Designing and installing smoke ventilation systems comes with its challenges; whilst here at Sertus we don’t install systems, our background in smoke control contracting has given us an insight into the challenges the industry faces and given us a passionate desire to help solve those dilemmas.
Here are five frequent smoke control problems and some suggestions of how to overcome them.
One of the first points that springs to mind when thinking about smoke control problems is damper compliance. Many people have a limited understanding of how smoke control dampers vary from other types of dampers and therefore what they should be looking for. With scrutiny increasing as the Grenfell Inquiry progresses, the challenge becomes only more pressing.
Smoke control dampers are designed to allow products of combustion into the shaft on the fire floor but contain them within the shaft on every other floor. If a smoke control damper isn’t compliant or fails, it will compromise compartmentation throughout the building with devastating effect.
The trouble is, damper classifications are far from easy for laypeople to understand. The first step is understanding that for a product to be classed as a smoke control damper, it must be CE marked (soon to be UKCA marked) to BS EN 12101-8. However, within this certification, there are a number of different classifications. Examples include the integrity rating (fire resistance), smoke leakage, insulation, reliability, and many more. It’s critical that the damper has the correct classification for your intended use. As an example, a 120 minute fire-rated shaft must have a damper with an integrity of 120 minutes. Another example would be a horizontally-mounted damper, this must have been tested in the horizontal position for it to be installed in that manner. We’ve written a more detailed article on damper compliance here.
So what’s the solution? We’d recommend reading Paul White’s book. It’s gives a fantastic, impartial insight into smoke control dampers, right from the basic premise of their purpose through to detailed information about classification and use-cases. It’s written in colloquial and easy-to-read language and what’s more, Paul is always willing to answer questions and assist with tricky situations. You can purchase the book on Amazon here.
When smoke control systems are designed, the leakage rate of many parts of the building are taken into consideration to ensure the correct extract rate at the damper face. In particular, the leakage of the smoke shaft - it must be within a strict tolerance. However, often the shaft isn’t properly constructed and this leads to a big problem.
The commissioning engineers arrive to commission the smoke control system and find that the extract rate at the damper face is very poor, despite the fans running at the correct speed. The only option is to remove the Roof Mechanical Pod and abseil down inside the shaft, identifying and patching up gaps.
This approach is dangerous, costly, and time-consuming and is usually right before handover - the perfect storm!
What's the solution? Pressure test the smoke shaft before installing any smoke control equipment into it. It's not very expensive and it's very quick. If leakage issues are found, they can be quickly and simply fixed through the damper openings without the need for abseilers.
Companies who can help with pressure testing are:
Condensation issues occur when rising hot air inside the building meets a cold vent (as it's in contact with the outdoor air).
This typically causes problems at the head of stair - condensation occurs ruining the building and making the stairs dangerously slippery.
It causes big problems if not addressed but it's actually quite simple to fix - the answer is to use an insulated vent in every scenario where condensation may cause problems.
Closed protocol controls
Closed protocol control systems tend to cause people problems once the building has been handed over.
First, let’s cover the difference between open and closed protocol: With an open protocol system, the manufacturers of a range of devices distribute the technical details of their protocol to third parties such as component manufacturers allowing all of them to produce compatible equipment all using the same protocol and maintenance engineers who can independently maintain the systems.
With a closed protocol system, a single manufacturer produces a range of devices and control panels that all use its own specific protocol. The manufacturer does not provide general access to the technical details of its protocol and restricts its use.
Whilst proponents of closed protocol state that it prevents people tampering with the system after install. Opponents of closed protocol say that the building owner or manager is typically tied into one or two servicing providers who can charge exorbitant maintenance fees. With more and more manufacturers embracing open protocol, it's becoming easier to avoid this situation. For a full comparison between open and closed protocol, watch this video here.
It’s hard to suggest a solution to this situation other than to check with system providers that their system meets your requirements, whether that is an open or a closed protocol system.
Cause and effects confusion
Cause and effects is the programming of a system - you have a trigger (cause) and an action or set of actions (effects). If the cause and effects for a smoke ventilation system aren't set up properly, it can have devastating effects.
As an example, a fire occurs on the second floor of a ten storey building and the vent into the shaft opens. Unfortunately, the system cause and effects have been programmed wrong, so the vent on the fourth floor opens, too. The smoke from the second floor travels up the shaft and into the fourth floor - spreading the problem from one floor into another.
There are a number of cause and effect scenarios that can cause problems:
More than one vent opens into the shaft on different floors
Vents on all floors open into the shaft
The system 'locks out' the correct shaft vents but also the head of shaft and stair vents.
The correct vent opens into the shaft but poor compartmentation means smoke leakage triggers a vent on another floor to open.
Each of these scenarios are incorrect and must be avoided at all costs - but what's the solution?
Drawing out a comprehensive cause and effects chart and agreeing this with the project fire engineer and, where necessary, gaining a third-party opinion will greatly reduce the risk of flawed cause and effects programming. If you'd like to learn more about cause and effects, check out this video.