What does the duckbill aka Dust Ejector Valve do on the heavy duty air cleaner?

[edporch]

I replaced the duckbill on the heavy duty air cleaner on my Grasshopper, as the old one just fell off and got lost.
How does this work?
What does it do?

 

[StarTech]

It is a dust ejector for the air filter. During some impluses from the engine dust is blown out. but it seals on vacuum from the engine to keep dirt out.

 

[edporch]

It is a dust ejector for the air filter. During some impluses from the engine dust is blown out. but it seals on vacuum from the engine to keep dirt out.

Thanks for the info.
That sounds like what my goto Grasshopper dealer told me today when I asked.
I just wanted to get a second opinion.