A nanoscale antiferromagnetic gas sensing apparatus and methods of measuring gas using the apparatus are described. The use of the magnetic properties of an antiferromagnetic material as gas sensing parameters explores the concept of magnetic gas sensing. According to a preferred embodiment, a nanoscale magnetic hydrogen sensor apparatus is developed based on varying of the saturation magnetization and remanence of nanoscale antiferromagnetic hematite with hydrogen flow. For example, the saturation magnetization and remanence of nanoscale hematite has been shown to increase one to two orders of magnitude in the presence of flowing hydrogen gas at concentrations in the 1-10% range and at 575 K, indicating that a magnetic hydrogen sensor using hematite material may be practical and useful for detecting hydrogen in various environments such as those wherein production, storage, transportation, and/or vehicle use of hydrogen is being conducted.