Abstract: A downhole gas generator can be ignited downhole by an ignitor mixture combining with an oxidant. The ignitor mixture is provided by an ignitor subsystem. In one embodiment, the ignitor subsystem bubbles gaseous fuel through a chamber of liquid pyrophoric. The chamber is heated, wherein the fuel obtains a vapor content of the pyrophoric, forming a gaseous ignitor mixture. In another embodiment, gaseous fuel is turbulently injected into a chamber. Liquid pyrophoric enters the chamber through an orifice. The fuel passes through a nozzle wherein its pressure is reduced. This pressure drop is imposed on the pyrophoric, wherein the pyrophoric is drawn into the chamber. The fuel mixes with and atomizes the pyrophoric to form an ignitor mixture.