The limiting oxygen concentration (LOC) is the experimentally determined oxygen concentration which will just not allow an explosion of a dust/air/inert gas mixture. It is a compound and inert gas specific characteristic.

The possibility of dust explosions in process equipment can in principle be effectively eliminated by substituting the air by gas which makes flame propagation in the dust cloud impossible. Since the use of large quantities of inert gas in a plant can be expensive, it is important to limit the inert gas consumption to the extent possible. For most dusts it is not necessary to substitute the entire atmosphere in the actual area by e.g. nitrogen to obtain inerting. Hence it is essential to know the critical gas composition for inerting the dust in question. In some cases it may even be of interest to use smaller fractions of inert gas than required for complete inerting, because this will reduce both the ignition sensitivity of the dust cloud, and the maximum pressure and rate of pressure rise at constant volume.

• EN 14034: Determination of explosion characteristics of dust clouds: Part 4: Determination of the limiting oxygen concentration LOC of dust clouds
• VDI-Richtlinien 2263, Blatt 1: Untersuchungsmethoden zur Ermittlung von sicherheitstechnischen Kenngrössen von Stäuben (1990)
• Kühner AG, Operating instructions for the 20 litre apparatus
• W. Bartknecht, Staub Explosionen: Ablauf und Schutzmassnahmen (1987)
• R.K. Eckhoff, Dust explosions in the process industries (1997)
• Handboek explosiebeveiliging, Kluwer-Editorial