Limiting Oxygen Index Instrument

The FTT Oxygen Index (OI) and Temperature Oxygen Index (TOI), which replace the Stanton Redcroft FTA and HFTA, offer many improvements.

The latest oxygen analyser technology for high accuracy, reliability and long operating life.

Determination of Flammability

The Oxygen Index measures the minimum percentage of oxygen in a test atmosphere that is required to marginally support combustion. The OI is an economical and precise quality control test of combustible materials. Its ease of use together with high levels of precision has made this technique a primary characterising and quality control tool to the plastic and electric cable industries and it has been specified by several military and transport groups.

The FTT apparatus enables the oxygen index to be determined in accordance with ASTM D2863, ISO 4589 Part 2 or the UK Naval Engineering Standard NES 714.


  • New Paramagnetic Oxygen Cell to assess accurate oxygen (< 0.1%) levels
  • Compact unit used inside a laboratory hood, with ventilation
  • Automatic flow control gives oxygen level adjustment by turning one single valve
  • Quick loading of test specimen into test chimney measuring 450 mm × 75 mm
  • Digital display of temperature of gas mixture entering the test chimney
  • Digital display of oxygen percentage in atmosphere during test (no calculations needed)
  • Sample holders for both rigid and flexible samples supplied
  • Shortened gas path for rapid response

The Elevated Temperature Oxygen Index is used alongside the OI to determine the oxygen index at temperatures up to 125°C. Research shows that the elevated temperature at which the materials will burn in air is a better determinant of combustibility than is the conventional oxygen index. Oxygen Index values fall when the gas temperatures are increased.

Elevated test temperatures are set by adjustment of the preheated gas temperature levels and setting the heated glass furnace wall temperature. The temperatures of both heated sections are continuously displayed on the TOI control unit. When experiments are being carried out using different oxygen levels, gas conservation is achieved by using air from an integral quiet running pump between tests. Bottled nitrogen and oxygen supplies are only switched into the system for testing.
The FTT apparatus enables the oxygen index at elevated temperature to be determined in accordance with ISO 4589 Part 3 or the UK Naval Engineering Standard NES 715.


  • Test temperature to 400°C
  • Digital display of sample temperature
  • Digital display of column and preheater temperatures
  • Transparent radiant heated test column
  • Highly efficient gas preheater
  • Air pump to conserve oxygen and nitrogen supply during standby period
  • Propane ignition source

The FTT OI and TOI have been designed to be compact for efficient use in a standard fume cupboard (or under a simple ventilation hood that can be supplied if required). The instruments give continuous digital readout of oxygen concentration in the test atmosphere to facilitate quick settings of test concentration. Stabilised oxygen percentages are automatically read from the digital readout and no additional flow adjustments are required.

This is a considerable improvement over systems that use analogue gauges or require flow matching and the use of graphs or tables to calculate oxygen concentration.

We are the only authorized Fire Testing Technology Agent in North America