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I am replacing a gas oven igniter. On my model I had to remove the whole bottom burner in order to unscrew the bracket. I was very surprised that the burner is very loosely attached to the gas valve. In fact there are huge open holes near the attachment. How does it work? Why doesn't the gas escape through that, but instead goes directly into the burner?

Burner attaching to a gas valve

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It is called primary air mixture, the gas is injected from the port and draws air alon with it as primary gas air mixture secondary air is used at the burner head – UNECS Dec 14 '12 at 10:47
Expanding on what UNECS said; preferably, there is no air (oxygen) in your gas lines. As you need oxygen to combust a gas, that opening allows air to come into the mixture. I've seen a similar setup to this working on a central air furnace. Its perfectly normal for there to be an opening there. Pressure keeps the gas flowing in the direction it needs to go. – lsiunsuex Dec 14 '12 at 11:45
@UNECS that should be an answer. – The Evil Greebo Dec 14 '12 at 13:21
@lsiunsuex yours too. Silly people. ;) – The Evil Greebo Dec 14 '12 at 13:21
the reason why it doesn't create a gas leak is the venturi effect – ratchet freak Dec 14 '12 at 21:54
up vote 4 down vote accepted

(based on comments)

The opening is called a Primary Air Mixture.

Gas flowing through the line from the service point passes this opening, picks up air (oxygen), mixes and is ignited at the burner head.

Pressure in the line keeps the gas flowing. As there should not be air (oxygen) in the gas lines, this port allows the proper amount of oxygen to mix into the gas allowing ignition. Most gases (all?) require oxygen to burn.

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