LOI – ISO 4589

What Is LOI — ISO 4589?

The limiting oxygen index test is performed in which the sample in a vertical position is ignited in an oxygen-nitrogen mixture; It is the experiment in which the lowest oxygen volume percentage required for combustion to continue is determined.

Purpose of LOI — ISO 4589

The purpose is to express the material's tendency to continue burning with a comparative number.

Which Products Is LOI — ISO 4589 Applied To?

Plastic and composite materials
Cable insulation and sheaths
Textiles and fibers
Flame retardant formulation development

In Which Sectors Is LOI — ISO 4589 Used?

ConstructionConstructionDemiryoluElectricalConsumer Products

Standards Related to LOI — ISO 4589

ISO 4589combustion behavior with oxygen index test

LOI — ISO 4589 Conditions

Gas mixture: Oxygen and nitrogen; The threshold is sought by gradually changing the concentration
Specimen: Vertical bar or film with standard defined dimensions
Ignition: Flame application at a time and position defined in the standard
criterion: Burning continues for a defined time or length

Equipment for LOI — ISO 4589

LOI test column and gas mixing system
Calibrated flowmeters or oxygen analyzer
Sample holder and ignition burner
Specimen-preparation bench

Sample Requirements for LOI — ISO 4589

Sample dimensions and surface must comply with the standard
The sample must be conditioned and dry
Gas mixture concentration must be verified
Threshold search must be carried out using the method defined in the standard.

Duration of LOI — ISO 4589

Typically 3–6 days.

LOI — ISO 4589 Procedure

1Samples are prepared and conditioned.
2The gas mixture is adjusted and the concentration is verified.
3The sample is ignited and burning is monitored.
4The threshold is sought by changing the concentration gradually.
5LOI value is calculated by the method defined in the standard.
6The result is reported.

LOI — ISO 4589 Acceptance Criteria

The acceptance criterion is the minimum LOI value given in the specification.

Evaluation of Results

LOI is not a fire safety classification; It is a comparative index measured under laboratory conditions. A high LOI value does not guarantee good actual fire behavior and is not a substitute for response to fire classification.

LOI — ISO 4589 Report

Standard applied
Sample size and conditioning
Gas mixture and verification
LOI value
Assessment

Accreditation

EUROLAB holds internationally recognised accreditation obtained from accreditation bodies party to the IAF and ILAC multilateral recognition arrangements, under ISO/IEC 17025 for laboratory testing, ISO/IEC 17020 for inspection and surveillance, and ISO/IEC 17021-1 and ISO/IEC 17065 for system and product certification. This chain ensures the reports and certificates issued are accepted worldwide.

Whether this test can be offered within accredited scope depends on your product and the standard applied; since accreditation is method-based, the scope is confirmed in writing at the quotation stage.

Scope and authorisations

Related Regulations

Material and product specifications

Fire Testing — What Does This Testing Field Cover?

The section below describes the field that the LOI test belongs to; the conditions and acceptance criteria of this particular test are given in the sections above. The scope specific to your product is confirmed in writing at the quotation stage.

Fire testing measures two different concepts, and confusing them is the most common mistake in the field. REACTION to fire describes how much a material contributes to the start and growth of a fire. RESISTANCE to fire is the ability of a building element to hold a fire back for a defined period. One is a material property, the other a property of an element.

On the reaction side, ignitability, flame spread, heat release, smoke production, flaming droplets and toxic gas release are measured. The result is translated into an EN 13501-1 class in Europe, ASTM E84 indices in North America and a UL 94 class for appliance plastics. These three systems cannot be converted into one another; their scales and set-ups differ.

On the resistance side, furnace tests are carried out. The element is exposed to a defined temperature-time curve and it is measured how long it maintains three functions: load bearing (R), integrity (E) and insulation (I). For a fire door, the designation EI 60 says the element maintains its integrity and insulating function for sixty minutes.

SCALE is decisive in this family and directly affects cost. Small flame tests are suitable for screening materials and are fast and inexpensive. But real fire behaviour changes with scale: a material that self-extinguishes on a small specimen may sustain a flame over a large surface. Large-scale set-ups such as the room corner test and full-scale facade tests are therefore indispensable in critical applications.

Facade systems have become the most sensitive subject in the field in recent years. The rapid spread of facade fires in tall buildings has led national regulations to require large-scale facade testing. What is assessed here is not a single material but the SYSTEM: insulation, cladding, air cavity, fixings and fire barriers are tested together.

Smoke and toxicity form a separate body of work, because most deaths in a fire are caused by smoke rather than flame. In rail systems and on ships, smoke density and gas toxicity measurements are mandatory items; in an enclosed space the time available for evacuation depends on these values.

Cables have a sub-body of their own. A cable bundle inside a building can form a serious path for fire to spread between floors; flame spread, smoke production, halogen content and circuit integrity are therefore assessed for cables under separate standards, and in Europe the EN 13501-6 classification is used.

Method groups in this field

Non-combustibility and calorific value
The EN ISO 1182 non-combustibility furnace and EN ISO 1716 gross calorific value; the determinants of classes A1 and A2.
Single burning item (SBI)
EN 13823; heat release, flame spread and smoke production are measured together in a medium-scale corner set-up.
Small flame
Ignitability with a single flame source to EN ISO 11925-2; UL 94 horizontal and vertical burning; needle flame and glow wire.
Cone calorimeter
ISO 5660 / ASTM E1354; heat release rate, total heat release and smoke production are measured. The most informative test in material development.
Fire resistance
Furnace tests with the standard temperature-time curve; separate set-ups for doors, walls, floors, glazing and service penetrations.
Large scale
Room corner test (ISO 9705, NFPA 286), facade fire tests and vertical flame spread tests on cable bundles.
Smoke and toxicity
Optical smoke density, smoke gas analysis and toxicity indices; mandatory in rail systems and marine.

Commonly confused in this field

Reaction to fire and resistance to fire are different concepts; the specification must be explicit about which is required.
UL 94, ASTM E84 and EN 13501-1 results cannot be converted into one another.
A small-scale result is not evidence of large-scale behaviour; large-scale testing is required in critical applications.
A class is valid together with the end-use installation of the product; a different substrate or air cavity changes the result.
For facade systems a result for a single material is not sufficient; the system must be tested as a whole.
The fire class of a product does not show the fire resistance of an assembly made from it.

Which decisions these results support

The fire class in the declaration of performance for construction products
Regulatory compliance in the selection of cables, flooring and interior linings
Approval of interior materials for rail vehicles, ships and aircraft
Approval of the facade system design
Meeting insurance and project specification requirements

Related Tests

Frequently Asked Questions About LOI — ISO 4589

Does a high LOI value indicate that the material is fire safe?

It doesn't show. LOI is an index that measures whether combustion continues only in a vertical position and in a controlled oxygen environment. Fire reaction and heat release tests are required for fire safety.