A jar of CO2 is used as the flame distinguisher. As the density of CO2 is heavier than air, the CO2 will fall off the jar as if water is poured out. The CO2 will isolate the flame from air, eventually the combustion could not continue and the candle is out.
In this experiment, the single-mirror co-axial schlieren setup is used. The system contains the following Luftvis equipment:
Schlieren Mirror: Luftvis-150 Pro
Light Source: Luftvis LED-Mini