CH3ONO is synthesized in house using air-sensitive techniques according to previous literature, with no further purification necessary. Briefly, sodium nitrite (ACS grade, 97%) is dissolved in a solution of water and methanol (HPLC grade, >99.8%) and allowed to stir at room temperature under an inert atmosphere. Then, hydrochloric acid (ACS grade, 36.5-38%) is titrated into the aqueous solution. The gaseous CH3ONO that evolves from the solution is passed through a drying tube before being collected in a liquid nitrogen trap. After the condensed CH3ONO sublimates at room temperature, it is immediately diluted to concentrations less than 10% in N2 (Airgas, Industrial Grade), Ar (Airgas, UHP), or Xe (Spectra Gases, UHP) in a stainless-steel cylinder. CH3ONO is known as a highly flammable, heat-sensitive explosive. Therefore, we ensure each cylinder is diluted to concentrations of 10% or less in order to minimize the hazards of working with CH3ONO in a confined laboratory space.