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Smoke control design to CEN/TR 12101-5

Paul Compton

Colt International Limited

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CEN/TR 12101-5:

Smoke and heat control systems – Part 5: Guidelines on functional recommendations and calculation methods for smoke and heat exhaust

systems.

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Contents

Introduction

How to use the TR

Results

The future

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History

Based on British design methods:

-Fire papers 7 & 10 1963 & 1964

-BR 34 1979

-BR 186 1990

-BR 258 1994

-BR 368 1999

-BS 7346-4 2003

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Why a CEN/TR?

A CEN/TR is a Technical Report.

It does not have the same authority as an EN.

It is used when there is insufficient agreement for an EN.

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Purpose of the TR

Guidance to designers on function

and steady state calculation of SHEVS.

Doesn’t cover equipment selection or installation (CEN/TR 12101-4).

Gives zoning, mass and volume flow rates, aerodynamic area of exhaust and inlet and minimum number of exhausts.

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Time

Fir

e S

ize

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Weaknesses

Limited guidance on fire size.

Not very user friendly layout.

Best spill plume calculation is difficult to use.

More research is needed to improve some calculations.

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Who should use CEN/TR 12101-5

Intended for people with suitable understanding, knowledge and training.

Authorities checking designs also need knowledge so they can do more than simply check the maths.

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How to use it – criteria

The starting point is to know what the system is for and what criteria need to be met:

-Maximum smoke layer temperature

-Minimum clear layer height

-Maximum air inlet velocity.

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How to use it – design fire

This is the most critical part of the design:

-Pre flashover, not maximum possible size

-Realistic maximum before control by sprinklers or fire fighters

-Realistic high and low heat outputs.

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How to use it – smoke reservoirs

Design formulae in the TR do not allow for cooling of the smoke layer. Therefore: -Maximum reservoir areas are limited to keep cooling low enough to be ignored, or; -Heat losses by conduction and radiation should be separately calculated. The 60m limit separately limits travel distance for evacuation under the smoke layer.

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Interaction with sprinklers

Sprinklers allow use of a smaller design fire. The heat output per m2 is unchanged. Cooling of the smoke layer due to sprinklers is explicitly included in the calculations. Guidance on initiation gives priority to sprinklers unless the SHEVS is a life safety system.

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Options

The standard is deliberately written with all calculations in Informative Annexes.

This allows use of alternative calculation methods, such as NFPA 92 or 204, while still following 12101-5.

Mixing calculation methods is not recommended. Follow one method throughout.

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Results

Following this standard provides design flow rates and ventilation areas.

There is still much work to be done to turn this into an installed system.

CEN/TR 12101-4 and/or national guidance can be used for this.

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The future

12101-12 for time dependent design is being written.

It takes a more “European” approach.

12101-5 will need to change to match it – but probably not for at least 5 years.

In the meantime – used properly – CEN/TR 12101-5 is a good guide, probably the best.

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The end

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