Limiting oxygen index tester is a new equpiment developed according to the technical requirements stipulated in the national standard of ISO 4589 “Textiles — Burning Behaviour — Oxygen Index Method” and GB/T2406-1993 “Plastics — Determination of Flammability by Oxygen Index”. LOI tester used to measure the combustion properties of various textiles including woven, knitted, non-woven fabrics, etc. It can also be used to measure the combustion properties of plastics, rubber, paper, etc. Limiting oxygen index apparatus can be used as a means to identify the flame retardancy of polymers, and it can also be used as a research tool-laboratory research on flame retardant formulations, etc.
The LOI tester is an instrument manufactured according to the technical conditions specified in the national standard ISO 4589 “Plastics — Determinatioin of Flammability by Oxygen Index”. Oxygen index apparatus used to determine the oxygen concentration (volume percent) required by the polymer during combustion. The oxygen index value of a polymer is the minimum volume percentage of oxygen in the oxygen-nitrogen gas mixture required to keep the substance burning for 50 mm or 3 minutes after ignition.
Combustion Cylinder Material
High-Temperature Heat-Resistant Glass
Inner Diameter of
Combustion Cylinder: Φ75mm｜Φ100mm
Height of Combustion
Cylinder: 450mm ~ 500mm
Gas Flow Rate
(40±2) mm/s lnside the Combustion Tube
Response Time: ＜200ms
Stable Time: ＜5s
Gas Source Requirment
Nitrogen and Oxygen for Industrial Use (Purity>99%)
0.2 ~ 0.3Mpa
0.05 ~ 0.15Mpa
± 0.1 %
0~10 L/min（60~600 L/Hour）
RT~ 40℃, RH 45%—75%
220V, 50Hz, 1 Phase
W420mm x D350mm x H560mm
Limiting oxygen index test apparatus measures the minimum concentration of oxygen required for a sample to burn. Oxygen index is an important reference value to measure the flame retardant properties of materials. Oxygen index means that a certain size of material (test piece) is loaded into the test device, and under specified conditions, a mixture of oxygen and nitrogen is introduced, the test piece is ignited with an igniter, and the minimum oxygen concentration necessary to maintain continuous combustion is determined (expressed as a percentage).
The limiting oxygen index (LOI) is widely used as a measure of flammability. Because, in its standardized form, the test is precise and produces quantitative results as opposed to the qualitative (pass/fail) results obtained in other small flame tests. The LOI is the minimum oxygen concentration in a flowing atmosphere that will sustain downward burning of a plastic strip or fabric. As such, the LOI involves the coupling of condensed and gas phase processes of flaming combustion at or near extinction, and for this reason, has defied simple description. Consequently, it is not clear what the LOI test measures, although polymers that exhibitchanring, low heat of combustion, thermal stability and flame poisoning by halogens tend to achieve high LOI values in the test.
Automatically realize closed epoxy concentration control, and accurately control the oxygen concentration value in the combustion barrel. The designed of limiting oxygen index chamber can ensure that the gas is fully mixed in a short time, and the data is more accurate.
One-piece structure, industrial design appearance, beautiful and easy to operate. Oxygen index test apparatus equipped with 2 mass flow controllers (MFC) to control the mixing ratio of nitrogen and oxygen, precise and convenient control.
Equipped with a gas diffusion ring, mixed with glass beads to make the outlet gas more uniform. Limiting Oxygen Index apparatus (LOI) equipped with high temperature resistant quartz glass cylinder, the independently designed end cover is convenient for cleaning the glass cylinder.
Equipped with a paramagnetic oxygen concentration sensor, the display oxygen concentration accuracy is ±0.1%. Compared with the traditional electrochemical oxygen sensor, there is no service life limit (the electrochemical oxygen sensor needs to replace the oxygen battery frequently), with higher accuracy and faster response time.
Oxygen index apparatus equipped with stainless steel supportable and unsupported specimen grips for easy switching. Portable igniter with precision needle valve to adjust flame size. Programmable logic controller (PLC) + touch screen control, digital setting of nitrogen and oxygen concentration, no need for repeated manual adjustment.
Despite the fact that one or more of these characteristicsis generally regarded as being indicative of low flammability, There is almost no correlation between the LOI of a material and its performance in other fire and flame tests. In this paper we investigate how material and fire properties contribute to the outcome of the LOI test by measuring the heat release rate in the test and applying steady burning and flame spread criteria to explain the results. → Page Source: https://www.researchgate.net/publication/288308898_The_limiting_oxygen_index_test_revisited
Open the valve of the gas supply part, and arbitrarily select the mixed gas concentration, the flow rate is about 10L/min, close the outlet and inlet valves, and record the pressure and flow of oxygen, nitrogen, and mixed gas.
Preparation and Inspection Before the Test
Leave it for 30 minutes, and then observe the values displayed by each pressure gauge and flowmeter, and check with the previous recorded values. If there is no change, it means that the device has no air leakage.
Supplementary Note: The temperature and humidity test is carried out in the atmosphere with a temperature of 10 to 40°C and a relative humidity of 45% to 75%.
Place the LOI tester on a work platform (preferably in a fume hood) and fix it steadily. Connect the O2 and N2 ports on the back of the instrument to the corresponding O2 and N2 cylinder ports with the connecting pipe and air source connector parts attached to the instrument; connect one end of the randomly configured nylon pipe to the base of the combustion cylinder, and the other end to the instrument N2+O2 interface on the back.
Installation of Limiting Oxygen Index Tester
Screw the support rod of the sample holder into the combustion seat, put a metal piece, and then put the glass beads that come with it, then put a metal piece and install the sample holder on the sample holder, and insert the glass tube into the burner cylinder.
The sample is clamped on the sample clamp and is perpendicular to the combustion cylinder. In the upward flow of oxygen and nitrogen, the upper end of the sample is ignited, the combustion characteristics are observed, and the after-burning time or damage length is compared with the specified limit value.
Oxygen Index Method and Notification
Through the test of a series of samples in different oxygen concentrations, the minimum oxygen concentration value expressed by the percentage of oxygen during combustion can be measured. The test sample should have 40% to 60% exceeding the specified afterburning and smoldering. time or damage length.