What’s more dangerous in a fire: flames or smoke?
Most would say fire, but the truth is, it’s often the smoke that kills. It spreads faster, reduces visibility, and fills escape routes long before the flames arrive. That’s why any serious fire strategy needs to focus just as much on smoke management as it does on suppression systems or evacuation plans.
Yet this critical part is regularly overlooked. Smoke and Heat Exhaust Ventilation systems, or SHEVs, are designed to control smoke spread and make evacuation possible. But far too many buildings treat them as background features instead of essential life safety systems.
If your fire strategy doesn’t include a proper review of the SHEV system, it’s missing a core component of real-world protection.
What Does a SHEV System Do?
A SHEV (smoke and heat exhaust ventilation) system works by controlling the movement of smoke during a fire. It either pushes it out through ventilation points or contains it in specific zones, keeping escape paths clearer for longer.
The biggest advantage here is visibility. People need to see to escape. Smoke blocks that. When SHEVs operate properly, they create a smoke-free layer along evacuation routes, helping occupants navigate out and emergency responders get in.
There’s also a massive impact on heat control. Fires generate extreme temperatures, which can cause structural damage or accelerate the spread. SHEVs help remove that heat, slowing the rate of escalation and limiting how far and how fast the fire moves.
In a nutshell, SHEVs make a building safer to escape from and easier to fight fires in. But they only work if they’re properly planned, installed, maintained, and tailored to the specific space.
Common Gaps in Existing Fire Strategies
Many buildings have SHEV systems installed, but that doesn’t mean they’re doing what they should. Over time, layouts change. Occupant numbers go up. Internal walls are moved. Even small refurbishments can impact how smoke would behave in a real incident.
In some buildings, the system in place was never right to begin with. Poor design choices, like placing vents too far from escape routes or failing to link the system with fire alarms, can render the whole thing ineffective. Even basic errors like failing to maintain power backup for extraction fans can lead to serious failures when it counts.
Another issue is coordination. Fire strategies need to think in systems: alarms, sprinklers, doors, vents, all working together. If one part reacts out of sequence, it can cause others to fail. For example, if a vent opens too soon or too late, it can draw smoke into areas meant to stay clear.
This is why a SHEV review isn’t something to push down the priority list. It’s not just about meeting fire code. It’s about making sure the whole strategy works as one.
When Should a SHEV Review Happen?
If a building is new, under renovation, or changing its use, a full fire strategy update should always include a SHEV assessment. But even if nothing visible has changed, systems age. What was compliant ten years ago might not meet current safety expectations.
Regular reviews are especially important in high-occupancy or high-risk environments. Even if the equipment seems fine, the layout or the way the building is used might have shifted in subtle ways that affect smoke behaviour.
It’s also worth reviewing after any incident, no matter how small. Even a false alarm or system test can reveal things that aren’t working as expected.
What a Proper Review Should Include
There’s more to it than checking whether vents open and close. A meaningful SHEV review looks at whether the system supports the building’s current fire safety goals.
It should confirm whether the type of system in place, mechanical or natural, still suits the structure and layout. Vent locations need to match current occupancy zones and smoke paths. Trigger mechanisms must respond fast enough to outpace the spread, and backup power should be tested to ensure the system doesn’t fail during a blackout.
The review should also look at how the SHEV system interacts with other fire features. If doors are creating unwanted pressure pockets or fire-resistant zones are working against smoke flow, the strategy may need adjusting.
Perhaps most importantly, it should consider how real people would behave in that space during a fire. Evacuation paths should stay smoke-free for long enough to let all occupants, including those with limited mobility, exit safely. If the SHEV system doesn’t support that, it needs to be addressed.
Don’t Let Smoke Be the Blind Spot
When we think about fire risk, we often imagine flames tearing through a building. But more often, it’s the smoke that makes escape impossible. It hides exit signs. It causes panic. It poisons the air.
That’s why a fire strategy without a current, fully reviewed SHEV system isn’t complete. It might look fine in a binder or pass a surface inspection, but in real-world conditions, it could fail in seconds.
A well-functioning SHEV system gives people time. It clears the way. It buys precious minutes that could mean the difference between life and death.
So ask the right question — not “Do we have a SHEV?” but “Is our SHEV doing what we need it to do, right now?”
Because when it comes to smoke control, assumptions can be fatal.