 The flame is significantly less luminous than hydrogen or methanol flame and is only visible due to the turbulent hot air it generates.Isopropyl nitrate was previously used in a jet engine rapid starting system for military interceptor aircraft (a requirement for fast scrambling, as it provided simultaneous, near-instantaneous engine starting for twin engines) and was known as AVPIN.The exhaust fumes from an AVPIN monopropellant engine may themselves be explosive, if mixed with further air.