steps matter

STEP 1 - BS5839-1:2025 & Visual Inspection & Detector Check

STEP 2 - BS5839-1:2025 & Functional Testing of Detectors

For point heat detectors

For point smoke detectors

For point CO detectors

For Multi-Sensor detectors

STEP 3 – BS5839-1:2025 & LED Check

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