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Oxygen Index BS 2782:141 & ISO 4589-2

MANUFACTURER Fire Testing Technology (manufacturer's website)
AVAILABILITY Official workshop hours are: 9:30 to 12.30 and 13.30 to 16:30 (in practice technicians are often available outside of these times)
RESTRICTIONS Use of this equipment requires evidence of advanced scientific standing & expertise, allied to proof of competency both in management of the health & safety environment & adherence to fundamental ethical principles relating to research & consultancy.
CONTACT 1 External enquiries: Martine Townsend - Grants & Funding Unit
CONTACT 2 Internal enquiries: Dr. Anna A. Stec
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SITE Harris Site


Oxygen Index BS 2782:141 & ISO 4589-2

This is a widely used, but frequently misinterpreted test which provides a single figure related to ignitability.

Limiting Oxygen Index (LOI) is the per cent concentration of oxygen at which a small specimen will only just burn downwards in a candle like manner. The test is probably the most well-known of the standard fire tests. The apparatus holds a small specimen of material which is clamped vertically in a tube in an atmosphere where the relative concentration of oxygen and nitrogen can be changed. The aim is to test the flammability of the sample with a small pilot flame to find the minimum oxygen concentration required to just sustain combustion of the sample.

The test result is on a numerical scale which simplifies comparison of materials. It is very repeatable and is used for quality assurance and to indicate the potential flammability of a material. However it is essentially a small flame test and while a high index is indicative of a less easily ignited and less flammable material, materials with high limiting oxygen index (LOI) values (i.e. greater than 21) undergo flaming combustion at oxygen concentrations below 5%, in a fully developed, real fire. This is one of the very few test apparatus where steady burning conditions can be replicated on a small scale.

Item ID #769.

Last Updated: 9th August, 2017