LOI refers to the mass loss of a combustion residue whenever it is heated in an air or oxygen atmosphere to high temperatures. In the cement industry, use of the term LOI normally refers to a mass loss in a sample heated to 950°C. To combustion engineers, the term LOI normally refers to mass losses in samples heated to temperatures normally less than 950°C. These test methods establish a procedure for determining LOI values for combustion residues heated to 750°C or 950°C. LOI values from these test methods can be used by industries that utilize combustion residues in various processes and products.

If the solid combustion residue is heated to estimate the combustible or unburned carbon in the sample, it has been shown that LOI and estimation of unburned carbon do not necessarily agree well with each other and that LOI should not be used as an estimate of unburned carbon in all combustion residues. . Direct determination of unburned (combustible) carbon can be carried out using Test Method D6316.

If the solid combustion residue is heated to prepare an ash for the determination of the concentrations of major and minor elements, use the heating procedure described in Test Methods D3682, D4326, and D6349, or the procedures for the 750°C LOI determination described in these test methods (Method A).

If the solid combustion residue is heated to prepare an ash for the determination of the concentrations of trace elements, use the heating procedure described in Test Methods D3683 and D6357.

Note 1—Combustion residues produced in furnace operations or other combustion systems can differ from the ash yield, as determined in Test Methods D3174 and D5142, because combustion conditions influence the chemistry and amount of ash. Combustion causes an expulsion of all water, the loss of carbon dioxide from carbonates, the conversion of metal sulfides into metal oxides, metal sulfates and sulfur oxides, and other chemical reactions. Likewise, the “ash” obtained after igniting combustion residues can differ in composition and amount from Test Methods D3174 and D5142 ash yields because of different heating procedures, combustion of unburned carbon, and decomposition of materials in the residue.

1.1 These test methods cover the determination of the mass loss from solid combustion residues upon heating in an air or oxygen atmosphere to a prescribed temperature. The mass loss can be due to the loss of moisture, carbon, sulfur, and so forth, from the decomposition or combustion of the residue.

1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.