點解火冇氧氣就燒唔着?

因為『火三角』是起火的條件。
火三角就是可燃物、助燃物及足夠高的溫度。

狹義的燃燒是物質和氧產生氧化作用，同是可以產生光和熱，這便是燃燒。

Becoz of Fire Triangle: Fuel, oxygen and heat. Without one of them, fire cannot start.

to create fire, you need to supply heat to start it, then the fuel need oxygen to oxidize. This is essential for combustion.

Excess oxygen: create CO2
Lack of oxygen: create CO - carbon monoxide
Without oxygen: create C - carbon soot