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BS476 Class 0&1 Explained What Is Class 1?: Answer

Class 1 refers to a fire rating classification defined by BS476 Part 7 that measures the distance and speed at which flames will spread across a surface. A good Class 1 result would be flames spreading less than 165mm over 10 minutes. Class 0 is a higher classification from building regulations that requires a surface to achieve a Class 1 rating as well as meet strict heat emission thresholds in the BS476 Part 6 fire propagation test to limit heat released during a fire. Class 0 provides protection from flame spread and limits the amount of heat released from a surface. The required class will depend on the regulations or specifications for a particular building project.

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580 views1 page

BS476 Class 0&1 Explained What Is Class 1?: Answer

Class 1 refers to a fire rating classification defined by BS476 Part 7 that measures the distance and speed at which flames will spread across a surface. A good Class 1 result would be flames spreading less than 165mm over 10 minutes. Class 0 is a higher classification from building regulations that requires a surface to achieve a Class 1 rating as well as meet strict heat emission thresholds in the BS476 Part 6 fire propagation test to limit heat released during a fire. Class 0 provides protection from flame spread and limits the amount of heat released from a surface. The required class will depend on the regulations or specifications for a particular building project.

Uploaded by

Chin Chloe
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as PDF, TXT or read online on Scribd
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Eco-Sol Ltd www.fireproofspray.co.

uk

BS476 Class 0&1 Explained

Question: What is Class 1?


Answer: Class 1 is a classification defined by BS476 Pt 7 – Surface spread of


Flame. The

test measures the distance and time a flame will spread across a surface.

Results range from:

The worst, Class 4 – i.e. longest distance and fastest of flame spread, To the best,
Class 1 – i.e. least distance and slowest of flame spread.

e.g. A good Class 1 result would be the flame not spreading further than 165mm
from the point of ignition over the total test time of 10 minutes.

Question: What is Class 0?



Answer: Class 0 is not a fire test but in fact a classification from The Building
Regulations

1991 – Fire Safety, Approved Document B.



In order for a system to achieve a Class 0 rating it must meet the following
requirements:

Achieve a Class 1 fire rating from BS476 Pt 7 – Surface spread of Flame

*Achieve an index of I = less than 12 and i1 = less than 6 from BS476 Pt 6 – Fire
Propagation.

*This Fire Propagation test measures the amount of heat the surface is giving off
during the fire. Measurements are taken frequently throughout the 20 minute test
and then calculated using a special formula to achieve an ‘index rating’.

For the surface to achieve Class 0 classification the index figure that is produced
after 90 seconds must be 6 or less and after the full 20 minutes must be 12 or less.
The index ratings do not equate to exact temperatures but are within the specified
guidelines.

To Summarise:

Class 1 – Protects your surface from the spread of flames.



Class 0 – Protects your surface from the spread of flames AND limits the amount of
heat released from the surface during a fire.

The decision whether to meet Class 1 or Class 0 classification is usually


determined by your Building Regulations Officer or Architect.

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