Oxygen Index

Limiting Oxygen Index Instrument

The Oxygen Index is the most economical and precise quality control test of combustible materials. Notably, it’s ease of use, along with high levels of precision, make this instrument a primary tool to the plastic and electric cable industries. (Specified by several military and transport groups) Also, the LOI measures the minimum percentage of oxygen in the test atmosphere that is required to marginally support combustion.

Why this Oxygen Index Instrument

The FTT Limiting Oxygen Index instrument is designed to be compact for efficient use in a standard fume cupboard. Moreover, it gives continuous digital readout of oxygen concentrations to improve quick settings of test concentration. Additionally, stabilized oxygen percentages are read from the digital readout. Therefore, no additional flow adjustments are required. This is a huge improvement over systems that use analogue gauges. Or systems that require flow matching and the use of graphs or tables to calculate oxygen concentrations. All of these features make the LOI instrument as automatic as currently possible.

It can be used with the Elevated Temperature Oxygen Index apparatus to determine the oxygen index at temperatures up to 125°C.


  • 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

We are the only authorized company in North America to sell equipment and service from Fire Testing Technology