Fire Evacuation Times: How Long Is “Long Enough”?
One of the questions I get asked regularly after a fire drill is, “How long should it take to evacuate the building?” And while it sounds like a simple enough question, the answer is anything but — especially within the framework of the UK’s risk-based fire safety legislation.
There’s No Magic Number — and That’s the Point
The Regulatory Reform (Fire Safety) Order 2005 doesn’t give us a set time to aim for. Instead, it says that people must be able to evacuate “as quickly and as safely as possible.” Why no stopwatch in the law? Because every building is different — office blocks, warehouses, schools, care homes — each comes with its own unique risk profile, design features, and occupancy patterns.
Instead, the guidance places emphasis on ensuring that escape routes are designed to allow people to get out before conditions become life-threatening. That means fire safety needs to be factored in right from the design stage — with compliance to standards like Approved Document B, BS 9999, and BS ISO 20414 baked into the process.
It’s Not Just About Doors and Corridors
Good escape design is about more than just ticking boxes. You need:
- Enough exits and escape routes
- Acceptable travel distances
- Protection from smoke and fire
- A robust, early-warning fire detection system
And you need to consider human behaviour. We know that people don’t always evacuate the moment the alarm sounds. In fact, studies show that as much as two-thirds of evacuation time is lost to delay — people finishing up what they’re doing, waiting for confirmation, or assuming it’s a false alarm.
That’s where we get into ASET and RSET:
- ASET (Available Safe Escape Time): the time between ignition and the point when conditions become untenable
- RSET (Required Safe Escape Time): the time it takes for people to become aware, react, and evacuate
The golden rule? ASET needs to be comfortably longer than RSET.
The “Real World” Complicates Things
In theory, we can design to achieve this. But in reality, things like broken detectors, blocked exits, damaged fire doors, layout changes, and poorly maintained systems all chip away at your safety margin. Add to that behavioural issues — like people ignoring alarms or unfamiliarity with routes — and it becomes clear why regular, honest fire risk assessments are critical.
A robust assessment will consider:
- Past evacuation drill timings
- Whether procedures were actually followed
- Who might need help getting out
- The condition of your escape routes
- The type and reliability of your alarm system
- The general fire safety culture in the building
My View?
Ultimately, your goal is to ensure every person can reach a place of safety before conditions deteriorate. That means understanding the design limitations of your building, how people really behave in an emergency, and where your current setup might fall short.
It’s not about achieving a specific time — it’s about having the confidence that your fire strategy holds up when it matters most.
If you’re unsure whether your current evacuation strategy truly holds up under pressure — don’t leave it to guesswork. Get in touch with Sanjay on 01748 811992 or email at hello@firesafetycompany.com and let’s review it properly.
Whether it’s a full fire risk assessment, a review of evacuation timings, or a deep dive into ASET vs RSET for your site, I’ll help you identify any weak points before they become real risks.Your people rely on you. Let’s make sure your evacuation plan is correct!
