Reuben's Home Inspection Blog


Some Furnace Certifications Are Useless

I don't think I'll be recommending any more furnace certifications.  Heresy you say?  No, I have good reason not to.  I started out meaning to write a blog about what's involved in furnace certifications and who does them, so I contacted 40 local HVAC contractors.

I was shocked at most of the responses I received.

An Easy Call

Cracked Heat Exchanger

When I inspect a furnace and I find a serious problem, such as a cracked heat exchanger, it's easy for me to tell my clients what to do: replace the furnace.   The photo above shows a cracked heat exchanger on a furnace, looking at it from the back - this GE furnace had a removable back panel that gave me a good look at the back of the heat exchanger, and made finding cracks very easy.

Cracked Heat Exchanger
Cracked Heat Exchanger

The Grey Area Unfortunately, diagnosing a cracked heat exchanger is almost always a difficult if not impossible task.  Home Inspectors are usually only able to see the burner side of the heat exchanger, and this area is often dirty and rusty, making cracks very difficult to find.  The photo above shows a crack as seen from the inside of a heat exchanger, and it's one of the most obvious heat exchanger cracks I've ever seen - yet it's still tough to see.  Home inspection standards disclaim the inspection of the heat exchanger just for this reason, but I still do my best to look for problems.  When I suspect a crack, all I can do is recommend an HVAC contractor come out to confirm or deny the presence of a crack.

What Excellent HVAC Contractors Do  Many years ago, I attended a seminar put on by a very reputable HVAC firm, where the speaker talked about what was involved with a furnace 'certification', which was the type of inspection they would do when a Home Inspector suspected a problem.  The guy leading the class talked about using mirrors, borescopes, smoke bombs, leak seek tests, and basically dismantling a furnace to get a good look at the heat exchanger to check for cracks.  He assured us that if there was a crack to be found, they were happy to go out of their way to find it, and that's what a furnace certification was all about.

What Other HVAC Contractors Do  To gather information for this blog, I contacted 40 different HVAC contractors (23 responded).  The price for a furnace certification varied between $135 and $219, and almost every contractor said that a furnace certification consists of an Orsat test.  That's it.  An Orsat test measures CO² and 0² in order to determine the efficiency of an appliance, and that's about it.  It won't have anything to do with a crack.  After making all of these phone calls and sending all of these emails, I don't think I'll ever recommend another furnace certification.  The efficiency of a furnace doesn't have anything to do with a cracked heat exchanger.

Saint Louis Park has it right  I guess the City of Saint Louis Park has had it right for a long time; when they do their Point-Of-Sale Evaluations, they automatically require a certification on furnaces over 20 years old, and they also require a smoke bomb or leak seek test, which is specifically designed to test for a cracked heat exchanger.  I think I'll be recommending a lot of leak seek tests.

Don't Call CenterPoint  The local gas company, Centerpoint Energy, offers safety inspections of furnaces for $89.  Can you guess why the price is so low?  Because it's not a certification!  They won't do certifications on furnaces, much less smoke bomb or leak seek tests.  Almost half the time I recommend a furnace certification, someone ends up calling the gas company instead, and to no surprise, the gas company says everything is fine.  I called CenterPoint to see how it was so easy for people to confuse a certification with a basic safety check, and I was quite surprised. Here's how the conversation went:

Me: Hi, can I have my furnace inspected?

Centerpoint: Why, did an inspector suspect a problem with it, or are you selling your house?

Me: Yes, the people buying my house want to make sure it's safe.

Centerpoint: I'm sorry, we don't offer that type of service. You'll need to contact a private HVAC contractor.

The gas company was very clear about not offering certifications or anything close to that.  So how does the local gas company show up at the majority of houses that I'm recommending certifications on?  It's probably a communication problem.  I tell the buyer to get a certification, they tell their agent, that agent tells the seller's agent, and the seller's agent tells the seller.  The seller eventually hears "Get your furnace checked out".

From now on, I'll be recommending leak seek tests when I suspect a cracked heat exchanger.  One of the better companies that I contacted does certifications for $135, and they always do smoke bomb tests or leak seek tests when they suspect a problem.

Reuben Saltzman, Structure Tech Home Inspections - Email - Saint Louis Park Home Inspections


Reuben Saltzman, Structure Tech Home Inspections


Comment balloon 8 commentsReuben Saltzman • October 06 2009 06:26AM


As usual a very informative piece. I have never heard of the leak seek test or maybe it's a name unique to your area. Smoke bombs seem to be the norm out here.

Posted by James Quarello, Connecticut Home Inspector (JRV Home Inspection Services, LLC) almost 11 years ago

Thanks James.  A leak seek test requires access to the 'blower' side of the heat exchanger.  The tech sprays water on the heat exchanger on the blower side, and evaluates the 'flame' side for cracks.  Any cracks will become very obvious as water leaks through them via the capillary effect.  

I meant to include a video of this being done, but couldn't make it happen.  Hopefully I'll be able to post a video of this in a future post.  Smoke bomb tests will only find big holes in the heat exchanger... so they're better than nothing, but not my preference.

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) almost 11 years ago

I have seen a slight variation on that type of test. Salt is added to the water and sprayed into the burner chamber. This was on an oil fired furnace. After a few minutes a torch is held in front of the supply ducts. If there is a crack the salt will ignite in the air flow from the supply like little sparklers.

Posted by James Quarello, Connecticut Home Inspector (JRV Home Inspection Services, LLC) almost 11 years ago

Reuben, I have been having reputable HVAC guys tell me that ALL gas furnaces are going to have some amount of cracking of heat exchangers.  Obviously there are "bad" cracks and "inconsequential" cracks.  The reality is that in a properly drafting furnace you shouldn't have bad stuff in the air supply and a properly operating furnace should not be emitting carbon monoxide.  I think the only reason anyone is willing to sign off on these things is because they know this----the liability would be just too immense if it were not true.  What do you think?

Posted by Charles Buell, Seattle Home Inspector (Charles Buell Inspections Inc.) almost 11 years ago

Charles - The HVAC guys in your neighborhood must be very different than those here in Minnesota.  Any contractor or inspector around here would get hung for saying something like "inconsequential" crack.   

A cracked heat exchanger is a cracked heat exchanger.  There's no such thing as a 'minor' crack or a 'safe' crack. 

What do I think?  I think that a small crack couldn't really make much of a difference... but if the gas company, who has the lowest standards out of all the companies out there, will red-tag a furnace because of a tiny crack, then I'm going to treat it the same way.  

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) almost 11 years ago

Reuben, I am not saying that they would call them inconsequential---just that if it is true that all heat exchangers have some amount of even the tinest of cracks then it stands to reason that some of them had better be inconsequential:)  Note I am heavy on the "ifs" here:)  I sure don't know and am not sure who does.

Posted by Charles Buell, Seattle Home Inspector (Charles Buell Inspections Inc.) almost 11 years ago
Charles - I don't believe it's true that all heat exchangers have cracks, even tiny cracks.  Most don't.  I went through a training seminar put on by Ellis Prach (, and one of the things I came away with was that when a furnace develops a crack, it has failed.  

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) almost 11 years ago

Sounds like a good discussion on heat exchangers.  I know several cracked ones were found for my buyers on inspections.

Posted by Gene Allen, Realty Consultant for Cary Real Estate (Fathom Realty) almost 11 years ago