Robin Jade Conde

PODCAST: Should home inspectors test for carbon monoxide?

Carbon monoxide (CO) leaking inside the house is a serious concern. How are they tested? What harm will it cause? How do you properly manage a furnace? 

According to Reuben, experts in the field conflict with each other on how to properly test CO on furnaces. While it is not required in the standard inspection process, he shares the common and right way to do it. Tessa discusses the types of furnaces, how they work, as well as how to test them. They also talk about the proper equipment to use and its calibration. 

 Reuben also shares the downside of shutting off a furnace and their threshold for the servicing needs. On the other hand, one type is never tested because it always yields an erroneous result.



The following is a transcription from an audio recording. Although the transcription is largely accurate, in some cases it may be slightly incomplete or contain minor inaccuracies due to inaudible passages or transcription errors.


Bill Oelrich: And one of the issues with gas log fireplaces is CO leaking into the house. And that prompted us to start talking about testing CO on furnaces, which is kind of a sticky situation for the home inspection industry.




BO: Welcome, everyone. You’re listening to Structure Talk, a Structure Tech presentation. My name is Bill Oelrich, alongside Tessa Murry and Reuben Saltzman. As always, your three-legged stool, coming to you from the Northland, talking about all things houses, home inspections, and anything else catches our attention in a given week. So, on last week’s episode we were talking about gas log fireplaces, and one of the issues with gas log fireplaces is CO leaking into the house. And that prompted us to start talking about testing CO on furnaces, which is kind of a sticky situation for the home inspection industry, because it seems like you can get it right nine out of 10 times and the one time that it doesn’t go right you are firmly in front of a bus.




BO: So…




Reuben Saltzman: Yeah, you get run over.


BO: Yeah. I should say not getting it right is sort of a very subjective thing because Reuben, as you know, there’s how many different ways to test a furnace, and how many different opinions on what’s the right way to test a furnace? 


RS: I’ve learned the right way to do it about 10 different times, and they’re all different.




BO: Okay. That’s helpful.


RS: Oh my gosh, it’s so frustrating. There’s so many experts in the field who insist, “This is the way to do it. I’ve been doing it for this long, and this is how you definitely do it.” And they conflict with each other. And I don’t know of any authoritative document that just says this is the one true way to do it. It’s like, when you go to the building code, there is one building code for say, Minnesota, and there might be different interpretations of the stuff, but the language… You have language to go back to. But we don’t have the same thing when we’re testing CO on furnaces. It’s mostly like, what is the most common way of doing it? What do most people nod their head in agreement at? And that’s what we’re doing when we test.


BO: Well, should we start there, Reuben? What is the one thing we can all agree on at this moment in time when it comes to testing furnaces? 


RS: Well, one thing we can agree on is that testing for CO, carbon monoxide at a furnace is not required by any home inspection standard of practice. Home inspectors absolutely do not need to do this. It’s more one of those things where, what does everybody else in your neighborhood do? Is this common practice? And we’ve discussed this. I was the president of the local ASHI Chapter here in Minnesota for probably about five years, and there were a few different meetings where we would do an informal poll, and I’d say, “Alright, while, we’re on CO and practices, raise your hand if you test for CO.” And man, everybody in the room raises their hand. It’s like, this is just standard practice in Minnesota. I’m sure there’s some inspectors in Minnesota who don’t do it, but they’re the exception. Everybody tests for CO. So, this is standard here, even though it’s not required. We know that for certain.


BO: Okay. There’s one other hard and fast rule, and so I’m gonna throw this softball up to you. Where do we always know that this is a bad furnace? 


RS: I wanna say Lennox. [chuckle] Whisper Heat.


Tessa Murray: Lennox Whisper Heat.




RS: Yes.


BO: Okay, apparently my softball was not as big as I thought it was gonna be. [laughter] Okay…


RS: Alright.


BO: It’s 400 parts per million in the exhaust gas.


RS: Yes, yes.


BO: And so if you do test, and if you use diagnostic equipment for testing, or a gas analyzer… I should be more specific so people don’t get upset. If you use a gas analyzer and you get to 400 parts per million when the furnace is running at high fire, that’s a problem.


RS: Yeah.


BO: Everybody agrees to that.


RS: Yes, that is a published standard that is in writing. It’s in the Minnesota Fuel Gas Code. They don’t spell it out quite that way. I think maybe the new version of the code does, but the way it was always written in the code was that it can’t be more than 0.04 100th of a percent, which equals 400 parts per million. They didn’t actually say 400 parts per million in the code, it was 0.04%. It can’t exceed that. And if it does, it’s bad news. And that is… I mean, that’s a standard for all furnaces, for boilers. That is a magic number. If it’s above that, when we’re doing a home inspection, we… If it’s in the summer time, we’ll go to the furnace shut off switch and we’ll shut it off, and we’ll put a call into the listing agent, or leave a note for the homeowner. We’ll do whatever we can to say, “Hey, this equipment isn’t safe to operate.” But if it’s the dead of winter, and there’s nobody home, you know, if we shut that equipment down, what’s gonna happen two days from now? Well, the house is gonna freeze. It’s gonna be a winter wonderland, and we’ll have destroyed the house. So, we won’t shut the equipment down at that number, but that is a magic threshold that can’t be argued with.


BO: And we don’t have any authority to shut off a furnace, by what we do? 


RS: No, I mean… No, we don’t.


BO: But a heating contractor can red-tag a system? 


RS: Yeah, they can red-tag it. And I mean, technically, we could red-tag it too. There is no authority behind a red tag. A red tag is just a tag that’s colored red. There is no National database of red-tagged furnaces. Nobody’s gonna come in and get you in trouble for flipping it back on, but boy, if you turn a furnace back on that has been red-tagged and somebody dies, I would think somebody would be in some legal trouble for that. It just… It’d be foolish. But when it comes to authority, I don’t know if there’s any authority behind a red tag.


BO: Now, one other thing I wanted to bring up in this conversation, sometimes it’s equipment too, because contractors, inspectors, they all have equipment that they like to use. We use a brand called Testo…


RS: Yeah.


BO: And there’s other types of equipment out there. And so, are you familiar with calibration on this type of equipment? How often should it be calibrated? 


RS: The standard that manufacturers want you to do is once a year. Now, we don’t calibrate our stuff religiously once a year. We cross-check our equipment against equipment that has been calibrated, at least monthly. We are always cross-checking our equipment with other known good equipment, and we send them in for calibration probably about once every two years. But we’re always double-checking it to make sure they’re accurate.


BO: The only reason I bring that up is because in the past, if we run into an issue where we’ve tested a furnace and somebody from the office will go out and re-test, because the conversation usually goes like this, “These people don’t know what they’re talking about. They should have never told you that. Blah, blah, blah.” And then an angry homeowner, they call our office and we respond, so at that point, somebody like me would go out to the house and I would bring all 16 of our Testo and test, [chuckle] the furnace with each and every one to prove that, number one our equipment isn’t bad or whatever. And so, that was always one of the first things that a contractor would say is, “Well, when was the last time they had their equipment tested, do they even know what they’re doing with their equipment?” And so, it’s a sore spot. I don’t mean to bring it up, but it was a sore spot.


RS: And no, you’re absolutely right and this is one of the reasons why a lot of home inspectors don’t like doing this, especially, if you’re a one-man shop and you don’t have a big inventory of tools that you can cross-check against and double-check your results if you’re not sure, that’d be a good reason for a one-man shop home inspector to really be leery of doing this type of testing at all. Because it happens so often that people will throw you under the bus, and there’s this assumption that because they’re an HVAC contractor, their equipment is somehow better than ours, and theirs is accurate and ours is not. But I’ve personally been involved in probably a half dozen transactions where I found high levels of carbon monoxide at a furnace, I called it out, then later on, the contractor says, “No, it’s fine.” And then we figure out, “Wait, whose was last calibrated?” And ours was and they’re wrong about it, and they end up sending to somebody else on this, they say, “Oh yeah, our equipment was off.” So, it’s not like this is a one-way street, but there’s a perception that because they’re a contractor, they are right.


BO: Yeah. And I think to your point, when you talk about piles of equipment, they often have a lot of it, and I know there is a very large HVAC contractor in town that they will not red-tag something unless it’s verified with multiple testing units to prove that. “No, this isn’t off, this isn’t because our equipment’s off, this is because it is out of line here and it needs to be fixed.”


RS: Yeah. Yeah. And you know, Bill, while you’re talking about equipment, and we’re talking about that magic number 400, I think it’s important to note that a lot of equipment out there, a lot of CO testing devices don’t actually take the right reading, because there’s two numbers. There’s the raw amount of CO in the flue gas, and then there’s the air-free number. If you ever do a CO test on, say, like a power vent water heater, and you’re testing for just raw CO, the number is always gonna be really low, because you’ve got this draft fan at the top of the water heater that pulls in a ton of household air, and a large percentage of the air coming out of that exhaust terminal is gonna be household air and it’s gonna be very diluted, and so your CO level is gonna be very low. But if you have a fancier combustion analyzer, it actually does a calculation and it figures out how much free air do you have in here, and then it subtracts all of that air to give you the actual number of the CO that’s coming out of the flue un-diluted. So it’s giving you a much more accurate number, it’s the air-free number, and that’s the number that’s referenced in the code, is the air-free number. So if you’re just taking a plain old CO tester and it can’t do that calculation, you don’t know. All you can do is guess.


BO: Wow, that’s very, very technical.


RS: Yeah, so that’s why we use the ones we use, that’s why we don’t use straight up CO-detectors, we use combustion analyzers. Devices that will check all these different things, and for any home inspectors out there doing it, my advice would be, don’t use a straight CO tester, use a combustion analyzer that checks this.


BO: So Tessa, what does it look like in training when new people come on, how are you teaching them to work with these furnaces? 


TM: I think the first thing that we talk about is all the different types of furnaces out there and types of boilers too. Because depending on the type of furnace, if you’ve got a natural draft furnace or you’ve got an induced draft furnace, or you’ve got a sealed combustion or high efficiency, you test them in different locations depending on the different type. So that’s kinda the first thing we talk about, just the different types of furnaces and kind of how they work and how you test them. And I think we… Have we talked in another episode about all the things we do to actually test a furnace? I know we’re talking just about CO today, but we talked about doing temperature rise and…


RS: Yup.


TM: And taking off the panel covers, looking inside for rust or signs of moisture or anything like that, checking the furnace filter. We do all those things, we talk about that in training too, but then we talk about the proper location to do a CO test, and when you should do a CO test. It’s very important that you do it at the correct time, rewind, if there is a “Correct time,” but you wanna make sure you don’t do a CO-test like two minutes after you turn on a furnace, that’s too soon and you won’t have an accurate reading. Reuben, you can probably quote code on what that says, I can’t, but I just know that you need to let that furnace get to what we call a steady state before you do that combustion gas test on it.


RS: That’s… Tessa, you’re exactly right. It needs to get to steady state, and I’ve heard some people say, Well, you should only do a CO test after it’s been running for 10 minutes or 15 minutes, or blah, blah, blah. And you’re making stuff up. It’s not about how long the furnace has been running, it’s about getting into steady state, and it means that the flue temperature is not rising. You know, the flue or the vent, whatever, the exhaust gases are gonna keep getting warmer and warmer, and eventually that temperature is gonna plateau, it’s gonna stop rising. Once it stops rising that’s where you do your test, it’s at steady state.


TM: Can I ask a question? We just had an HVAC contractor come in and do a training session with us at one of our company meetings recently…


RS: Yup.


TM: And do you remember what he was talking about with doing that test at steady state on furnaces that have different modulations or stages, I should say? 


RS: Well, if it’s a two-stage furnace, and we see a lot of those, it’s best to do the test when the furnace is on the second stage, and for most of those, it’s gotta run for 15 minutes. And if the thermostat is still calling for heat after 15 minutes of continuous operation, it’s gonna go into high fire mode. It’s gonna go into the second stage, and that’s where we wanna test it. So, when we’re dealing with a two-stage furnace, yeah, we definitely wanna run it for at least 15 minutes before doing our test.


TM: Yeah.


RS: Now, if it’s a multi-stage, and I don’t know if I’ve ever seen a multi-stage ever, I guess, this is a furnace where it just keeps stepping up, maybe it might start at 40% capacity and then 41, 42, 43. For that, I have no idea, Tess.


TM: Gosh. Well, I think I’ve only seen as much as a three-stage furnace, but that’s helpful to know. To get a two-stage furnace to hit the high stage, that’s gonna be at least 15 minutes, do you crank the thermostat up at least 10 degrees when it’s a summer day outside, it’s 90 out and you let that furnace run for 15, 20 minutes? 


RS: Yeah. I don’t know how else you do it, and…


TM: Yeah.


RS: And that’s why we’ve got home inspectors on our team, and we talked about it, kind of our procedure for how we go through a house, and there’s some inspectors on our team who really want to do that test at the beginning of the inspection, ’cause they feel like well, the house is gonna get really warm, and then I know that the furnace will have gotten as hot as it’s gonna get, and then I can turn on the AC and by the time the occupants get home, it should be nice and cool again. And it makes perfect sense, I understand why they like to do it that way.


TM: Yeah, it does make sense. I always used to do it the other way, [chuckle] and I think that was fine too, but as long as you’re letting that furnace get to steady state, whatever that may be, that’s when you wanna do that CO test.


RS: Yup.


BO: I was getting worried. I used the word high fire or the words high fire, and I was like, “Is somebody gonna call me out?” But you fixed it already. [chuckle] You fixed it with this two-stage furnace, so thanks, I appreciate it.




TM: Another thing too, I think that it can get confusing for inspectors is where you do the test. And again, it depends on the type of furnace. I think one type that usually throws inspectors, I see this and Reuben, I think you can speak to this too, looking for pictures for your latest blog of where you test a natural draft furnace.


RS: Yes, and you’re talking about a furnace that doesn’t have a draft inducer fan.


TM: Yeah.


RS: They’re few and far between these days. There’s not a lot of them left out there, but those all have a draft hood and they are going to have somewhere usually between about two and six ports, and you need to test every one of those parts. It’s gonna be a matter of taking your metal probe and sticking it up inside there and testing cell number one, and then wait till you get a good reading, move it over, test cell number two, and you gotta test every one of those different cells, because you’re sticking your probe in before it mixes with the air at the draft hood. You can’t just stick it in the flue.


TM: Yeah. And for anyone that doesn’t know what this type of furnace looks like, it looks like a standard furnace, but on the upper cabinet, there’s this grate and this opening that you can look up into and when you look up, you can see all these chambers, like you’re looking into the heat exchanger cells, basically, across the top in a horizontal line.


RS: Yup.


TM: So you’re sticking that probe up through that draft hood opening into each chamber and doing a measurement.


RS: Exactly. Yeah.


TM: Yeah.


BO: That’s an old furnace, right? 


TM: Yes. Yes, typically.


RS: But they’re still out there.


TM: Yeah. Like, would you say they probably stopped making those in the late ’80s maybe? 


RS: I don’t know. Maybe mid ’90s, I’m not sure Tess.


TM: Okay. Yeah. Yeah. But they’re old. I mean, if you come across one of those, it’s probably safe to say they’re at the end of their expected serviceable life, but…


RS: Yes. Yup.


TM: We still test for CO.


RS: Still test. Yup.


TM: Yeah.


RS: Alright, so Tess, what about if it’s got a draft inducer, where do you test there? 


TM: For draft-induced furnaces, you want to test that flue gas in the flue about 6 inches above the hood, and ideally, I think no more than 18 inches.


RS: But you said hood, but you meant to say draft fan of course.


TM: Oh. Draft fan, thank you. [chuckle] Yes, we can rely on you for your technicalities.


RS: Yes.


TM: Thanks for fixing that. And then you wanna make sure that you’re not drilling into a bend. Like, if that flue takes a turn or something, you don’t wanna take a measurement right in a bend. And you wanna stick your probe kind of into that flue and have it go kind of right in the center of the flue, I believe.


RS: That’s right.


TM: Now, I’ve heard other HVAC contractors, Reuben, what do you think about this, taking measurements across the diameter on the inside of the flue and taking the highest measurement. But I’ve always just stuck it right in the middle of the flue perpendicular, making sure that it’s exactly perpendicular with the flow of the exhaust gas.


RS: Well, it depends. How’s that for a good answer, Tess? That your favorite.


TM: Yeah, that sounds…


BO: It sounds like a perfect answer for Tessa.


TM: My favorite answer.


RS: What it depends on, if it’s a furnace, if we’re talking about a furnace, you just stick it in the middle of the flue, but if it’s a boiler and most boilers are gonna be natural draft, you’re gonna wanna stick it all over that flue. You wanna put it on the far left side, take a read in there, move over to the center, move over to the right side. You gotta move your probe around, and we did some training at somebody’s facility once, and they had a perfect demonstration of that, where you put it on the left side of the flue and the CO was very low. You move it over to the right side and it just sky rocketed. So on a furnace in the center, but if it’s for a boiler, you wanna move it around inside there.


TM: Why is that? Just ’cause it’s a bigger flue, bigger diameter? 


BO: It’s because there is no fan that’s gonna swirl all those gases around and mix them up.


TM: Oh, and mix it. Okay.


RS: They’re just rising up through gravity.


TM: That makes sense.


RS: And I mean, boilers are gonna have different burners, and you could have one burner that’s really bad and one side of that flue might have really high levels of CO.


TM: Interesting. Oh, one thing I forgot to mention too is we don’t drill through double wall B vents either, we only drill through single wall.


RS: Yes. And most of the time we don’t even drill through those because there’s almost always a test port there where somebody has already done it, and they’ve covered it up with metal tape and we bring metal tape along with us, and after we make a hole, we put the same metal tape right back over the opening. And I will say it’s not just any metal tape, there’s always the generic stuff at the store and then there’s the UL listed stuff, and there is a difference. You buy that cheap metal tape and after the furnace has been running for a month, it’s gonna fall off the vent, it doesn’t stay in place, but you get the UL listed stuff and it’ll resist that high temperature of the flue and it won’t fall off, and that’s why we’re very picky about which tape all of our inspectors have with them.


TM: Yeah, I didn’t know that about the generic… Good thing I’ve never bought it, I’ve always stuck with the UL.


BO: It’s because you follow directions well.


TM: I do, yeah. And then that takes us to the sale combustion, high efficiency furnaces, and typically, you can identify those because you’ve got PVC pipes coming off on furnace exhaust typically. Although sometimes you might just have an exhaust pipe coming off with no intake, and on those… What we do at Structure Tech typically is we will test the exhaust gas from the exterior, where that exhaust pipe terminates on the outside of the house. Now, if it goes up through the roof. I mean, that’s another story, if it’s not accessible, you don’t do that, but we’ll try and test it from the outside. Now, we recently changed our policies and procedures, and just within the last year, we do allow inspectors to drill through the PVC pipe if they seal that hole up with a high temperature caulking, so I don’t know how many inspectors are on our team are doing that now.


RS: I’m going to say, nobody. I can’t imagine who would want to carry around, high temperature caulk with them. You need to make sure you got…


TM: Just walk around to the outside Bill said.


RS: Exactly, I don’t think we ever drill holes, but one trick for you, if you are gonna drill that hole, my advice would be to drill the hole down in the flue at a 45-degree angle, so that if anything ever does come loose, condensate is going to drip back into the flu and not leak out, there’s your little tip of the day.


TM: Oh, okay. Yeah.


BO: I’m trying to envision this. Now, Reuben is holding is drill at a 45 degree angle. Drilling down.


RS: I don’t do that. We don’t do that, we don’t drill holes in those flue, we test at the exterior…


TM: We try to for sure.


BO: There’s very few that are on the roof, and if they’re on the roof, they’re certainly accessible, I mean, what contractor’s gonna go put the only termination for this furnace, unless it absolutely has to be up there, like on a 12-12 pitch or something. It just doesn’t make any sense.


TM: I had a couple of those, I think in the past, but not very often, I’d say more often than not, it’s like a double wall B vent on an induced draft furnace and there’s no place to drill through it, and so we can’t test it.


RS: Yeah, that’s always a little frustrating when you come across that.


TM: We didn’t explain why we don’t. I wonder if anyone has questions about why you don’t drill through a double wall B vent.


RS: Yeah, the manufacturer says “Don’t”.


TM: Okay. [laughter]


BO: I like those simple instructions again, it’s very easy for me to follow that instruction.


RS: Yeah, it’s perfectly fine to do it on a single wall vent, but not on a B vent that’s the dividing line there.


TM: I suppose its just, the potential of getting combustion gas is trapped in between the two layers of metal and having corrosion and other things happen, right? 


RS: I would imagine you’re right Tess, because you don’t have any way of sealing off that interior vent. You’re still gonna have a hole there.


BO: That’s interesting, Saltzman laboratories have never tested for the reasoning behind this statement.


RS: That’s what I just don’t care enough about Bill, I know it’s hard to believe there’s some nit-picky detail I don’t care about, but that’s what a…


TM: I would think that that would be an experiment that would take years to actually see the potential damage that could cause.


RS: Yeah, I should have done that at my last house, I really should’ve and just taking it apart after five years and see what it looks like, but I didn’t. And you know what, there’s one other thing we didn’t touch on, we talked about the 400 threshold, but then what about if it’s 300? Is that okay? Really? No, you talk to pretty much any heating contractor and they’re gonna tell you it’s not burning properly when it’s that high, and you’ve got a problem, and we actually got our hands on the CO-testing standards for the gas company here in the Twin Cities, or one of them, Center Point Energy, and we’ve got their little cheat sheet that they give to their texts, and their threshold is 100 parts-per-million when they hit 100 parts-per-million.


RS: When it’s above that, they yellow tag the furnace and say it should be serviced. So we pretty much follow suit if it’s above 100 parts-per-million we recommend having the furnace serviced. We’re not saying, “Hey, you’re gonna die. This is life and death, get it fixed immediately.” But something’s not working right, it’s not burning properly when it’s that high, and there’s usually something, a heating contractor can do to lower that. So that’s our number. And if anybody wants that chart, this podcast is gonna be released at about the same time as a blog post that I’m doing on that topic, and I’ll share that chart on my blog post that that blog should be released on August 24th, I believe the day after this podcast goes live, so you can check out the blog and you can download that chart that we use if you’re interested.


BO: That’s great, very good. And then you can test without that equipment [laughter]


TM: You know, I was gonna ask you, Reuben, you’ve taught classes about this before, we’ve taught classes to real estate agents about this, but I think it’s an interesting thing to bring up, what happens when you’ve got someone who says, “Well, you know, I’ve had this furnace tested and certified already. And so your high CO reading must be wrong because my furnace is certified”, I run into that before on an inspection where a seller has fought me on that, where I’ve had a number that was above 100 parts-per-million and recommended to have it serviced and then they came back and said, “I just had it certified… You’re wrong.” What do you say about that? 


RS: I would question their equipment, just like we talked earlier about, who was last calibrated? Who’s is accurate. I would definitely question their equipment, we’ve had issues where our CO-monitors don’t register enough CO, but I don’t think we’ve ever had it go in the opposite direction where they registered too much CO, so I always question the low reading.


TM: And do all furnace certifications test the same things? 


RS: No, there is no standard for what a certification is in Minnesota.


BO: I mean I was gonna say…


RS: I mean, it’s all over the board.


BO: Yeah. What’s a certification? 


TM: Yeah.


RS: It’s whatever the contractor wants to call a certification…


TM: Right.


BO: You should get an HVAC stamp that says HVAC certified by inspector number 417 just like you get on your steak.


RS: Yeah, Right.


BO: Okay, is there any of these furnace types… We haven’t covered… We’ve gone through boilers. Oh, there’s one, there’s one. Reuben, we should talk about this really quickly before we put a wrap on the show, but there’s something we don’t test and we’ve been told not to test because you’ll always get the wrong answer. Do you remember what that is? Pop quiz from six years ago.


RS: It’s not… Oh, I got it Bill, I got it. Tessa, do you know what it is? 


TM: I think so, yeah… I think it’s a high efficiency, like an on-demand boiler…


RS: Yes, that’s where I was going.


TM: Yeah, we don’t test exhaust gases on those, so I’m picturing just those rectangular boxes that are mounted on the wall that have a PVC pipe that vents to the outside through the rim joists, those things. We do not test the exhaust gas on them.


RS: Is that what you were gonna say too, Bill? 


BO: Yeah, you guys nailed it. You were paying attention those years ago.


RS: Yeah, thank goodness. I didn’t think I was gonna get that, Bill, but it just came to me…


BO: Alright, so there it is, everybody, everything you need to know about testing carbon monoxide gas inside the vent of a furnace, no matter what type of furnace it is…


RS: Wait, wait, let’s correct. Not everything you need to know. Just everything we could think of. That’s probably a lot more.


BO: We are not authorities and we will not claim to be, we just happen to inspect a lot of houses, and so before we put a wrap on this, Reuben, can you just take a second and then explain why 400 parts per million is a problem when this is inside of a vent after all.


RS: Sure, and I’ll just, I know where you’re going with this, and I don’t know what’s so magic about the number 400, but the whole issue with having high CO, number one, if you have any problem with that furnace, where the CO leaks out and leaks out of the furnace, it leaks out of the vent or you have a failed heat exchanger and it leaks into the air stream, the higher the CO level, the greater you risk to have somebody die in their sleep, the greater risk you have of carbon monoxide poisoning. When the CO was really low, even if it were to back draft into the house, people probably aren’t gonna die, so that’s one part of it. The other part is that when the CO is too high, the furnaces isn’t burning properly, you have a much higher likelihood of soot accumulating on the burners and clogging everything up and make… Not operate properly. And number three, it’s not gonna be operated as efficiently and it’s gonna be cost you more to heat your house because you’re gonna have less fuel being used to heat your house and more unburnt gases just going up the flue. Carbon monoxide is the result of that.


BO: Right at the finish line, but it’s perfect ’cause you put a nice little bow on that, so…


RS: Perfect.


BO: Well, that’s it. I think we should put a wrap on today’s episode, it would be remiss of us today to not dedicate this episode and more to our good friend, Rick Norlin, who was the original owner, Reuben, of structure tech.


RS: Yeah, he was one of the co-founders of structure tech.


BO: Many years ago, and then Reuben’s pops bought it from him, and then Reuben bought it from his pops, but we lost Rick yesterday. Which is tough. It’s a tough day. So you’ve been listening to structure talk, a structure tech presentation. My name is Bill Oelrich, alongside Tessa Murry and Reuben Saltzman as always your three-legged stool in the Northland. Godspeed Rick, we’ll catch you next time.