Gas Filter

You have probably connected outlets of the filter with a pipe.

2 hours ago, Kasuha said:

You have probably connected outlets of the filter with a pipe.

I do not.  I have one line, with one filter in it.

2 minutes ago, Moyranian said:

I do not.  I have one line, with one filter in it.

Screenshot would help.
 

13 minutes ago, Risu said:

Screenshot would help.
 

Now that I try to recreate it, it's not happening. I'll see what happens once the pressure gets low.

55 minutes ago, Moyranian said:

Now that I try to recreate it, it's not happening. I'll see what happens once the pressure gets low.

Are you sure you didn't pipe the filter like this?

12 hours ago, Risu said:

I think the problem was the pipe filter doesn't delete the pipes beneath it, so there was a second airflow beneath it.  I'm not sure though.

Building anything does not destroy any pipes/wires, if you lined up the filter and the pipe everything will be connected. So unless you can reproduce this without the pipes going through the filter like in the screenshot lets just assume that's what you did.