Robin Jade Conde

PODCAST: Improving Indoor Air Quality (with Jeff May)

In this episode, Reuben Saltzman and Tessa interview Jeff May, an expert in indoor air quality and mold. They discuss various topics related to indoor air quality, including whole-house humidifiers, furnace filters, UV filters, standalone air purifiers, heat recovery ventilators, mini-split systems, and carpet cleaning. Jeff provides valuable insights and recommendations for improving indoor air quality and reducing allergens in homes. In this conversation, Jeff May discusses various aspects of indoor air quality and mold issues. He shares tips on cleaning and treating rugs, as well as testing indoor air quality. He also provides insights on finding qualified professionals and using homeowner testing kits. Jeff shares interesting and unusual cases related to indoor air quality, including the impact of sound and pressure. The conversation concludes with closing remarks and information on how to contact Jeff for more information.


  • Use trickle-type humidifiers to maintain proper humidity levels in the home.
  • Choose disposable filters with higher MERV ratings for better air filtration.
  • Avoid using electronic air filters and UV filters as they are less effective.
  • Consider using a DIY air purifier with a high-efficiency filter for targeted air filtration.
  • Regularly clean and maintain heat recovery ventilators to prevent mold growth.
  • Remove carpets or use steam vapor machines for effective carpet cleaning and allergen reduction. Regularly clean and treat rugs to remove dust and allergens.
  • Testing indoor air quality involves taking air samples and identifying the source of mold or other contaminants.
  • The Indoor Air Quality Association (IAQA) is a helpful resource for finding qualified professionals.
  • Homeowner testing kits are available for testing dust mite allergens, mold, and VOCs.
  • Indoor air quality issues can be caused by a variety of factors, including mold, VOCs, and particulate matter.
  • Unusual cases of indoor air quality issues can include vibrations from flooring and changes in air pressure.
  • Sound and pressure can have an impact on indoor air quality and human health.
  • Contact Jeff May at for more information on indoor air quality.


00:00 Introduction of Jeff May
03:49 Whole House Humidifiers
07:31 Furnace Filters
17:29 UV Filters
20:31 Standalone Air Purifiers
25:24 Heat Recovery Ventilators and Ventilation Strategies
29:13 Mini Split Systems and Mold Growth
33:11 Low Hanging Fruit for Improving Indoor Air Quality
36:56 Carpet Cleaning and Maintenance
37:57 Cleaning and Treating Rugs
40:02 Testing Indoor Air Quality
42:42 Finding Qualified Professionals
43:23 Homeowner Testing Kits
45:18 Identifying Indoor Air Quality Issues
46:38 Unusual Indoor Air Quality Cases
49:28 Effects of Sound and Pressure
51:09 Closing Remarks



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.


Reuben Saltzman: Welcome to my house. Welcome to the Structure Talk Podcast, a production of Structure Tech Home Inspections. My name is Reuben Saltzman, I’m your host alongside building science geek, Tessa Murray. We help home inspectors up their game through education, and we help homeowners to be better stewards of their houses. We’ve been keeping it real on this podcast since 2019, and we are also the number one home inspection podcast in the world, according to my mom. Welcome to another episode of the Structure Talk podcast. Tessa, wonderful to see you. We’ve got a special guest on today.

Tessa Murray: Oh, my gosh.

RS: I am super delighted ’cause we’ve got some good questions that we’ve had from the listeners about indoor air quality. We’ve had people sending in emails and it’s kind of been building up over the last year and I think we’ve got a fantastic expert to talk about a lot of this stuff. Tess, would you introduce Mr. May? Can you…

TM: I’m honored. First of all, we’re having on Jeff May today. For anybody who doesn’t know who Jeff May is, he’s one of the best in the industry when it comes to indoor air quality and mold. And I’m not only honored to have you on the show, but I am, honestly, I’m a little bit intimidated and nervous to be on the show with you, Jeff. But I’m really looking forward to diving in to talking about indoor air quality and mold things today with you because I know there’s a lot to learn and we’re learning from the best today. And just a little background, Jeff has a Bachelor’s from Columbia in Chemistry, a Master’s from Harvard in Organic Chemistry.

TM: And Jeff, you’ve been featured in several articles, New York Times, you’ve been on the news, you’ve been interviewed by Dan Rather, I believe I saw. You’ve spoken nationally at different conferences all over and you’re an author of several publications and lots of books, one of them being My House Is Killing Me. So we are so honored to have you on the show, Jeff. And please tell me if I got anything wrong in that introduction, and please tell us, too, we’d love to hear kind of how you got into this industry, the history, and what brought you to where you’re at today and to talk a little bit about your company that you have now.

Jeff May: Well, thanks, Tessa. That was all correct. It sounds great to me. I guess I had a lot of allergies, I had a son with asthma, and he was hospitalized. And then we tried to sort of figure out what might be wrong, and I got curious looking into the environment and discovered that he had severe dust mite infestation in his bed. So, and I took some classes at Harvard on indoor air quality and then that was while I was doing home inspections. So I learned a lot about houses, and then I was kind of off and running. I’ve taken a lot of classes from some pretty well known people in the industry. And what’s different about what I do is I look at all of my own samples. I’ve done about 35000, 40000 samples now over the years, and I look for things that really the labs don’t look for. So I get a lot of information from slides that other people don’t.

RS: Wow, wow.

TM: There’s a million questions I want to dive into about that, but we’ll get to that, I think. We’ve got a list of questions, Reuben and I kind of discussed before we had you on the show what we wanted to ask you while we were here. And we want it to be helpful and relevant to our listeners. Majority of them are home inspectors, but we also have people from all over the country that tune-in and listen that just want to learn more about houses and how to maintain them, how to improve them. So some of those questions are going to be a little bit more technical, but some of them, hopefully, are going to be bigger picture, too. But, Reuben, do you want to kick it off? 

RS: I’d love to. Thank you, Tess.

TM: Okay.

RS: So, kind of the theme here is what you can do to improve your indoor air quality. And number one, I want to ask you about whole house humidifiers, and I don’t want to steer the conversation in any direction. What’s your take on those? Good, bad, indifferent? What do you say about a whole house humidifier, Jeff? 

JM: So you mean a humidifier on the furnace that adds moisture to the air, correct? 

RS: That’s right.

TM: Yeah.

JM: Okay. So years ago, the simple devices that they had were really terrible. They created enormous air quality problems. So there are a lot of people who can’t stand that sort of very dry, hot air in the winter. And so the safest type of humidifier to use is the one that, it’s a trickle type. So there’s a little sort of aluminum mesh and water trickles down, and air from the furnace goes over that, evaporates some moisture. And I guess the caveat is you don’t want to let the moisture in the house get over 40%. In very cold weather, you may have to even keep it lower at 30%. But if you get a lot of condensation on windows, then that’s a problem. But having too dry conditions contributes to health, respiratory problems. So you don’t want it really dry.

RS: Okay.

TM: Is that threshold for really dry, would you say that’s about 20% or 25% relative humidity? 

JM: Well, 20% or lower, yeah.

TM: Okay. Yeah. So you’re saying in a colder climate, keep it somewhere between 20 to 40, just depending on how cold it is? 

JM: Well no, higher than that. I mean, above 30, but not much over 40.

TM: Okay. Yeah.

RS: Okay. Got it.

JM: It really depends on the weather. If it’s really cold out, you can’t go that high ’cause you get a lot of condensation.

TM: Yeah.

RS: Sure.

TM: So those systems, those humidifiers that you’re describing, we see those all the time here in Minnesota. So many houses have those. And a lot of times if you take the cover off and you look at that little mesh screen, it’s green, it’s nasty looking. Is that the source of the indoor air quality concerns that you have, or is it something else? 

JM: Well, I mean, the trickle type with this screen, they don’t usually get too dirty unless you have bad filtration. I mean, if you have a decent filter on a system, I think they’ll be okay. But if you change the filter every year, that should be fine. But the old kind with the rotating drum ones, those were lethal. I mean, they basically had a puddle of water and then the dust would go into the water and then the drum would rotate and the drum would be covered with mold and then the air would blow over that. So those type, I don’t think they make them anymore.

RS: No, no, I don’t think so.

JM: But the steam type also, those are also… The steam are the sort of Cadillac of the industry. But again, they have to really be, when any kind of, in humidification system you’re putting water in and you really have to monitor these things. The problems come in when nobody ever checks anything.

RS: Okay. Now, you talk about filtration of the air and that kind of brings us to the next thing I wanted to ask you about is furnace filters. Where do you stand on that? I mean, do you recommend the cheap little 99 cent ones, the more expensive $20 ones with the super high MERV rating? What do you think about electronic air filters? What would you recommend for someone who’s got asthma or allergies? What would you say? 

JM: Well, the best type of a filter is a throwaway. The electronic ones, they may run for a couple of weeks and as soon as they get any kind of dust on the wires, they cease to function. So I’ve never seen a functioning electronic air filter. They do work in the industry where they get cleaned very, very frequently. But the best type is the disposable filter, and the higher the MERV rating, the better. So a one inch filter, you can’t have too high a MERV rating because it cuts down on the airflow. So the best type are these four or five inch deep pleated media filters. And the ASHRAE, American Society of Heating, Refrigeration And Engineers, they say that if you have air conditioning, you shouldn’t use anything less than a MERV 8 filter. But for people with allergies, MERV 11 or 13 is the way to go, so long as it doesn’t cause too much reduction in airflow.

RS: Okay. All right, so you’re not a fan of those electronic filters. What if you did have a really diligent homeowner? Every three weeks, they take out their pre-filters, they wash them, they take out the cells. I don’t know anyone who does it every three weeks, but you take out the whole cells and you wash them down, or you put them in the dishwasher or whatever, you clean the heck out of them. In those cases, could it be a viable alternative? 

JM: I think most people, given the lack of maintenance and time, people, it’s just, it’s not feasible. The only thing, the disposal… And the people who have electronic filters, they do make, a lot of the manufacturers make a pleated media filter that just replaces all that electronic stuff.

RS: Sure.

TM: So it’s easy to convert. Yeah.

JM: And the washable ones, I don’t like either. The washable, people get these washable electrostatic filters and you can never get all the dust out of those, so you really, the best way to go is disposable filter.

RS: Okay, got it. And when you say that there’s a replaceable media to go in there, I just want to make this clear for anyone who’s not following along, and correct me if I’m wrong, Jeff, but you’re saying that if you have, let’s say you buy a house and it already has an electronic filter system, typically that’s going to be a four inch opening, and you can remove the electronic cells, you can remove the pre-filters, and then you can just install a replaceable four inch furnace filter in that opening so you get really good filtration. You don’t need to get an HVAC contractor to come in and tear things up, tear apart your ductwork and put it all back together, you can use that existing opening. Is that what you’re getting at? 

JM: Absolutely. Yep. You just have to make sure that it fits airtight. A big problem with good filtration is that there’s bypass around the filter, and that’s like a condom with a hole in it. You just, you really, you want to… And the thing is filtration is really important for people who have central air conditioning. I mean, with furnaces, it’s important, but with, for central air, it’s critical. And I actually, I did a study in the Boston area where I compared 300 houses, control houses that I had looked at for home inspection to 600 houses where people were actually sick.

JM: And what I found was that 19% of the homes in the Boston area have central air conditioning. It’s kind of low because it’s an old city, and 38% of the houses where people were sick had central air conditioning. So you get from that you’re twice as likely to be sick if you have central air. And, of course, why is that? It’s because you’ve got all the mold growing on the coil and then the pans and things. And why is that? Because you don’t have adequate filtration. So, really, the key to having a healthy indoor air quality is to have a good pleated media filter.

RS: Okay.

TM: That’s a really interesting study, Jeff. And I’m curious, do you think some of that has to do with, the results have to do with people that live with their windows open versus people that live with their windows closed? ‘Cause if you’ve got forced air AC, you’re keeping your house shut up in the winter. And so do you think some of those health issues could be coming from other things in the indoor air environment? 

JM: Well, it’s possible, but just having looked at thousands of pieces of air conditioning equipment and 90 plus percent of them are full of mold. And I guess it’s just that not that many people are allergic to mold. And so therefore these conditions within these systems remain that way because not enough people get sick. But I think as time goes on, like right now, 100% of new construction is with central air. So we’re getting big, big increase in amounts of central air and so more people will be sensitized.

TM: What do you recommend then, Jeff, for people that have forced their air conditioners and have these A-coils that are covered in mold in these systems? How do you fix that problem? 

JM: Well, the coils can be cleaned. And the sad thing about this whole, I don’t know what the scenario is that, people always talk about duct cleaning, and ducts can be dirty, ducts can be contaminated but the real source of air quality problems, in my opinion, is from the air conditioning coil. And NADCA, which is the National Duct Cleaner Association, they surveyed their members a few years ago and only 40% of them would even clean an air conditioning coil. So most people don’t ever get the coil cleaned, they just have the ducts cleaned. And so that doesn’t really help them in terms of air quality.

TM: It’s not addressing the problem. Yeah. And I’ve never, I’m not aware of any contractors that offer that service. Are you, Reuben? 

RS: No, no. And I was just going to ask how it even gets cleaned. What is the process? Do you know? 

JM: Yeah. Well, what’s interesting, I think one of the duct cleaners said that they don’t clean the coil because they get a lot of their referrals from the HVAC people, the installers. And if they start cleaning the coils, they won’t get the referrals. So that was one excuse. But I think really the bottom line is that it takes a lot of effort to clean a coil. First of all, you have to remove the access panel. A lot of times it’s blocked by the venting. It’s difficult to access, and they rinse it through, typically they’ll use some chemicals that they, detergent kind of chemicals that they’ll push through. And they, you can also use steam.

JM: There’s one company that uses high pressure steam to clean the coils, but there are not a lot of companies out there that will do it because you can’t make money. The way they, a lot of these companies, they’re what they call blow and go companies, they just have a big vacuum truck in the street and then they just suck it for a few minutes and they pull some dust out and they show the homeowner but you have to use brushes. But if you’re doing one of those blow and go jobs, it’s a couple of hours, you get whatever, 800 or 1,000 bucks or something. And if you’re cleaning a coil, that could take two or three hours just to open it up, access everything, clean it.

TM: Wow.

RS: Yeah.

JM: So it’s very time consuming work, labor intensive, and so they don’t make money on it. So they don’t do it.

TM: Wow.

RS: Okay, that makes perfect sense. All right.

TM: Yeah. Just going back to the duct cleaning thing, so, Jeff, would you say, in general, you wouldn’t recommend duct cleaning as a solution to resolving people’s indoor air quality problems? 

JM: No, I think duct cleaning can be very important because there are a lot of allergens that will be in the ducts and that will… So if you have like a dog allergy or a cat allergy, then you can, it’s in the ducts and you’ll have that problem. I actually looked at a house, a new construction, and the guy was allergic to ducts. And I said, look, you have tons of dog dander in your house here. And he said that’s impossible. It turns out the builder brought his dog every day to the, on site, and he contaminated the whole house with dog dander. So I think it’s important to clean the ducts. Where most of the dust is, is on the return side. So I always recommend people put a very coarse pre-filter on the return, and that will increase the lifetime of the pleated media filter tremendously because most of the dust that accumulates is skin scales and pet dander and lint from carpets and laundry.

RS: All right. I want to move on for time’s sake, but I have to stop and just ask you about this coarse filter. What would that look like? 

JM: It’s like a fiberglass filter. You can buy material, you can see through it. If it’s, a coarse filter is a material you can see through.

RS: So maybe back in the day, you had these big basket filters on the first generation of forced air furnaces where you’d buy a roll of fiberglass material, you’d buy like a 10 foot roll of it and you just cut it to size and fit it into your basket. Is that kind of what you’re thinking of, where you just cut a piece and you fit it in there? 

JM: Yep.

RS: Okay. All right. Got it. I’m tracking. Sounds good. Now, more on just having a nasty environment in your furnace and your AC. What about using UV filters? Where do you come down on that? 

JM: I’m glad you asked about that, because with COVID, these companies were selling all kinds of gadgets and even if you go on the Trane website, they do the calculations. So in order to kill anything in an air-stream, you need a certain kill time. And they estimate you need a UV lamp that’s 400 feet long in order to kill spores in an air-stream.

TM: What? 

JM: So that’s completely useless now. For years, people used UV lamps in schools, in hospitals, they would be at the ceiling and shielded from the floor. And now you have particles that are traveling by convection very slowly over the UV lamp. And that’s certainly effective, that’s been shown many, for years and years to be effective. But in a system, you can’t disinfect the air. The other way they sell these UV lamps is to irradiate the coil, and it supposedly kills things on the coil. So commercially when they do that, they have five lamps, the entire width of the coil if it’s a vertical coil. And so the entire surface is irradiated. And that radiation, if you put your hand in there, you’ll be severely burned.

TM: Wow.

JM: So that kills everything. But these little dinky tubes that they use for… To radiate the coil, they don’t provide enough radiation. The incident light at an angle is not effective. So most of the debris on the surface is gonna be in a shadow. So UV lamps don’t work. The only thing, again, always most important is good filtration. You don’t want to get particles onto the cooling coil.

RS: Okay.

TM: So what I hear you saying, Jeff, is that the commercial world has figured this out and it’s effective this UV light system, but it hasn’t transferred over to residential applications effectively yet.

JM: Yeah, I think because… Well, see, the coil commercially, I think, they’re mostly flat plate coils, and that’s pretty easy to set up the… But the A coils, it’s not easy to set that up. And I don’t think people would be willing to pay the money that it would cost to really set the thing up properly.

TM: Wow. Okay. So you would say you’re not…

JM: But there’s no reason to have dust on the coil if you have a good filter.

TM: Yeah. Okay. So focus on the filter side and you would probably not recommend a homeowner install a UV light system in their duct work? 

JM: Never. Never. They’re useless and they actually put… I’ve been in places where they, I could smell ozone that was from the lamp. [chuckle]

TM: Wow. Which is toxic, right? 

JM: Because the UV produces ozone. Yeah.

TM: Yeah.

RS: All right. Well, we got a show, we’re good. I don’t need anymore.


TM: Mythbuster, yeah.

RS: But that’s great. Thank you. And no, we got a bunch more to run by you while we got you, Jeff.

JM: Sure.

RS: I want to ask you about standalone air purifiers. What do you think about those? 

JM: They work, they’re great. I actually set it up in my office one time with a particle counter, and the particle count dropped to nothing, but as soon as you get up and walk around, the particle count shoots right up again. And my best example for that of how it isn’t that helpful is if you are allergic to dust mites, you’ve got all that allergen in your mattress. If you put a thousand dollar air filter in every corner of the bedroom, once you get into bed, you’re gonna still be exposed to that allergen.

JM: And so you always wanna solve the source problem first and then go to the air purifier. They work great. And actually, there’s one manufacturer now that makes something that’ll just blow HEPA filtered air into your face so it doesn’t filter the whole room, it’s just filtering the air that you breathe. And that can be very helpful. Plus there’s this thing called the Corsi-Rosenthal filter. I don’t know if you heard of that? 

RS: No.

TM: No.

JM: Well, this is great. It’s two researchers who I think they figured this out. You just, you need a 24 inch window fan and…

TM: Like a box fan? 

JM: And you make a box for the fan with MERV 13 filters, it’s all put together with tape. It costs about $100, and it’s as effective as an $800, $1000 fan. You have a bottom and then the sides are all MERV filters, and the fan is sitting horizontally on top of the filters. It’s all taped together. And there are a lot of schools that are using them. And the difference is that if you buy one of these really expensive HEPA filters, maybe they’re like 300 cubic feet of air per minute, but this Corsi-Rosenthal thing does 1700 cubic feet of air per minute. So, and it’s very, there’s been some papers written about it. It’s very effective.

RS: I’m on Wikipedia looking at it right now.

JM: Okay. Yeah.

RS: Yeah, it’s exactly what you described. It’s a bunch of filters duct taped together.

JM: Right. Yep.

RS: With a box fan sitting on top of it.

TM: Wow.

JM: It’s miraculous.

RS: Wow. Okay.

JM: It’s ingenious.

TM: What’s it called again? 

RS: Corsi-Rosenthal fan filter box. Yeah.

JM: Yeah. Filter box. Yeah.

RS: Okay.

JM: C-O-R-S-I-Rosenthal.

TM: Interesting. And this is something that a homeowner could create and install and they install it in a…

JM: Oh, yeah, anybody. Absolutely. Oh, yeah. I have… Yeah, one of my clients has two of them in his little apartment.

RS: Okay. So if you want a good whole house filter, not whole house, but a good room air purifier…

TM: Make your own.

RS: Make one of these. Okay.

TM: Jeff, I think you just gave Reuben his next blog topic.


RS: I love it.

TM: We were gonna be seeing a homemade Reuben Saltzman filter soon.

RS: I might make one of these. Yeah. So good.

JM: I’ve been tempted. It’s funny, I’ve been tempted, but I couldn’t find the filters.

TM: Huh.

RS: Okay. Wow.

TM: Are the filters hard to find for it? 

JM: Well, I think you can get them online. It’s just Home Depot didn’t have the right… They didn’t have the filter size.

TM: Got you. Okay. Going back to these air purifier systems, if someone doesn’t have the materials, the time or the ability to build something like this, are there certain, I guess, qualities you’d look for when you’re buying an air purifier? 

JM: I think what’s important to people is the level of noise and then how much air it’s actually filtering. But there are so many of them. I think some of them are, the less expensive ones work fine. You don’t have to spend $800 for it. You can get a decent one for 300, I think.

TM: For 300? And it would be, would you say get a HEPA air purifier or? 

JM: Yeah, it’s HEPA. Yeah.

TM: Okay.

RS: All right. Now, let’s talk about another device that’s constantly bringing air in and out of the house. At least we’ve got a ton of these in Minnesota, and it’s your air exchanger more technically known as a heat recovery ventilator or an energy recovery ventilator. What do you think about those, and what do you think about comparing one of these to some other type of ventilation strategy such as exhaust only ventilation? Here in Minnesota, that used to be pretty common, where you’d have a fan running all the time, constantly pulling air out of your house. What do you think about all these different things as they relate to indoor air quality? 

JM: Well, I think that an HRV, they’re called, they can be very effective in bringing in fresh air. But I guess the issue I have with all of these things is that everyone that I’ve looked at had a big mold problem. Because if you run it continuously in the summer, you’re pulling in all kinds of pollen and bugs and things, and they get full of that stuff. And then you can have condensation in the winter if it’s cold or you have high humidity in the summer and so these things get full of mold. And none of the machines have adequate filtration. They have these very small filters, they’re not attached properly. There’s bypass around the filter.

JM: So I always recommend that people use supplemental filtration, and you can buy an inline filter box with a… It comes with a MERV 12 filter, but it’s a, Fantech makes an FB6 filter box, and you switch that out with a MERV 8 filter and that filter, I forget, I just, it’s a 20 inches long and maybe 12 inches wide. So it’s about four or five times the, maybe even 10 times the surface area of the filter that comes with the unit. And maintenance is very important. You have to clean the heat exchange coil. I think most people just set them up and then like everything else, they just, they never think about it again.

TM: So true. Yeah. I mean, when I was inspecting houses every day, it was, yeah, every time we came across an HRV or ERV, you open it up and usually you’re bombarded by dead bugs and dust falling on you, but it’s like no one has ever opened it and cleaned it and didn’t even know that there were filters.

JM: That’s right. Yeah, in fact, I had one family where when I inspect, they were all sick with algae problems and when I inspected it, it had been there for nine years. I put the plug back in, it didn’t turn back on again. And that was on a Friday, and I called them on Monday. It was the first time they had no allergy problems anymore.

TM: Wow.

JM: It was, the HRV stopped working.

TM: Wow. Now, I’m trying to picture this inline fan you’re talking about. How does it get installed? Is it installed on the, like the intake side, like in the duct that connects to the HRV from the exterior air intake? 

JM: Yeah. Right. You can do both. See, most of the dust that gets into a unit like that, it comes from the outdoors or it comes from the indoor intake. So I usually recommend two of them, and you just… It’s a box that has openings for ducts. It’s a six inch opening for… You just attach the duct to each end and that just filters the air before it gets into the HRV. But again, that’s something that has to be maintained. If you’re running it continuously, you can imagine the junk that gets sucked in there in the summertime.

RS: So when I think about an exhaust only ventilation strategy for a home where you’ve got one of those Panasonic fans up in the primary bathroom…

TM: Hallway.

RS: Or in the upper hallway, and it runs at 40 CFM nonstop, we know that the air coming in is gonna be unfiltered outdoor air leaking through openings in the holes, exterior or coming in through the combustion air duct, which might double as a makeup air duct. And there is no filter on that. You’ve got a quarter inch grill on the outside. What do you think about putting a filter on there? And I say this ’cause now you’re filtering what could be the combustion air intake and you know how nasty those things get when you have a quarter inch screen. I can only imagine how fast it’d get clogged if you had a filter. What do you do? 

JM: Yeah. I don’t… I’m not sort of familiar with that exhaust only system. I don’t think I’ve seen it. It’s sort of wasteful. I guess the reason they come up with the HRV is to get around that, to sort of do some heat exchange.

RS: It is.

JM: And there are companies now that are making smaller units. I haven’t seen any of those yet. But they just, like a room-sized HRV, it goes into the wall and there’s two, I think there’s two units. One air comes in and one air goes out.

RS: Yep. Okay.

TM: Would you say that… I think we’re gonna be seeing more and more heat pumps and mini split systems in houses. And do those have issues as well with mold growing inside on the coils? 

JM: Yeah. Oh, for sure.

TM: Okay.

JM: In fact, when… The mini splits have to have this really high seasonal energy efficiency ratio. So what the manufacturers did is they reduce the power of the blower so that you cannot put a filter on a mini split. You just can’t, because it won’t draw any air. And so they have this little insect screen and it’s useless. So what… The dust builds up on the blower blades and on the exterior, and honestly, just about every mini split that I’ve looked at had a mold problem. And the only ones that don’t is when they’ve only operated in the heating mode, they don’t use it in the cooling mode. But as soon as you use cooling, you have moisture condensation, and then you got dust. And just open the louver up and I look inside and there are all these little black spots everywhere.

RS: Well, I was a huge fan of mini splits until just now, Jeff.


JM: Well, they’re great but they get dirty. If you look, go on YouTube and just Google cleaning a mini split, and you just, you won’t believe the garbage that comes out of these things.

TM: And it is possible to clean them. It’s easier, it sounds like, or I think than like an A-Coil for forced air AC system, is that? And there’s ways that you can do it yourself or you can hire a professional to do it.

JM: Yeah, there are a lot of videos now. And what they’ll do is, well, in the beginning there was no way to clean them. It was ridiculous. Now, they put a big plastic bag underneath the bottom and then they just rinse everything with detergent, and all the muck goes into the plastic bag. So they can be cleaned but the irony is that people are buying these things ’cause they’re saving money on energy, it’s high efficiency. But in the end, like, let’s say you’ve got four mini splits that you use, you’re gonna have to spend a couple hundred dollars every other year. So you’re spending money on cleaning it instead of energy.

TM: The maintenance of it. Yeah. Yep.

RS: Sure.

TM: Interesting.

RS: Few other questions for you. Another one is, if someone does have indoor air quality issues, besides all the stuff we’ve talked about, what is some low hanging fruit that people should go after? What’s some of the biggest problems you see in people’s houses that they’re just, it’s like a no brainer, like, “Hey, get rid of this source.”? 

JM: Dust is the devil. [chuckle]

RS: Dust. Okay.

TM: Dust. Okay.

JM: Dust is the devil. Yeah, really, just have some fresh air and get rid of the dust. I’ve taken, as I said, like thousands of samples from dust and there’s just all kinds of evil in the dust. So you clean under things and behind things. Another big problem, refrigerators, people don’t ever clean the coil for the refrigerator… Not the coil, but the drip pan. And those things get full of mold.

RS: Okay.

JM: So that’s a pretty low hanging fruit.

TM: That reminds me…

JM: We’ve had clients, just cleaned their refrigerator, the coil or drip pan and all of their allergies went away.

TM: You know that as we’re talking about this, this reminds me of something that Mark Pierce, you know Mark Pierce, Jeff? 

JM: Sure.

TM: One of…

JM: He’s out your way, right? 

RS: Yeah.

TM: Yes. I believe he passed away recently.

JM: Oh, really? 

TM: Yeah. But he… For anyone that doesn’t know Mark Pierce, he was one of the most interesting, fascinating people to listen to. But he was a mold expert, indoor air quality specialist as well. And I remember him saying like, the first thing to do is instead of throwing all this money at fancy filtration systems and filters and ozone and lights, whatever people are doing, he is like, “Get rid of your carpet, carpet brings dust and mold and nasty stuff. Just get rid of it.”

JM: That’s right. Yeah, for sure. Yeah. That was on my list, actually. I’ve done this calculation, it’s pretty simple, but if you just, let’s say you have one square foot of oak floor, solid floor. Now, you put one square foot of carpet, you now have 70 square feet of area because of all of the fibers. And so that’s how you get that huge reservoir for dust. And when you take samples… If you take a room air sample and there’d be 3000 particles per cubic foot, and then you bang the carpet and it goes up to 100,000. So at least for people with allergies, getting rid of carpet is about one of the best things they can do.

RS: Okay. All right.

JM: And I’ll tell you another suggestion. I always tell people if they don’t wanna remove the carpet ’cause that can be a costly thing, you can, there’s a plastic film that painters use to, when they paint on carpets, it’s called Carpet Protector. And you can buy it online, you can get it in Home Depot. And I’ll say, look, if you don’t want to get rid of the carpet, just cover the carpet where you walk, and then you won’t be breathing in any more of that aerosol. Now, if you feel better, then it’s not a bad idea to get rid of the carpet. So it’s a diagnostic thing, especially on stairways. When you go up and down stairs, you create a lot of aerosols, so you just put the plastic down and that can make a huge difference. In fact, with all my allergies, whenever I stay in a hotel, I always bring carpet protector with me.

TM: Do you? 

RS: Interesting.

JM: Yeah, I have to. I’ve been in… I took an infrared class in Burlington, I think it was, and I couldn’t breathe in the hotel room. And I just put the plastic down where we walk, from the bed to the bathroom and the desk and I was fine for a week.

TM: Wow.

RS: That’s great.

TM: Amazing.

RS: Now, what about cleaning your carpet? Is there like some type of industrial shampoo or some type of carpet cleaning process you’d recommend that’s gonna make it a lot better? 

JM: Yeah, absolutely. Lots of times people will clean their carpets, the carpets stay wet too long and then just becomes a little forest of mold. So what I always recommend is using steam vapor. These are machines that you can buy, steam vapor machine, and it looks like a little canister vacuum cleaner, but it boils water. And the steam comes out, it’s 40 pounds of pressure. And at that temperature, if you go over your carpet, you will kill every flea, every dust mite, every bug, everything instantaneously. And if you go over slowly enough, it’ll destroy all of the allergens. Many allergens are very sensitive to heat, and so the steam actually destroys the allergens. So the steam vapor machines, you can get one for about $300 or $400 and they’re really miraculous.

RS: Okay.

TM: Wow. And you don’t need chemicals or detergents or anything like that? 

JM: Nothing, just steam. Yeah. You vacuum thoroughly and then just hit steam.

TM: How often would…

JM: For rugs you can actually… When you vacuum, you can never really remove all the dust. It’s like you vacuum a hundred times, maybe you’ll get 70% of the dust out. So, but if it’s a rug, you can hang it up and then blast it with air from a leaf blower and that’ll get rid of a lot of the dust. And then you treat it, it’s hanging up with steam vapor and that’ll kill anything.

RS: Okay.

TM: Did you say leaf blower? 

RS: He did.

JM: Yeah. Leaf blower. You want to blow the dust out, you blow it from the back.

TM: We actually know someone who uses a leaf blower to move dust around, don’t we, Reuben? 


JM: What? 

RS: It’s an inside joke about my wife. Sometimes when I’m gone, she will bring this little battery powered leaf blower inside to blow all the dog hair to one side of the house. That’s an inside joke.


JM: Yeah. Oh, it’s… No, but I’ll tell you, there’s actually, there’s a process called the dust down and they use a leaf blower to get rid of dust. Like when you have a lot of trinkets and all kinds of stuff and you can never dust in a room, you just put an exhaust fan in the window and you use a leaf blower. You just have to wear a face shield because you don’t wanna get a pencil in your cheek. But you…

RS: So if my wife would put a box fan in the window, then she might be able to do this while I’m home.

JM: An exhaust.

RS: Huh? What were you saying? 

TM: Creates an…

RS: ‘Cause I’ve never seen it done. I’ve just heard rumors about this.

JM: Oh yeah, no, it’s done. It’s actually, it’s a legitimate way of getting rid of dust.

RS: Well, I don’t know if I’m gonna let her listen to this podcast, we might have to bury this one.


TM: Oh, given her ideas.

RS: So, all right, Jeff, moving on. If somebody does have some indoor air quality issues that they’re concerned about, they think, “My house is killing me, I don’t know what’s going on,” as home inspectors we’ll go in and we’ll check all the obvious stuff. I mean, we’ll look at their combustion appliances, bath fans, clothes, dryers, properly venting to the outside, check all those big boxes. But besides that, what could someone who specializes in this do? What type of tests would you do for someone who’s complaining about problems? It sounds like you’ve done a ton of testing.

JM: Typically, I will take air samples because I wanna know what people are breathing, what they’re exposed to. And look, a lot of these mold inspectors, they’ll just take a couple of air samples and say, “Oh, you got X, Y, Z in the air,” but they don’t know where it’s coming from. So the key to this business is determining the source of the mold. So I mean, I had a situation and I’ve seen other people where you had, let’s say you have an exhaust fan for a bathroom on the first floor and you have the stack effect, you’re sucking in air through the vent. And the duct can be… The exhaust pipe can be full of mold and it’s sucking it in because the air is leaking out of the house. I’ve checked in my house, we have a fairly tight house and most of the fresh air comes from the dryer duct.

RS: Oh, wow.

TM: Wow.

JM: Everything’s closed up and the one opening to the outside is the dryer.

RS: Sure.

TM: If you don’t have a damper that’s closing or working properly, I guess, air’s leaking.

JM: Which never… Have you ever seen one that closed? I don’t think I have.

TM: That’s a good point.

JM: And I clean mine all the time, still stays open.

TM: And to that point, yeah, and actually, just the other day I was taking laundry… Or I opened up the dryer for something and it was really cold inside the dryer. Like there’s a lot of fresh air from the exterior.

JM: Yeah, there’s infiltration. So if you’ve got a moldy duct, then that can be bringing in problems. So you wanna… So getting back to the original thing, I guess… We’ve had people just get rid of one rug and all of their allergies went away, or one quilt, one pillow. So I sample all of these things. I sample couches, I just, I bang it with a… Actually, I use a spatula, I bang it and then I collect the dust that comes out, and then I just look at it. And that’s how you figure out where the sources are. Anything cushioned can be a source or a duct.

RS: So if someone was trying to hire someone like you, I mean, you’re in New England, right? So if someone, say, here in Minnesota was looking for someone with your type of qualifications, what would they look for? 

JM: I think the Indoor Air Quality Association has a list. It’s called IAQA and they have a list where you can find some local people that do that kind of work.

RS: Okay. All right.

TM: IAQA. That’s a helpful resource. Because as I’ve gone into the consulting kind of world myself, and I’m dealing with homeowners and clients who have concerns about indoor air quality, just trying to find someone who has… Offers a variety of services that cannot only test for just mold, but also does things like find particulate matter, VOCs or rate on it and does it all, it’s hard to find that because a lot of companies I find advertise themselves as indoor air quality companies, but all they do is test for mold. And I know there’s so many other potentially harmful things out there that are impacting people’s health.

JM: Right. Well, there there are actually, there are some companies that sell sort of like homeowner kits. So for example, you can test for dust mite allergen, you get a little vacuum cassette and you can vacuum that up. You can do that for mold as well. And there are companies that sell… They’ll rent you a little pump and you can take your own VOC sample. So there are a lot of things that homeowners can do if they have a little bit of confidence that they can do it themselves.

RS: So you feel those are legitimate? 

JM: Yeah. Oh yeah, sure.

RS: Okay.

TM: Where would you find a kit like that? 

JM: There’s a company in Florida that does a lot of that. I can’t think of the name right now but it’s very legit.

TM: And they’re pretty affordable? How much would it cost for one of these kits? 

JM: Oh, they’re not that expensive at all. No.

TM: Like under 100 bucks? 

JM: For the allergen tests, yes. But for the VOC, it’s a little more expensive. But I mean, I think even for $200 you can get what… What I use and what other professionals use are little charcoal tubes. You suck air in and then you have to send that tube in and they analyze the gases in the tubes so you can actually get the tubes, buy them and get a kit or get the pump and then send the whole thing back to the company.

TM: Okay. Would you say that the primary concern that you find though, or the primary issue that you find in homes that you’re testing is mold or sometimes is it VOCs or other fine particulates? 

JM: Oh, it can be just about anything. I don’t do that much. I mean, I have a particle counter, I don’t do much with VOCs, but I’ll tell you just a very interesting VOC story. This woman was getting sick in her house and I found a very high concentration of all different kinds of fragrances in the air in the house. And she said, “It’s impossible. I don’t use any fragrances at all.” Well, it turned out she started getting sick after they put a vapor barrier in the crawl space. The vapor barrier was made from recycled shampoo bottles and the whole house was full of fragrances from shampoo.

TM: You’re kidding.

RS: Woah. Holy cow.

JM: And the company came and replaced it. The company came and replaced the vapor barrier.

RS: Our jaws are on the floor here.

TM: Yeah. You can’t see our face because this is a podcast, like my mouth is open. I never thought about the impact of potentially putting a vapor barrier down and how that could negatively impact indoor air quality. In my mind, I’ve always only thought that that would be a good thing because you’re preventing moisture and mold from coming in.

JM: Yeah. Well, I think it was unusual. It was just that company was using recycled…

TM: Well, and some people are so sensitive too to things.

JM: Yeah, sure.

TM: That is…

RS: Yeah. And to trace that down, that’s fantastic.

TM: Oh, my gosh. Yeah. I suppose a big part of what you’re doing is not only just offering the tests and the results of, “Okay, here’s the types of mold we found,” but you’re trying to figure out where it’s coming from, which is I think what’s unique and sets you apart from other indoor air quality companies. And a lot of that has to do with just investigating, asking people, “Okay, well what’s changed? Has anything changed?” And putting the pieces together.

JM: Well, the strangest thing we ever had was this guy that… This fellow said that he was… Had a new house, he had just moved in and he had been in the house for the first three weeks and he was fine. And then in the last week he hadn’t slept at all at night, his right lung was vibrating. And when I get these calls, sometimes I think, “Well, gee, do I even want to get involved in something that’s so crazy?” And I thought, “All right, I’ll give him a chance.” So I go out there and he hadn’t slept in a week. He was, you get sleep deprived, he was maniac.

JM: And finally I say, “Look, what happened a week ago? What was the change?” And he said, “Well, I put a floor down in the attic.” So we went up to the attic and they had installed this beautiful tongue and groove, diagonally installed big thick oak floor. And, or I don’t know if it was oak, but it was big. It was inched, very thick tongue and groove. And I was standing still and he was walking around and every time he took a step, I could feel his footstep vibrating. And it was what they call a damped harmonic oscillator. It’s like when you jump off a diving board and it kind of like, it slows down like that, it goes fast and slow. And so it suddenly hit me. What happened was when they put that floor down, they created basically a membrane, like a drum membrane in the attic.

JM: So when the wind blows, very well ventilated attic, when the wind blew over the ventilation system, it would either reduce or increase the air pressure in the attic and that would lift the floor and push it down. And so the floor would vibrate, the master bedroom was directly under the attic, and the air pressure changes in the bedroom were causing his right lung to vibrate. So I said, look, he hadn’t unpacked his books yet. And I, well, I stood, first of all, I stood on the floor and I would like very gently shake the floor and he would say yes or no while he was in bed. And he could tell 70% of the time, he knew when I was moving in the attic. So I said, “Just place… Take all your books and unpack the boxes, put the unpacked books on top of the floor in the attic.”

TM: Wind it down.

JM: And it changed the resonance… The frequency, and that solved the problem.

RS: Holy God.

TM: Unbelievable. Unbelievable.

JM: Nuts. Yeah.

RS: What other stories do you have, Jeff? I wanna get one more. Come on.


JM: I’ve got… Okay.

TM: One more, come on.

JM: Well, I actually got a… Here’s an interesting one. Sometimes, if you have like blowers that produce sounds, you can get like beats. You know when you have two notes that are close together and you get musical beats? So there’s… That causes changes in the pressure. And in bigger buildings people can actually be disoriented by that. And that actually happened to me. I was in a parking garage and I was walking through the parking garage and I started feeling very dizzy. And what I realized that there was an exhaust fan for carbon monoxide that was running and it wasn’t balanced. So the fan was oscillating in and out and it was changing the air pressure. And it made me dizzy.

TM: You know, so here’s a scenario. I wonder if it’s similar. Like if you’re driving a car and someone in the backseat rolls their window way down, all of a sudden you feel this weird vibration kind of pressure in your head and it’s like, ah, crazy.

RS: I was just thinking that, Tess, yes.

TM: “Roll your window up.”

JM: Yeah, my car does that too. It drives me crazy. If you roll the back window down, yeah.

TM: Huh, fascinating.

JM: Any changes, you know.

TM: That is so fascinating. Oh my gosh, Jeff, we could just, we could sit here all day and listen to your stories, couldn’t we Reuben? 

RS: Yeah. Well, we’re up against the clock. I promised you how much time we’d take up. I don’t want to take up any more, but man, this has been fantastic.

JM: It was great talking to you. I enjoyed it.

TM: Jeff, thank you so much.

RS: Yeah, we really appreciate it.

TM: Yeah, thanks for coming on the show.

RS: I hope we get to have you on in another year or two or something because I’m sure we’ll have a lot more questions for you next time.

JM: Yeah, well, it’s all in the books. You should have people… You know, the, My House Is Killing me, The Mold Survival Guide, it’s all full of a lot of this stuff. It’s amazing.

RS: We will put a link to that.

JM: It’s amazing.

RS: Yeah, we’ll link to that in our show notes.

JM: Yeah, it’s all the crazy stuff. It’s amazing.

TM: And Jeff, how would people find you if they wanna learn more or contact you? 

JM: Yeah, the website. Yeah, Yeah.

TM: Can you say that one more time? 


TM: Perfect. Okay. We can put a link to that too.

JM: Great.

RS: Excellent.

TM: Thank you so much, Jeff, for coming on the show.

JM: All right, thanks.

RS: Thank you. And we appreciate it.

JM: Enjoyed it. Take care.

RS: All right. And for the listeners, if you got any thoughts, questions, concerns, shoot us an email, our email is We’ll catch you next time.