Factory-Made Air Ducts and Air Connectors

UL 181

1 Scope

1.1 These requirements apply to materials for the fabrication of air duct and air connector systems for use in accordance with the International Mechanical Code (IMC), International Residential Code (IRC), and Uniform Mechanical Code (UMC), Standards of the National Fire Protection Association for the Installation of Air-Conditioning and Ventilating Systems, NFPA No. 90A, and the Installation of Warm Air Heating and Air-Conditioning Systems, NFPA No. 90B.

1.2 The air ducts and air connectors covered by these requirements include preformed lengths of flexible or rigid ducts, materials in the form of boards for field fabrication of lengths of rigid ducts, and preformed flexible air connectors.

1.3 For the purpose of these requirements, air ducts and air connectors are classified as follows:

Class 0 - Air ducts and air connectors having surface burning characteristics of zero.

Class 1 - Air ducts and air connectors having a flame-spread index of not over 25 without evidence of continued progressive combustion and a smoke-developed index of not over 50.

 

Is duct pipe considered factory made?

 

You said the inspector said nothing. What then made you ask about class 1 air duct?

Is everything insulated well? I've seen inspectors ding an install if any sheet metal was showing (barring lined duct work) or the insulation just looked bad, like it would fall off.

Bottom line, the inspector has to have a reason for the red tag. Make a phone call and find out what that reason is.

 

"must use class 1 air ducts for supply" was his note. Not insulated, because drop is same "thermal envolope". Modern look has exposed duct, all in conditioned space. We added drops from existing truck line ti supply little cubicles.
Inspector was not concerned about insulation.

 

expandable aluminum is not an acceptable connector............................

 

Alumiflex is acceptable for your typical low pressure system where I live. Of course, it is always insulated for A/C systems.

 

You were also asking about duct tape. I don't think I've ever used duct tape on exposed duct work, always used a caulk or other high pressure duct sealant. But it is unlikely that is what the inspector is dinging you on. Still, a phone call is in order. Just ask him what duct work he is referring to.

It still could come back to insulation. For example, maybe he wants the plenum drops to the trunks to be insulated, even though it is in the same envelope. Keep in mind that if a inspector does not write some red tags, then he doesn't feel worthy. It is always in your best interest to work with the inspectors. Just talk to him and ask him what he wants.

 

he wants class 1 air ducts, then says it's in the IMC book. Thats all he will offer.

 

Well, okay, basically that inspector is just being an ass. Could be for any reason, maybe just a bad day. Or maybe he has had problems with you or your company before. Or maybe he thinks he is doing the world a favor by making you study the code book.

Quite frankly, since my specialty is emergency service, I don't do much on the install end anymore, and when I do, I'm just the helper these days. But I have run a crew before doing installs, and more often than not, I had approved prints to work from. But even then, inspectors can be an ass even after they have approved something.

So . . . I just put Class 1 air duct in the Googe search engine and it appears it has to do with a flammability rating. Here's one of the first links that popped up:

http://ulstandardsinfonet.ul.com/scopes/scopes.asp?fn=0181.html

Not sure if this is what you are looking for. It is short and sweet. Read it close.

So . . . What is flammable? Or are there connectors that may not be preformed at the manufacturer?

Ultimately, you may need to contact the wholesaler where you bought the goods. Tell them that you need the spec sheets for the products so you can show the inspector. I know it is a hassle, but that is how the inferior inspectors justify their existence. A qualified inspector who really knows what they are doing will just tell you what they want once you humble yourself and ask.

 

Some of my material is Class zero. I thought would be better then class one, but it isn't class one.