There is no other way to say this - this is a dangerous gas line installation.
This is unprotected flexible metal tubing generically called Corrugated Stainless Steel Tubing, or CSST.
There are lots of things swirling about its use and installation, from bonding and grounding to proper protection.
In this case it enters a furnace in an attic.
And does so dangerously unprotected.
Flexible gas tubing as shown in the photo should never pass through the metal wall of an appliance.
Why? Eventually the vibrating metal edge of the hole may cut through the thin, soft tubing!
What happens if it does?! What happens if it does and there is a gas leak?!
This installation was dangerous from the start and not approved when it was done.
So why was it plumbed this way? Apathy or ignorance. Either way, with natural gas, one shouldn't be playing with improper installation in any fashion.
When I see this on any installation (and UNFORTUNATELY I see is a lot), I include this on my report:
Flexible metal gas tubing passes through metal wall of a gas appliance, and here the gas furnace in the attic. This is prohibited as the vibration of the motor of the appliance can cause the metal wall to cut into the flexible tubing, causing a leak. A solid tube is required. This is from the International Fuel Gas Code: IFGC 411.1 #2 states: Semi-rigid metallic tubing shall not enter a motor-operated appliance through an unprotected knockout opening.
I don't invent standards and rules. But sometimes I need to invoke them on my reports. And I don't say what needs to be done, leaving it instead to a knowledgeable and caring professional to make the repair.
My recommendation: danger is danger. I got to including some codes and standards on my reports because builders would argue with my report on new construction inspections. But this installation has been here since 2001. Nonetheless, it is time to change it. The house is vacant and a new occupant wants to move in! Any such move should be done with peace of mind. And safety...
Jay Markanich Real Estate Inspections, LLC 
Based in Bristow, serving all of Northern Virginia.
Office (703) 330-6388 Cell (703) 585-7560
Morning Jay, your statement "apathy or ignorance" sure fits the bill on this one.
I can't think of any other reason, James.
Good morning Jay,
This is an installation that was often made which prompted the code to be written. Time to correct a dangerous situation..buyers do want to move into their home with peace of mind!
I don't know which came first Dorie, but suspect you may be right!
Oh yes, no sense playing around with dangerous gas lines. It must be fixed.
The agent contacted me and there is no argument here Debbie. And they say it is something nobody knew about, which I am certain.
Oh my. I changed out my gas logs over the weekend. It always makes me nervous to deal with a gas appliance. No leaks, but I check it more than once before I use it.
thanks Jay....I learned something new today...have not seen this yet but I am sure I will at some point.
Not good here Mike. And gas log fireplaces do need to be checked.
I see it often Ginny. And too bad that I do. It's very dangerous.
This does look dangerous JayMan, not something that can be overlooked at this point.
What evils lurk within the home? Jay will reveal them sooner or later
It's rusting too Tom, maybe from disimlar metal contact or just humidity. But that probably adds another layer.
Richie - this has been lurking for sure. For a while!
Natural gas and electricity are two things to never install haphazardly! It's a good thing you caught this before disaster struck!
Jay Markanich Great catch of a potential disaster. People do not realize how easily aluminum will stress and be cut under these circumstances.
And, Nicole, that could strike any time!
S&N - the flexible tubing can easily be cut.
Now you know the UN-caring repair guy is going to wrap that flex pipe with duct tape!
Good catch Mr. Jays!
This definately looks like something that needs immediate attention. I am glad you pointed out this dangerous condition .
And veeeeola, problem solved! No doubt Fred.
Thanks Joan. My clients are glad too!
Jay, Just a little sleeving will make you better ;)
We sure need long sleeves here Don - it's pretty cold!
Oh, gas lines, um, sleeve or no sleeve, I always prefer to see solid tubing going into appliances.
Very dangerous. I appreciate you posting this so that we're all aware.
Thanks Liz. The idea here on AR is to inform!
Good evening Jay. I have never seen a gas line installed this way. The local codes guys are really up on this.
I imagine they are up on it here too Michael, that is if they are UP in the attic space...
I see it a lot.
Thanks for sharing one more thing to make us all better informed.
Margaret - there are so many things that could be shared! We try...
Jay, Thanks again for sharing this valuable information. It is always a pleasure to read your posts. The info you provide is always so useful.
all the best....
Thanks Bill. I appreciate it as I try to be informative!
Jay Markanich playing with life of people is not good! This is really bad - just wondering how it passed the town inspection?
To inspect it they need to go into the attic Praful!
I have never seen a county inspector with a ladder.
I will dabble in plumbing and electrical repairs all day, but draw the line when it comes to gas appliances. It's one thing to clean up a small leak, another it a gas leak goes wrong.
Me too Stephen. However, I think this was installed by the builder's "reputable" sub contractor.