design fires for smoke control dr. john h. klote pe fire and smoke consulting...

Design Fires for Smoke Control

Dr. John H. Klote PEFire and Smoke Consulting

john@SmokeControlExpert.com

www.SmokeControlExpert.com

Learning Objectives• Provide an understanding of fire

growth, flashover, fully developed fire and fire decay.

• Provide an overview of the basic concepts of developing design fires for smoke control systems.

• Extensive Treatment of All Aspects of Smoke Control

• For more information about design fires, see Chapter 5 “Fire Physics & Design Fires”

Design Fires

• Used for Atrium Smoke Control and Tenability Systems

• IBC– No Prescribed Design Fires– Requires Analysis of Design Fires

• Many Engineers – New to Design Fires

• This Talk: – Overview of Analysis of Design Fires– Focus on Highlights

UK Information on Design Fires

• Industrial & Warehouse (not high racked) -1990 Smoke Ventilation Association Guide:– Sprinklered Steady Fires - 3m x 3m to 9m x 9m.– Unsprinkleres Steady Fires – 2 Times as Big

• Steady Fires in Car Parks – BS 7346-7• Guidance for Offices & Hotels – BS 7346-4 and

5 and in BR368• General Information on Specific Objects:

– BS 7974 (UK fire engineering standard) – BRE design fires database CD

Design Fires

• Normally Most Important Property - Heat Release Rate (HRR)

• Other Properties (toxic gases, reduced visibility, etc.) - Tenability Systems

• For simplicity - Only Discuss HRR

• HRR of a Design Fire:– Steady – Unsteady

• Steady HRR – Peak of Unsteady HRR

Fully Developed Fire

• Called “Ventilation Controlled Fire”• Room with One Opening

– HRR Controlled by Opening Size – HRR Equation

1/ 21260 w wQ A H

where Q = HRR (kW) Aw = area of opening (m2), Hw = height of opening (m).

HRR Measurement

• Oxygen Consumption Calorimeters– HRR per unit O2 Consumed – Almost

Constant (13.1 MJ per kg of oxygen + 6%)– Open Air Calorimeter – Room Calorimeter

Design Fires

• Normal Fuels - Objects Planned for Space• Transient Fuels - In a Space Temporarily

– Examples: Trash, Stacked Wood Pallets, Furniture After Delivery, etc.

• Atrium Fires– Normal & Transient Fuels– No Benefit of Sprinklers (Ceilings > 35 – 45 ft)– Transient Fuels: Suggest Min. 2000 Btu/s

• Non-Atrium Fires– Normal & Transient Fuels– Fires w/ Axisymmetric Plume – CFAST– Shielded Fires (NIST & NRCC Models)

Questions?

Dr. John H. Klote PEjohn@SmokeControlExpert.com

www.SmokeControlExpert.com