Someone on a recent project asked me why we wouldn’t just run the smoke vents off the BMS. The HVAC controller was already there. The cabling was already there. It would save a panel and a power supply.
I get the question. Using HVAC controls for smoke ventilation looks like a clean piece of value engineering on paper. In practice it is one of the fastest ways to build a non compliant system, and one of the hardest to unwind once it is installed.
Smoke ventilation is a life safety system. HVAC is a comfort system. They live in the same building, sometimes in the same shafts, sometimes operating the same actuators. That does not make them the same thing, and it does not make their control equipment interchangeable.
Here are seven reasons a smoke vent system needs its own dedicated control panel, not the BMS or HVAC controller next door.
1. HVAC Controls Have No Smoke Certification
A smoke control panel for a UK life safety installation has to be aligned with ISO 21927-9 for the control function and specified against BS 7346-8 as the current UK interim compliance route until prEN 12101-9 is published as a harmonised BS EN. The power supply behind it has to meet BS EN 12101-10. Those certificates are specific. They cover the panel’s response under fire conditions, its fault monitoring, its battery backup, and the way it handles failure modes.
A BMS or HVAC controller has no such certification. It might be a good piece of kit for managing comfort ventilation, lighting, and heating. It is not built or tested for fire conditions, and the manufacturer will not put its name to an ISO 21927-9 statement because the product was never designed to that standard.
If the fire strategy, the M&E specification, or the project’s BS 9991 reference requires a certified smoke control panel, a BMS doesn’t meet the requirement. No amount of clever programming closes that gap. The certificate is the certificate.
2. The Priority Logic Is the Opposite of What You Need
This one catches people out. HVAC controls are built to manage airflow under normal conditions. When a fire alarm goes off, the standard HVAC response is to shut down the air handling units to stop the system spreading smoke through the building.
A smoke ventilation system has to do the opposite. On alarm, it needs to open vents, energise fans, run actuators to their fully open positions, and hold them there. The two systems have opposite reactions to the same trigger.
Try to wire that into a single controller and you end up writing logic that says “ignore the fire alarm input on these outputs but obey it on those outputs”, with a list of exceptions running into dozens of lines. The first time someone tweaks a setting six months later, the logic breaks silently. Nobody sees it until the next test.
A dedicated smoke control panel handles the fire alarm input as its primary purpose. Its default state on activation is the safe state for smoke ventilation. That isn’t a feature you add. It is the way the panel is built.
3. Reliability Classification Is Different
HVAC and BMS equipment is built to a comfort reliability standard. A BMS that drops out on a Friday afternoon and reboots on Monday morning is annoying. Nobody dies.
A smoke control panel cannot drop out. It has to keep running on mains, fall over to battery on mains loss, monitor itself continuously for faults, and report any fault to a manned location within a defined timeframe. The fault categories are specific. The battery autonomy is specific. The monitoring is specific. All of it is set by BS EN 12101-10 and the panel’s alignment with ISO 21927-9.
You can’t bolt those requirements onto a BMS. The processor, the power supply, the firmware, and the fault monitoring would all have to be rebuilt to a different standard. At that point you are not saving a panel. You are paying twice for a worse version of the panel you should have installed in the first place.
4. Cause and Effect Drifts the Moment HVAC Settings Change
Here is what happens on a building two years after handover. The BMS contractor comes back to retune the heating because tenants are complaining. They adjust a few ventilation schedules. They add a new zone for a meeting room that was reconfigured. They update some setpoints.
If the smoke vent cause and effect is buried in the same controller, every one of those routine HVAC changes is a potential modification to the life safety system. The BMS engineer doesn’t know that. They are working on a comfort job. They make a change, the smoke logic drifts a fraction, and the system is no longer doing what the fire strategy says it should.
You will not catch it on a visual inspection. You will catch it on the next annual test, if you are lucky, and on the next incident if you are not.
A separate smoke control panel doesn’t drift when the BMS gets retuned. The two systems are physically separate. The cause and effect on the smoke panel is the cause and effect that was commissioned, until somebody with the credentials to change it deliberately changes it.
5. You Cannot Build a Golden Thread Across Two Systems
The Golden Thread under the Building Safety Act 2022 requires a structured, digital, continuously updated record of every safety relevant change to the smoke control system. Every cause and effect tweak, every commissioning record, every test result, every modification, all attributable to a named user with a timestamp and a reason.
A BMS does not produce that record for the smoke logic, because the BMS treats the smoke logic as part of a wider HVAC programme. The change log on a BMS records what the BMS engineer changed. It does not separate out which of those changes affected the life safety functions, who authorised them, and how they were verified after the change.
You end up with a 4,000 line audit log of BMS changes and no way to extract the fire safety thread out of it. The Building Safety Regulator will not accept that as Golden Thread evidence. The Accountable Person cannot rely on it. The Responsible Person cannot rely on it.
A dedicated smoke control panel with secure software configuration, such as the O Range family running O Range Connect, produces a Golden Thread record by default. Every configuration change is logged against an authenticated user. Every test event is captured. The record exports as evidence, not as 4,000 lines of context you have to filter.
That is the difference between a control system that supports compliance and a control system that creates an evidence gap you can’t close.
6. The Maintenance Regimes Don’t Match
HVAC and BMS equipment runs on a service interval driven by mechanical wear, filter life, and software updates. A typical interval is six monthly, occasionally quarterly on heavy use sites.
A smoke ventilation system runs on a different regime. Daily indicator checks. Weekly function tests on certain components. Monthly tests of the AOVs. Annual full system tests with documentation in line with BS 9991 and BS 9999 maintenance provisions and BS 7346-8 commissioning records. The intervals exist because a system that only operates under fire conditions has to be proven ready, on a schedule, by competent people.
If the smoke control function is sitting inside the BMS, it does not get tested on the smoke control schedule unless someone deliberately writes the schedule, briefs the BMS contractor, and arranges access for the smoke control engineer to ride along with the BMS service. In my experience that happens about a third of the time on integrated systems. The other two thirds, the smoke side falls into the BMS service interval and the annual test reveals the gap.
Two different systems means two different maintenance regimes, performed by two different competent contractors, with two separate certificates. That is a feature, not a duplication.
7. The Responsible Person Cannot Discharge the Duty
This is the one that should end the argument on its own. Under the Fire Safety Order, the Responsible Person has a non delegable duty to keep fire safety equipment in effective working order. Under the Building Safety Act, the Accountable Person has a parallel duty for the building’s safety case.
You cannot discharge that duty through a control device that was never built, tested, or certified as fire safety equipment. The BMS contractor is not signing an ISO 21927-9 statement. The HVAC manufacturer is not warranting fire performance. The M&E designer who specified the integration is not the Responsible Person.
When something goes wrong, the Responsible Person is the one in front of the Building Safety Regulator or the coroner. The chain of certification has to lead from the installed equipment, through a recognised standard, to a named manufacturer. A BMS doing smoke control breaks that chain at the first link.
I have sat in post incident reviews where this exact issue came up, and the saving from skipping the dedicated panel had long since been overtaken by the legal and insurance fallout from the integration. It is not a saving. It is deferred cost with interest.
How HVAC and Smoke Ventilation Should Integrate
None of this means the smoke control system has to be isolated from the rest of the building. Integration with HVAC and BMS is fine, and often necessary. The principle is that the smoke control panel is the primary control device for the life safety function, and the BMS receives status signals from it, not the other way around.
The smoke panel runs the cause and effect. The smoke panel handles the fire alarm input. The smoke panel logs configuration changes. The BMS sees what the smoke panel is doing through a monitored interface, and the BMS can report status to a head end, but it can’t drive the actuators when there is a fire.
That gives you all the benefits of central monitoring without any of the certification, drift, or duty problems. It costs a panel and a power supply. It saves a building.
If you are scoping a project right now and a designer is suggesting that the BMS will handle smoke control, push back. Get the certification question on the table early. The cost of changing direction at scheme design is small. The cost of changing direction after handover is significant, and it always falls on the building owner, not the people who recommended the shortcut.
Further Reading
- How Smoke Ventilation Integrates With Other Building Systems
- The Golden Thread, Smoke Ventilation, and the Building Safety Act
- Primary Zone Lockout Explained
- Why Dip Switches Are Killing Your Golden Thread Compliance
Ready to Specify a Dedicated Smoke Control Panel
Vent Trade supplies the O Range smoke control panel family, aligned with ISO 21927-9 and specified against BS 7346-8, with BS EN 12101-10 power supplies and full Golden Thread audit logging through O Range Connect.
Call us on 01202 725 689 or email info@vent-trade.co.uk to talk through the specification on your project. If a BMS integration is already on the drawings, we can help you work out what stays on the BMS and what needs to come back to a dedicated panel.
Alan Riggs, New Business and Customer Relationship Manager, Vent Trade
