About Bunsen burner.

It is because it might explode if we light the match after turning on the gas tap.

As the gas is invisible, we might omitted that the gas is accumulated to a level that can cause an explosion before we light on the match. It is dangerous to ignite a light after turning on the gas tap for a long time.

Town gas contains carbon monoxide which is toxic. If you turn on the gas tap before light the match, some toxic town gas will enter the air.

Since the fire of the burnsen burner cannot easily see , if some people hit them carelessly, they will get hurt.

因為本生燈所噴出既氣體/火 是黃色的(未開個蓋時),如果有人唔小心咁hi 到,會受傷.所以點左火柴後先開本生燈係安全d既

Burn before the gas come out to avoid too much gas exisitng in the air and burn your hand or even explosion