Views: 84521 Author: Site Editor Publish Time: 2026-11-11 Origin: Site
A buyer requests flame retardant polyester DTY with LOI ≥32. Another supplier offers a yarn described as "high flame retardant" without specifying any test results.
Are the two products technically comparable?
To answer that question, it is useful to understand what the Limiting Oxygen Index measures, what the number 32 represents and what additional information a textile manufacturer should request.
LOI stands for Limiting Oxygen Index, also known as oxygen index (OI).
It describes the minimum oxygen concentration in a controlled oxygen-and-nitrogen atmosphere that supports combustion of a test specimen under defined laboratory conditions.
The result is commonly expressed as a percentage.
For example, an oxygen index of 32 means that the material exhibited the specified combustion behavior at an oxygen concentration of approximately 32% in the relevant laboratory test.
Normal atmospheric air contains approximately 21% oxygen.
A material with a higher oxygen index generally requires a more oxygen-rich environment to support combustion under the specified test conditions.
This makes LOI a useful indicator when comparing materials tested using compatible procedures.
In a typical oxygen index test, a prepared specimen is positioned inside a controlled testing apparatus.
A mixture of oxygen and nitrogen flows through the apparatus, and the specimen is exposed to a defined ignition procedure.
The oxygen concentration is adjusted according to the testing method until the required combustion criterion is reached.
The result depends on both the material and the conditions of the test.
An important reference is ISO 4589-2, which specifies an ambient-temperature oxygen index method for suitable plastics specimens.
For textile fibers and fabrics, the buyer should verify that the laboratory has selected an appropriate method and specimen preparation procedure. A plastic specimen test and a textile fabric test should not automatically be treated as equivalent.
An LOI of 32 indicates a substantially higher oxygen requirement for sustained combustion under the relevant test conditions than the oxygen concentration found in normal air.
For buyers comparing different flame-retardant polyester formulations, this can be a meaningful technical characteristic.
However, it would be incorrect to say that any polyester yarn with LOI 32 is completely fireproof.
LOI does not directly establish every aspect of fire performance, including:
Flame propagation in a finished curtain
Ignition behavior of a complete upholstery assembly
Heat release under a different fire scenario
Smoke production and toxicity
Flaming droplets or molten material behavior
Performance after a prescribed cleaning cycle
Each of these may require a different test method or evaluation.
Imagine two polyester filament yarns with similar reported oxygen index values.
One is an FR DTY 150D/48F yarn. The other is an FR FDY yarn of a different denier and filament construction.
The materials may share a comparable oxygen index, but they do not necessarily produce identical fabrics.
Yarn texture, density, weaving structure and surface area can influence how the final fabric behaves when exposed to ignition.
Additional finishing operations may also introduce other materials into the textile structure.
For this reason, yarn-level LOI should be treated as part of a technical specification rather than a finished fabric performance guarantee.
A common source of confusion is the relationship between LOI and product-specific fire testing.
Test or Standard | Primary Purpose |
|---|---|
Oxygen Index / LOI | Assess oxygen concentration required to support specified combustion |
NFPA 701 | Assess flame propagation of textiles and films |
EN 13773 | Classify burning behavior of curtains and drapes |
EN 1021-1 / EN 1021-2 | Assess ignition resistance of upholstered furniture assemblies under specified ignition sources |
These tests answer different questions.
A yarn manufacturer may provide an oxygen index report for its polyester material, while a curtain manufacturer may need to obtain an NFPA 701 or EN 13773 test result for a specific finished fabric.
One result cannot simply replace the other.
Before accepting a supplier's LOI claim, request enough information to identify the tested material and understand the test conditions.
A useful report should show:
Testing laboratory and report number
Applicable test standard and version
Description and identification of the tested specimen
Sample preparation and conditioning, where relevant
Reported oxygen index result
Testing date
Any relevant limitations or observations
The sample identification is particularly important.
An LOI report obtained for one raw-white yarn grade should not be assumed to cover every denier, black dope-dyed variation or modified production formulation.
NEXTILE supplies selected flame-retardant polyester filament yarn grades for textile manufacturers.
For projects requiring FR DTY with LOI ≥32, buyers should provide the intended yarn specification and test requirements so that suitable production options and available technical documentation can be evaluated.
Typical purchasing information includes yarn type, denier, filament count, intermingling, color, quantity and destination port.
Where finished fabric certification is required, the fabric manufacturer should arrange testing of its actual fabric construction using the applicable standard.
Contact NEXTILE to discuss FR Polyester DTY, available LOI information and export quotations.
No. It indicates the oxygen index result under a specific laboratory procedure. Actual fire behavior can differ with ignition conditions and product construction.
Results should be compared only after checking the test method, specimen preparation and relevant conditions. Different procedures can produce results that are not directly equivalent.
No. NFPA 701 evaluates flame propagation in specified textiles and films, while LOI measures a different property.
Not necessarily. Colorants, formulations and processing conditions can affect measured performance. Relevant product grades should be verified separately when necessary.
