Protecting property, saving lives

Mark Cummings,head of section: fire testing at Chiltern International Fire discusses the testing of fire doors and the role of third-party certification.

BUILDING OWNERS and developers are often faced with a legal requirement for products such as doors, screens, partitions and ceilings to resist the passage of fire and so control the spread of fire. They have a duty to protect life, by enabling occupants to escape and allowing the fire & rescue services to gain access to fight the fire. The location and period of fire resistance required for construction products is determined by legislation, codes of practice or the accepting authority.

Fire resistance is proven through destructive fire testing and by assessment. Manufacturers or designers submit their products to a United Kingdom Accreditation Service (UKAS)-accredited test facility, such as Chiltern International Fire (CIF). Third-party certification goes beyond testing, in that it demonstrates consistency of manufacture which, in combination with test evidence, provides the confidence that every product will perform as expected.

A number of test standards are used to show the performance of a product or construction under a generalised fire situation. Most common in the UK are the British Standard 476: Part 20 series, but increasingly nowadays manufacturers may also test to European Standards (BS ENs) for different types of building element, for example:

• Doors and partitions BS 476: Part 22 / BS EN 1634-1
• Load bearing walls BS 476: Part 21 / BSEN 1365-1
• Non-load bearing walls, partitions and glazed screens BS 476: Part 22/BSEN 13641
• Loaded floors BS 476: Part 21 / BS EN 1365-2
• Ceilings BS EN 1364-2

The tests are designed to simulate the product’s intended end-use, eg doors are built into an appropriate supporting construction.

The specimen and any relevant supporting construction are built into a 3m x 3m restraint frame, which is mounted on the front of a furnace. The temperature within the furnace is controlled according to a prescribed and internationally accepted time/temperature regime. The time/temperature and pressure regime within the standard is intended to represent a post flashover condition - flashover being the point at which all objects in the fire compartment have ignited.

In a real fire, the time period to flashover can be extremely long or extremely short, depending on a range of variables, such as the nature of the fire load, compartment size and shape and ventilation. Given the unknown time to flashover, testing therefore represents the fire scenario from the point of flashover and does not consider the period of fire growth.

Products will be required to withstand fire for a certain duration – eg 30, 60, 90 or 120 minutes, so the test will run for this period or until the specimen fails and it is no
longer safe to continue. Failure relates to integrity, insulation and radiation and is determined by the criteria set out in the table below.

The testing process is relatively straightforward. It is simply a matter of submitting a specimen for a testing laboratory like Chiltern Fire to install and test within a suitable
structural surround. However, for a manufacturer to determine what size and configuration of product to test, it is a little more complicated.

There are many options to be considered to cover final market requirements, eg different types of hardware, different glazing options and so on. At Chiltern Fire, we will assist the designer from the very beginning to ensure that what is tested will cover as many of the end requirements as possible.

Following the test, a report will be issued that will contain all the construction details of the tested specimen, together with information on the size and configuration of the test sample. The test report itself is a purely factual document, stating
the results, but it will include other relevant information such as observations taken by the test engineers, graphs showing furnace and specimen temperatures and distortions (if applicable). Test reports only relate to what has been tested and do not cover design variations.

If the manufacturer wishes to make any changes to a construction tested under British or European standards, this will require either another fire test or an assessment: a desktop study undertaken by an experienced fire consultant. The assessment will allow variations to a tested design, although the nature and scope of any variations will largely depend on the size and configuration of the test specimen.

It is important, therefore, that before any testing is carried out, the client has a full and frank discussion with the testing laboratory, to establish the precise requirements for the complete product range intended for the market. The laboratory will advise whether a single test is appropriate, or whether a series of tests will be required to meet the intended enduse applications.

Once the test programme has been completed (and all results are successful), the laboratory will be able to produce a Global Assessment (GA) report, bringing together all the test data into a single document. The GA report becomes the document upon which the client will trade, as it will clearly explain the full scope of the product. Global Assessments can bring together the results of multiple tests and provide a scope based on all of the evidence.

Project specific assessments can also be produced, tailored to the specific needs of a building project.

Assessments cover various aspects of design including:
1. How to adjust the leaf dimensions and whether leaf size adjustment is appropriate.
2. The use of overpanels and how to install them.
3. Acceptable increases in leaf dimensions (height and width).
4. Acceptable changes in doorset configurations (single leaf, double leaf, single acting, double
acting).
5. The use of and installation of glazed apertures.
6. The option to use various glass types.
7. Door frame variations if appropriate.
8. Smoke control requirements

Third-Party Certification
Once all the evidence is in place and any assessment report has been prepared, we
would recommend the product is manufactured under a quality management system audited by a third-party, such as the QMark scheme for fire door manufacture offered by Chiltern Fire’s sister company BM TRADA Certification, which insists on audit tests on the product and verification of factory production control procedures. This type of scheme will ensure that:

1. The quality of the product, when sold to an end-user, is of a similar quality to that
tested, and
2. The product should be expected to achieve the minimum stated fire resistance period that has been tested and claimed.

The complete manufacturing process must be quality controlled to the relevant ISO standard (or similar system), with the process audited yearly to ensure that areas such as calibration of equipment, handling of materials, stock control and documentation are all controlled and meet prescribed standards. Further audit testing of the product is also required as a part of this type of accreditation scheme,
usually every three years, which will physically highlight any weak areas in the manufacturing process.

Training, in our view, is extremely important. Fire doors are an engineered product and as such must be designed, manufactured and installed correctly. It can be the
simplest design and detailing issues which make the difference between pass and
fail. Chiltern International Fire includes a full-scale fire test as part of our training courses, as the visual impact of a door tested to destruction is dramatic and the lessons learned stick in the mind.

FIRE TESTING: FAILURE CRITERIA

Continuous flaming integrity: Simply the fact that sustained flaming (more than 10 seconds) has occurred on the nonfire side.

Cotton pad integrity: Shows that gases passing through the specimen are sufficiently hot to ignite combustible material on the non-fire side and therefore spread the fire. A cotton pad is employed by mounting the pad against the specimen on any glowing areas visible on the exposed face.

Gap gauges 6mm or 25mm integrity: Measures the width of gaps in the specimen and evaluate the rate of specimen deterioration which must remain below prescribed levels

Insulation: Measured by attaching thermocouples to the unexposed face at positions stated in the relevant testing standards. The individual thermocouples are logged throughout the test to determine an insulation failure. The insulation failures occur when either an individual thermocouple on the sample reaches 180°C above laboratory ambient conditions or 140°C above laboratory conditions as an average group of thermocouples.

Radiation (total heat flux): Measured for non-insulating samples using a heat flux radiometer positioned central to the sample and 1m away. The levels are measured in kw/mÇ and the sample is deemed to have failed once 15kw/mÇ is reached.