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Pyle900283  
#1 Posted : 30 November 2010 14:58:15(UTC)
Rank: Forum user
Pyle900283

Im currently reviewing my companys fire risk assessment and im looking for some info.Could anyone please inform me how to calculate a minimum expected time for an evacuation.
Smith24525  
#2 Posted : 30 November 2010 15:56:29(UTC)
Rank: Forum user
Smith24525

It depends on the size and number of floors of your building. If your building has fire compartments you may utilise these as part of a staged evacuation procedure. Time must be allowed for workers or occupants to respond to the activation of fire alarms. This can be identified as time taken to:
Hear the alarm – decide what I hear.
React – considering what action to take and to begin evacuation.
Evacuate – taking action and exiting the building.

Any evacuation should, as a guide, take these factors into account and everyone should be out of the building or safe from the effects of fire (a place of safety) within two and a half to three minutes of the fire starting.
Ciaran Delaney  
#3 Posted : 30 November 2010 17:20:10(UTC)
Rank: Super forum user
Ciaran Delaney

I agree with Smith but would say that he meant to say that people should be out of the premises within 2.5 to 3 minutes of the fire alarm activating.
Alex Petrie  
#4 Posted : 30 November 2010 22:37:46(UTC)
Rank: Forum user
Alex Petrie

Dare I make a controversial suggestion: practice it?

Bob Shillabeer  
#5 Posted : 30 November 2010 23:46:03(UTC)
Rank: Super forum user
Bob Shillabeer

What has been said is not strictly true. It is from the time the fire is identified, by automatic systems or from observation. Under the fire risk assessment method produced by the Fire Training College, the fire is not identifed until it is established which can be several minutes. They use the three space prinicple, the inner space, the outer space and the point of total involvment. This allows you to measure the time needed to evacuate to a point of safety. This varies according to the number of emergency escape route you have, thier availability in the event of fire and the number of florrs/distance needed to evacuate. Alex is right practice it and measure how long it takes you to evacuate to a place of safety and then work out how long it takes and base your evacuation timing on this figure. Remember a firs takes longer to spread in a multi floor building and the higher the outbreak the more time available on floors below it. Fir risk assesment reguires some thought and common sence.
TSC  
#6 Posted : 01 December 2010 08:27:42(UTC)
Rank: Forum user
TSC

To work out your minimum expected time then you need to understand the classification for your building for what is expected i.e.
Class 'A' construction - 3 minutes
Class 'B' construction - 2.5 minutes
Class 'C' construction - 2 minutes

* These are not hard and fast times, and can be extended or reduced according to the particular circumstances but are generally accepted, I would also visit Part B fire safety element for the building regs and have you checked the building compartmentation and fire protection above suspended ceiling (if any) etc.

You can then see how many exits you have in the workplace on each level (including the width) and the number of employees to calculate your flow rate and this will give you an estimation of the time it will take to evacuate the set areas etc and if you fall into the times above.

This link gives information a bit further http://www.means-of-esca...fective-means-of-escape/

also the calculations for working this out. Hope this helps.

Regards

Karel

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