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CROSS Safety Report

Testing of smoke control systems

Report ID: 1099 Published: 10 March 2022 Region: CROSS-UK

This report is over 2 years old

Please be aware that it might contain information that is no longer up to date. We keep all reports available for historic reference and as learning aids.


A reporter is concerned about the way that smoke control systems in residential buildings are commissioned, installed, tested, and maintained.

Key Learning Outcomes

For facilities managers, fire risk assessors, system designers, and installers:

  • There is a need for competent people at all stages of the design, installation, configuration, commissioning, and handover
  • For those ultimately responsible for compliance with the Building Regulations at the build stage to be able to demonstrate how this has been achieved

For Responsible Persons:

  • Be familiar with the requirements of Regulatory Reform (Fire Safety) Order 2005
  • Ensure any smoke control system within their premises is configured correctly and check that this was carried out by someone who is competent to do so
  • Ensure any smoke control system within their premises is tested and maintained correctly, this should be carried out by someone who is competent to do so

Full Report

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The Full Report below has been submitted to CROSS and describes the reporter’s experience. The text has been edited for clarity and to ensure anonymity and confidentiality by removing any identifiable details. If you would like to know more about our secure reporting process or submit a report yourself, please visit the reporting to CROSS-UK page.


Smoke control systems are technical solutions to ensure the protection of life in case of fire. Their main function is to operate in case of an emergency so that no smoke will be present in access corridors and evacuation stairwells. Should a system fail to operate as designed, the consequences could be severe, which is why it's important that systems are identified as inadequate through regular checking and maintenance, before a fire occurs.

The issue reported came to light out of research conducted into the functionality of smoke control systems in existing residential apartment buildings. The programme included approximately 50 field tests, for the conduction of which the reporter requested the attendance of a smoke control or fire alarm engineer to test the cause and effect of the systems.

The presence of these professionals was requested because maintenance records offered by block managers were considered unreliable for the quality level and thoroughness of the research conducted. Similarly, the reporter is of the mind that risk assessors do not necessarily request or witness testing. Recent experience from real fires in Regents Quay in Leeds (where smoke vent shaft doors opened in additional floors and allowed the spread of smoke) and New Providence Wharf in London (where the smoke detectors failed to operate the Automatic Opening Vent) motivated the reporter to fully interrogate the systems in place.

Current technical guidance dictates that automatic opening vents (AOVs) are configured in such a way that only the vent in the fire affected floor should operate, with the rest in the remaining storeys staying closed. For example, this is articulated in BS 9991:2015 (paragraph where:

“Only the AOV leading from the protected corridor or protected lobby where the smoke has been detected should be configured to open. This should open either to external air or into a smoke shaft; all other protected lobby vents should be configured to remain closed. Fire and rescue service override controls should not permit multiple lobby vents to be open simultaneously”.

Smoke control testing, like the one carried by the reporter, involves the exposure of automatic fire detection devices to artificial smoke or the activation of point detectors in ‘fire mode’, rather than an engineering override function. This way the system deals with the incident as with a real fire. A well configured system will ‘lock out’ once a detector is activated, so that if other point detectors in other floors are activated, the vents will remain closed. These additional vents should be able to be operated again after a system reset.

Even though the analysis is ongoing, the reporter’s initial estimation is that 60% - 80% of buildings have failed cause and effect testing. The failures have been attributed to many different reasons, examples of which are that vents are opening in the wrong direction, design critical vents are not opening at all, or that many systems are not 'locking out’ allowing the operation of vent doors beyond the fire floor.

Another concern originated with one mechanical depressurisation system not clearing smoke effectively, leading to smoke pooling in corridors due to the lack of airflow in the corridor. However, the system had passed the air flow readings at the stair door and shaft vent. Re-testing of this system is pending.

A survey for further insight from groups of professionals who are involved in testing and maintenance of smoke control systems indicated that there is a lack of competency and awareness of the proper operations of these systems. Additionally, smoke control installations are not being inspected, tested, and maintained correctly, according to these groups.

The underlying causes for this issue, according to the reporter, are the lack of competent contractors in the industry, which contributes to improper installation and commissioning, and the eventual ineffectual testing and maintenance of these systems. Finally, the reporter considers that any cause and effect testing is not being completed as specified, either by block managers, contractors, risk assessors, or fire service inspecting officers.

Finally, the reporter worries that these issues may be present in other buildings beyond the area that they surveyed.

Expert Panel Comments

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This is a significant concern and a recent London Fire Brigade thematic report included research into smoke ventilation systems in existing buildings and came to similar conclusions. These issues are being identified more and more by FRSs and obviously, unfortunately, normally 'during/post fire' but some being found during audit activity.

The report does not give the reasons for the non-functioning systems but these are likely to be poor design, poor installation, poor maintenance or a combination of all three. In addition, there can be a gap in understanding between those designing such systems and those testing and maintaining them. System design can be complex. 

The report highlights two approaches to testing and maintenance of systems. One is based on simple cause and effect testing of the design. The other mentions testing the effectiveness of the system (i.e. a mechanical depressurisation system), with reference to 'smoke pooling', which infers that smoke from a fire was simulated in some way. These are different approaches to the testing of systems, and cause and effect testing in 'cold' conditions is typically done, rather than any simulation of smoke movement for practical reasons.  

The report confirms the importance of an appropriate method for testing and maintenance of these systems, as the nature of testing with smoke, to assess system effectiveness, can influence the outcome of the testing (e.g. if 'cold' smoke is used, this behaves differently to 'hot' smoke, and may not necessarily be appropriate).  Therefore, careful consideration needs to be made for appropriate testing and maintenance of these systems. 

The real issues are those of competence and understanding. A UKAS accredited 3rd party certification scheme for installers of smoke ventilation systems in residential buildings is in operation, but not all installers are members of that scheme and in addition the scheme has only been in existence in recent years so there are plenty of existing systems that would have been installed by companies that are outside the scheme.

There are no schemes available for checks on the competence of companies that carry out maintenance of smoke ventilation systems, so there is no way for facilities managers to ensure that their systems are being maintained by a competent engineer. Facilities managers and fire risk assessors must be encouraged to ensure that they do what they can to ensure that systems are fully functioning. This may require investment but as they are safety critical fire safety systems that is necessary.

It is of vital importance that any smoke control system performs as required and intended to support the fire strategy of the premises. Failure to ensure this is the case may not only lead to formal enforcement action by the relevant authority having jurisdiction but may also place persons at risk of death or serious injury in event of fire.

There are documents that can be cited in ADB (both volumes), BS 9991/9999 as well as various documents on the Smoke Control Associations website  Smoke Control Association, particularly  SCA Guidance on Smoke Control to Common Escape Routes in Apartment Buildings. 

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