When I first started doing plumbing in 1971----at least for money----venting island kitchen sinks was a bit of a problem. Every plumbing fixture needs a means of venting the drain line so that water doesn’t get sucked out of the trap----which could allow sewer gases to enter the home. Somehow sewer gases and the smell of fresh baked bread or homemade pizza just don’t go together. We had to create all kinds of strange assemblies of pipes to create this venting----it worked, but was time consuming to construct and took a lot of additional pipe. Pipe and time equal money. Along came the “auto-vent” or “air-vent.” This mechanical device had a spring loaded gasket inside that would allow air to flow into the pipe but not let sewer gases out-----or, in the event of the pipes flooding, the device would not allow sewage out either. How is that for a plan? These vents could be installed right at the fixture location----saving tons of time, pipe and money. Unfortunately most jurisdictions did not allow them----except in the mobile home industry----where they are still allowed----go figure. Here is a picture of one of these vents that I found installed at a kitchen sink in new construction that had to be replaced after the inspection. If you can see a spring inside the cap, it is an Auto-Vent. At some point in the 90’s, a new type of air-vent could be found in the neighborhood----called the Air Admittance Valve---or AAV. AAV’s quickly gained acceptance in most jurisdictions and are now widely used. These valves are different from Auto-Vents in that there are no spring mechanisms that can fail and they have screens to keep out critters. They have a simple EPDM diaphragm that allows air into the drain under negative pressure and seals tight under positive pressure (trust me you don’t want to know what the initials stand for---synthetic rubber for short). AAV’s, to meet approval for use in residential construction, have to demonstrate that they can go through 500,000 cycles without ever passing gas----roughly equivalent to 30 years----man I sure wish I could do that! Here is a picture of a modern AAV on a laundry sink drain. While a really simple device, they must be installed within 10 degrees of vertical, they must be installed on the welded-pipe side of the trap, they have to remain accessible and they cannot be the only means of venting the plumbing system. These Air Admittance valves come packaged with a rubber band that needs to be removed at the time of installation----I frequently find them with the rubber band still in place----rendering them non-functional. So, never----ever----pass gas again! Now what fun would that be? 
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Be careful what you wish for, Charlie. You might float away like a balloon or go up in flames like the Hindenburg.
GREAT TIP! I can tell you know your industry!... I can tell you did your
research. If I come in contact with someone looking in your area I'll
be sure to send them your way.
Kevin Conery
kevin@citymtns.com
1-800-931-9947
Your Summit County Colorado Realtor
Find Your Colorado Dream Home Today
Glenn, yes it would be a bummer having to walk around avoiding all sparks and ignition sources.
Michael, so this would be a little like letting new brain cells in as you kicked the old ones out?
Kevin, thanks for the comment
Charlie, thanks for this post. I love learning about these kinds of things. It only helps me in being a better realtor. I loved the humor as well.
Cal
Thanks for the post Charles... You have solved a problem for me and a recent buyer!
Charles, you are a mountain of information (pardon me if I vent). I look forward to reading your posts all the time.
Cal, thanks
Dean, that is too cool----glad to help
Katherine---glad you find them interesting
Clever headline Charles! Love it. Great information!
Diane, I am always looking for that "hook"----potty talk usually works :)
Very nice. That link will go in my reports.
Thanks again. I just got that in the body of my text. I like using blogs I have written or you have written. I know they will be there when my clients try to go to the link. So many of these sites, even government sites, change links and what a pain it is to try to correct that when I use many links in reports.
why then Blazing Saddles would never have been filmed.
One of our daughters needs this post. Okay I actually mean the drains in her house need this post. :)
Better not show this to my wife. I am not sure I want one installed. I am not sure how comfortable it would be.
You need to be a headline writer for a major newspaper Charles!
Charles, are you saying that running loop vents behind the sink was a pain in the butt. Those are my sentiments too.
Steve, I think Nutsy needs one of these things
Alan, I think the saddle horn could easily be turned into an AAV
Kate, wouldn't beano be cheaper?
Gene---they come in different sizes :)
Craig----do they get paid?
Jack, venting has gotten a lot simpler with these things that is for sure.
Hi Charles, a very interesting devise. I have not seen them here in CA. But I must say it is certainly interesting ( will check out ), not to mention that your title drew me right in, :-).
As an aside, I really like the clean finished cabinet under the sink. They don't do much of that here ( CA) either.
I find it very funny that you find them with the big orange rubber band still around them after installation.
William, I would be surprised if they are not available in your area.
Jim, at least that bright orange sticks out like a sore thumb
#19 comment is a reflection of what is not happening in Southern California. I learned a lot and thought you made it easy to understand.
Good info - I never knew the difference between the two. Here in Minnesota those AAVs aren't allowed. I see very few of them.
Lorraine or Loretta, thanks
Reuben---I am surprised you can't use them there----lots of differences around the country.
Mr Charles,
Can you save the rubber bands for me and Wheat, they are wonderful trampoline springs.
Nutsy
Nutsy sure----but they make a way better muzzle
As always....get catchy title and an informative post.
I've never heard of it but now I know. Plumbers can't read I guess with the 'warning' remove this rubber band?
#25/#26 or noose. heheh
Diane, thanks
Lyn---or more likely Uncle Harry :)
Kate---placed just right it would likely cover both breathing apperatus :)
I for one would like to see what you look like after 30 years of not passing gas...
Or maybe not!
I had an inspection once, new construction, where they put all the drain apparatus under the kitchen sink, but handily forgot the cap (AA valve)! It was a new home so there was no evidence yet, but a week after moving in I bet I would have gotten a call about the kitchen smell. The supervisor even chuckled!