UN No. 1829 sulphur trioxide shall be inhibited. Sulphur trioxide, 99.95% pure or above, may be carried without inhibitor in tanks provided that its temperature is maintained at or above 32.5 C. For the carriage of this substance without inhibitor in tanks at a minimum temperature of 32.5 C, the specification "Transport under minimum temperature of the product of 32.5 C" shall appear in the transport document.