A yellowish nonmetallic element, sometimes known as "brimstone." It is present at various levels of concentration in many fossil fuels whose combustion releases sulphur compounds that are considered harmful to the environment. Some of the most commonly used fossil fuels are categorised according to their sulphur content, with lower sulphur fuels usually selling at a higher price. Note: No.2 Distillate fuel is currently reported as having either a 0.05 percent or lower sulphur level for on-highway vehicle use or a greater than 0.05 percent sulphur level for off-highway use, home heating oil, and commercial and industrial uses. Residual fuel, regardless of use, is classified as having either no more than 1 percent sulphur or greater than 1 percent sulfur. Coal is also classified as being low- sulphur at concentrations of 1 percent or less or high-sulfur at concentrations greater than 1 percent.