Why Should I Test My Home for Radon?

I recently attended a conference to expand my knowledge of radon. What I learned was not only informative but also a bit alarming. As we mentioned in previous blogs, radon is a colorless, odorless gas that is the leading cause of lung cancer after smoking. Because there has been such an emphasis on the smoking aspect of lung cancer, radon’s contribution to this has often been overlooked. This is a shame because testing and mitigation systems can greatly reduce your chances of this major disease. Consider these statistics from the EPA’s website.

  • The risk of cancer from radon exposure at 4 picocuries per liter (a common level exceeded in IL) is similar to the risk of dying in a car crash!
  • If 1,000 people who never smoked were exposed to 4 pCi/L of radon, about 7 people could get lung cancer. Among smokers with this level of radon exposure, the number is 62 out of 1,000 people.

So how do you know if you have radon? The key word is “TEST”. Without testing, there is no other way that you will know what the levels are in your building. Again, radon is a colorless, odorless, tasteless gas. There are no known health effects, like headaches or coughing, to alert you of its presence. Proper testing is the only way to know what the pCi/L levels are in your home. The EPA action level for radon is 4.0 picocuries per liter (pCi/L), but the EPA suggests that mitigation should be performed if radon levels are from 2.0 to 4.0 pCi/L.

During my radon conference, a speaker made known his concern that his clients will typically have a single test when they purchase a property and then never test again. Radon testing provides a snapshot in time for a short period (usually 48 hours). Even if you had your home tested a number of years ago, it is an excellent idea to retest every five years. If you have a mitigation system installed, doing a retest every two years is recommended. Radon levels are typically highest during the winter, but it can be a good idea to test in varying seasons to get a good grasp of what levels are at various times of the year. Remodeling a home, installing new windows or replacing a roof can also affect your numbers.

Radon testing is not just about protecting your family’s health, it can also impact your property’s value. Keep in mind that if you are going to sell the property at any time in the future, chances are great that a buyer is going request a radon test. It doesn’t matter if your house is new or old, high end or low end, or even if it has a basement. Radon can be found anywhere in the country (as seen in the map below), and the only way to know for certain is to test. A letter showing that the property has been tested can put a buyer at ease.

Testing can save you and your family from the risk of lung cancer! If it will be tested anyway when you sell your home in the future, why not benefit now from a healthy home.

How Much Do Mold Inspections Cost?

This might be the most common question we receive. Unfortunately, there are no “one size fits all” type answers to this question. Think to yourself “How much does it cost to go to the dentist”? Well if you are just going in for a routine cleaning your cost could be less than $100, but if you need major work done it could be $1000’s. Much like seeing the dentist, each mold situation is so unique pricing can vary. Our mold assessments can cost up to $1000 (and occasionally higher for special projects), but the average cost for a typical residential project is about $600. Some major factors that influence the cost of an inspection are the size of the property, the distance from our office, the type and number of laboratory samples needed, and turnaround time needed.


We deal with mold problems in studio apartments up to large commercial office buildings and everything in between. Inspecting a mold issue on a bathroom window has different needs than a home that experienced a major flooding event. Assessing an attic in a large home in the suburbs with a complex roof design could take a few hours, where checking a wet ceiling from a plumbing leak can be done in a half hour.


We perform assessments throughout the Chicagoland area (and beyond), however, our office is located in Chicago. Depending on the location of your property, this can have a small effect on pricing. For special projects that we do throughout the US, travel may make up a major portion of the cost.


Laboratory samples are going to play the largest part in the total cost of a mold inspection. Some projects do not require any samples, or perhaps just one surface sample. Others may call for a number of air, surface, and dust samples. A healthcare facility may require viable sampling, whereas most properties are analyzed with spore trap samples. As a company, we always aim to maximize the amount of information gathered from sampling, while trying to keep pricing in check. Taking a sample in each room of the house might not provide additional information and can add hundreds of dollars to the cost, therefore, we try to only suggest sampling in areas and situations we think useful information can be gathered.


Hand in hand with laboratory samples is turnaround time. This is the time it takes to receive your report. In projects without samples, it is usually only a day or two before you receive your report. However, if samples are collected we must wait for those samples to be processed at the lab. A typical turnaround time from the lab is 3 business days.  When you add in time for drafting our report which interprets the lab results, our report follows a week from the inspection. In projects that are time sensitive, we can speed up the laboratory results as quickly as 24hr (and in some cases we can process the samples on site, giving you results in about an hour). Jumping to the front of the line at the lab does come at a cost, and weekend or holidays can compound the surcharge even higher.


You may see companies who advertise free or extremely discounted (~$100) mold inspections. If it sounds too good to be true, it’s because it is. Most of these companies are mold remediation contractors, and they use these cheap inspections as a way to get their foot in the door.  They typically suggest extensive remediation and potentially make thousands off of unneeded work. Companies who operate like this do so with an extreme conflict of interest. The party identifying the problem should not have a financial interest in its removal.


If you are having a mold or moisture problem of your own, and would like to talk with us about what we can do for you, please call our office at 312-920-9393

How Long Before I Get My Mold Report?

How Long Before I Get My Mold Report?

The answer to that question is – it depends.  

In the world of indoor air quality measurements, the turnaround time (TAT) for getting results can vary drastically.  While it is possible to give immediate feedback for some indoor air quality parameters, others can take a few days or even a few weeks depending on the type of sampling.  The timing is dependant on the type of sample that is taken and consequently the amount of time the laboratory needs to analyze the sample. In this blog post, I’ll cover the turnaround time for our most common mold work.

Mold Inspection TAT

For a typical mold inspection with a standard turnaround time here at Indoor Science, you will receive your written report in 5 business days from the day of the inspection.  

Here’s the breakdown:

  • It generally takes the lab 3 business days to analyze the samples.
  • Once we receive the laboratory results, we take 2 business days to write the report.  

Can you get it faster? Absolutely! For an added fee, we can speed up the report and samples as quickly as 24 hours. This is especially common during a real estate transaction. Just mention your interest in getting results faster and we can give you a quote.

Mold Clearance Testing TAT

Our company understands that after mold remediation is completed, you may need an inspection and lab results to be done quickly.  Indoor Science’s standard turnaround time is 3 business days if the project passes.  While that is the standard turnaround time, we have other options if you need the results quicker.  We can even get you results within an hour or less by offering on-site analysis.  

With on-site analysis, our microscopist can come out to the field and clear or fail a project on the spot!  We are one of the few companies that have a microscopist who is a Certified Spore Analyst through the Pan American Aerobiology Certification Board (PAACB) and trained at McCrone Research Institute.    

We offer a wide variety of testing besides the ones mentioned in this post – from asbestos to radon to laboratory-based tests for chemicals and allergens.  The turnaround time for these types of tests can range from a few hours to a few weeks!  More details about other turnaround times and different types of testing that we offer will be described in a future blog post.

We understand that timing can be critical when other factors are brought into the mix such as when you’re buying a home or when you have health concerns and need answers quickly.  Indoor Science can work with your schedule to determine what the best type of testing can be done in the time frame that you have.  If you want to know more about our services, call the office at 312.920.9393.

How Do You Test For Asbestos?


A common question we receive when clients are concerned about asbestos is “How do you test for asbestos?” In fact, there are many ways asbestos can be sampled. These methods include bulk, air, and dust sampling. In this blog post, I will go over these methods and how to decide which testing is best suited for your situation.

Bulk Sampling

Bulk sampling for asbestos refers to cutting out a small piece of the suspect material. This method is often employed when someone is concerned about a material, typically during a property transaction or renovation. The process of bulk sampling involves carefully collecting a piece of the material. It is imperative to disturb as little of the material as possible, as cutting it may cause asbestos fibers to become airborne. An asbestos inspector typically sprays the material with water amended with a surfactant such as dish soap prior to sampling to prevent fibers from getting into the air. The inspector will collect a sample using destructive methods to obtain a piece, typically around the size of a quarter. This may involve using a box cutter to cut out a piece of plaster or a coring device to cut into pipe insulation. The piece of suspect material is placed into a zip-locked bag and labeled for the laboratory.  The remaining surface can be patched, sealed, or covered to prevent future fiber release. Afterwards, the sample is sent to an accredited laboratory for testing.


In the laboratory, different types of microscopes evaluate if the material contains more than 1% asbestos. Materials containing more than 1% are considered “asbestos containing materials” and are typically regulated.  In a future blog, I’ll discuss the difference between the low cost, low sensitivity PLM (Polarized Light Microscopy) and the high cost, high sensitivity TEM (Transmission Electron Microscopy).

Air Sampling

A second method of testing asbestos is air sampling. Air testing is usually done when a potential asbestos-containing material has been disturbed or following asbestos removal to ensure that fibers weren’t released into the air during abatement. For example, air sampling would be suggested if walls were demolished in a home built before 1980 and the wall material was not sampled for asbestos. This may have lead to an accidental release of asbestos fibers. Another example would be after an asbestos material was abated, clearance air sampling would be necessary to ensure that fibers were not released during removal. The process is done by pumping air through a filter membrane about the size of a quarter to collect asbestos fibers.These tests typically run for up to 2 hours to achieve a total volume of up to 1,200 liters of air. Multiple air samples may be collected depending on the size of the project.

Dust Sampling

The final method we use to test for asbestos is dust sampling. This method is generally used to determine if there was a past release of asbestos fibers in an area. While asbestos can remain airborne for extended periods of time, it eventually settles into the dust. For example, if a past property owner did improper abatement work, there may be detectable levels of asbestos fibers in the dust even years later.

We are able to sample suspect dust by using a method called TEM microvac. This method involves using a TEM air cassette and vacuuming a 100 square centimeter area to evaluate the number of asbestos fibers present in the dust. Once collected and analyzed, we can use industry guidelines to observe if the number of asbestos fibers present are background, elevated, or highly elevated levels.


The wide variety of testing methods available allow for asbestos sampling in various scenarios. If you have a concern about asbestos, whether it be a material, air, or dust, Indoor Science has the capability to sample based on your concerns. We are licensed by the Illinois Department of Public Health, which is required to do asbestos inspections and testing. If you are interested in testing, feel free to reach out us at (312) 920-9393.

Top Causes of Indoor Moisture in Chicago


At Indoor Science, we compiled a list of the most prevalent indoor moisture problems for 100 homes in the Chicago area over the span of 6 months from August 2017 to January 2018. These were homes in which we performed mold or moisture inspections. In this blog post, I will discuss some of the most common moisture problems we encountered. These include water intrusion from external sources, damp foundations, plumbing leaks, insufficient management of moisture sources, and thermal bridging.

The most common cause of dampness is moisture intrusion from an external source. 54% of the homes in our analysis had this problem. These problems are typically caused by a roof leak or window leak during a heavy rain or ice damming. Leaks in roofs are commonly caused by damaged or missing shingles, weakness at penetration points, and failing flashing. Window leaks may be caused by failing caulk or sealant around the window frame.

The second most common moisture problem is wet foundations. For the 100 homes we analyzed, 23% had this problem. These are usually caused by a crack in the foundation.These cracks can form either from the soil subsidence around and beneath the home and in rarer cases improper curing of the concrete. However, these cracks are not necessarily caused by the home shifting. In fact, gutters and downspout are sometimes the culprits. When downspouts are clogged, causing water from the roof to pool around the foundation. Also if the soil around the home is sloping toward the foundation, water can pool around the exterior walls and exert pressure on the wall leading to moisture intrusion. Plants that are in close proximity to the foundation can also damage the foundation walls with its root system by exerting too much pressure on the wall. Lastly, the freeze/thaw cycle during winter can damage foundations. As water freezes after being absorbed into the foundation wall, it expands causing fissures to form.

20% of the homes in our analysis had moisture problems associated with plumbing leaks. Many problems arise from broken seals. Seals typically degrade with age and cause leaks in areas such as dishwashers, bathtubs, and toilets. Another common cause of leaks can be from temperature changes. When pipes are exposed to freezing temperatures this can cause water to freeze and expand, rupturing the pipe. The most common in my experience is the corrosion of pipes. Corrosion is the process by which a refined metal attempts to chemically stabilize itself into an oxide. This typically leads to rust formation inside the pipe causing degradation. The average lifespan of a pipe depending on the composition can range from 20-70+ years. As the degradation continues with age, the structural integrity of the pipe gets weaker.

The final common moisture issues often linked together are the improper management of indoor moisture sources and thermal bridging. Improper management of moisture sources often happens in bathrooms and kitchens. In bathrooms, the most common moisture source is humidity generated from showers. In an ideal situation, the humidity would be exhausted to the outdoors by an exhaust fan. However, sometimes the exhaust fans are not pulling an adequate amount of humidity out and may need to run longer than current usage. In some cases, there is no exhaust fan present which can send humidity throughout the home and may diffuse into a cold wall or above the bathroom into an attic. In the kitchen, the most common source of humidity is from cooking activities. As water reaches 212 degrees Fahrenheit, it begins to boil. Combustion of gas burners also gives off humidity.  This humidity is often managed by turning on the stove hood to exhaust the moisture out. However, many exhausts do not exhaust outdoors and are in fact recirculating the air. And in other cases, some homeowners do not operate the exhaust.

This leads us to moisture issues associated with thermal bridging. Thermal bridging refers to an object or area that is more thermally conductive than the surrounding areas. Many objects in the winter can become thermal bridges such as exterior walls, HVAC ducts/vents, windows, etc. When moisture is improperly vented in the home, it can condense on cold surfaces caused by thermal bridging. For example, if a bathroom improperly vents moisture, it may condense on walls where there are studs due to thermal bridging.

While these are some of the most common sources of moisture that we investigate, there is a myriad of others that we also come across. These moisture issues can often lead to the formation of mold growth. If you suspect that your home has one of these moisture issues and are concerned with mold, please reach out to us to assess your property.


Is Mold In An Attic A Big Deal?

The answer is that it all depends.  Let me try to explain.  Mold needs moisture in order to grow.  No moisture; no mold.  In an attic space, moisture can occur from a leak in the roof or from condensation due to elevated levels of humidity (typically from improper ducting from a bathroom exhaust fan).  Mold has the possibility of growing on attic sheathing, which is typically a wood product (something mold likes to eat).  A surface sample can help determine if these stains are mold growth.  

Many times, even if a surface sample does show mold growth, it may not be an indication that it is resulting in excessive levels of mold spores in the living spaces below.  Why is that?  It’s something called “stack effect”.  This means that warm air is more buoyant and rises. Air generally moves from the lower levels of a house up through the top.  If mold growth originates in the attic, it is hard for spores to fight against this pressurization.  Attics can also (although not always) have a higher level of ventilation which can help remove the spores.    

Does that mean that it’s not a big deal to find mold in an attic?  Healthwise, issues can still occur if an occupant has a hypersensitivity to mold and there is an HVAC system or ductwork in the attic space.  Mold spores can be sucked up into the return ductwork and spread throughout the home.  Even if the spores are more or less contained in the attic, the very presence of mold indicates a moisture issue which can lead to rot and destroy sections of the roof.  Although not a huge health issue, removing rotting wood can be a very expensive project.

We have seen attic mold discovered during a real estate transaction kill the deal.  Therefore we recommend people remediate mold in their attic if for no other reason than to avoid concerns from a nervous purchaser in the future.

So to answer the question about how big a deal it is to have mold in the attic, one needs to contemplate how moisture is entering into this space and how much damage is occurring because of it.  Occupants also need to ascertain if there is any possible way that mold spores can access the living areas of the house from the attic.  Although mold in an attic is typically not a huge health issue, it does represent possible dangers and excessive costs if not dealt with immediately.    

If you would like to perform a mold inspection in your Chicagoland attic, give us a call at 312.920.9393.  For additional information, check out our website at Indoor Science  – Mold Testing

If I use “low VOC” or “No VOC” paints can I still have air quality issues?

We receive this question a lot from clients who may have air quality concerns after a renovation project. Many times people think they are doing the best thing by purchasing products with a label that states “Low VOCs” or “No VOCs”. After painting, they may notice a strong odor or even experience respiratory-related health issues. Understandably these people may be very frustrated because they thought they were taking an extra step, and also paying quite the premium, to avoid the chemical emissions from the paint. The truth is, many of those labels are extremely misleading.


Industry VOC regulations are different around the country, so in this post, I won’t be getting into specific requirements for different areas. The commonly referenced number for “low VOC” paint is less than 50 g/L, and for “no VOC” paint less than 5 g/L. A major issue with some of these products is how the term VOC is defined and chemicals that are exempt from being listed as a VOC.  The EPA exempts a number of VOCs that are not photoreactive (smog-forming). While this is important for outdoor air quality, these exempted VOCs can still cause indoor air quality problems.


Another hidden issue with these products comes into play when they are tinted or other additives are added to the mix. These products are not taken into consideration when a paint is advertised as “low” or “no” VOC, usually only the base paint meets those requirements.


Ventilation is key to avoiding IAQ issues with any type of painting. It is always best to have as much ventilation as possible while you are painting, and also afterward to allow for the VOCs to off-gas as much as possible.

Can You Inspect My Attic for Mold?

We receive many calls from property owners who are concerned about mold in their attic.  Most attics tend to be unfinished with exposed sheathing, wood supports, and insulation.  Because of this unwelcoming environment, property owners rarely go into their attics which can leave undetected mold problems for long periods of time.  In October of 2017, one of our project managers, Scott, posted about mold problems that went unnoticed in his attic.

When property owners want mold testing inside their attic, they usually ask – How is a mold inspection done in an attic?

In a typical mold assessment in the living spaces of the home, we look for signs of current moisture using an infrared camera and moisture meter.  These two devices are excellent for identifying dampness that may not be visible to the naked eye.  We scan floors, walls, and ceilings to find where any hidden dampness may be.  We also do a thorough visual inspection for mold and often include surface and or air samples. In attics, we can do a visual inspection too, but at times we can be hindered by access.  We look for visible mold and check if any exhaust fans are dumping humid air into the space. In an attic, we also use the infrared camera and moisture meter to find current moisture in the same way as in the living spaces. We also collect surface samples of questionable and discolored surfaces in the attic the same way we might do so inside a home.  However, air sampling in an attic is controversial.

Attics are different indoor environments from the living spaces due to their unique ventilation.  In our climate, most attics are ventilated, which means outdoor air is continuously passing through the space.  Because the ventilation is different from the other living spaces in the home, it is not recommended taking air samples in attics. Attic air is more reflective of outdoor air.   

A few of the takeaways are that we identify areas containing mold and determine the possible causes of any moisture problems.  I should also mention, that attics are considered confined spaces and can be dangerous for an adult person to inspect.  There are times when we are limited in the degree to which we can inspect attics due to accessibility. (We don’t want to fall through your ceiling, as much as you don’t want us falling through your ceiling!).

When setting up an appointment up with us, it is important to discuss your interest in inspecting your attic and to describe accessibility issues. We want to come prepared! To read more about our mold testing procedure, follow this link

Featured Asbestos – Crocidolite



When most people imagine what asbestos looks like, they often think of a white fibrous mass. However, asbestos varieties come in different shades such as brown and blue. The blue asbestos is called Crocidolite.

For my fellow geology enthusiasts, Crocidolite is actually the name of the fibrous form of the blue mineral known as Riebeckite. The high sodium content in the mineral gives it the iconic blue color. Crocidolite and Riebeckite both belong to the amphibole asbestos group which also is the group of 5 of the 6 regulated asbestos minerals.

Amphibole asbestos minerals such as Crocidolite were often used in thermal system insulation in conjunction with Chrysotile due to their higher temperature resistance and durability. Crocidolite, as with other amphiboles, are considered to be more harmful than Chrysotile due to their needle-like shape and higher durability and more linked to mesothelioma.

While Crocidolite is mostly used in thermal system insulation such as magnesium block, it was also previously used in cigarette filters. In the 1950s the Lorillard Tobacco Company produced Kent cigarettes with their new “micronite” filter. This filter was marketed as being safer than other cigarettes because it filtered out toxins and particles. This marketing was successful at time due to rising awareness of the relationship between smoking and lung cancer. The cigarette company even used letters from physicians promoting the safeness of the filter.  Many workers at the factory who produced the filters succumbed to mesothelioma.

Remember that asbestos isn’t always white and the only way to detect its presence is with a laboratory test.


What is the difference between carbon monoxide and a gas leak?

With the freezing temperatures outside, we can be assured that winter has finally arrived in Chicago.  Now that furnaces are running, we are often asked to investigate the possibility of elevated carbon monoxide and/or a gas leak in a client’s home.  Many clients have a tendency to confuse these two health hazards.  Let’s review the origin of each hazard and how to avoid elevated levels in the home.   

Carbon monoxide is a product of combustion, or to be more precise, improper combustion.  The health hazards associated with this is asphyxiation and possible death.  This improper combustion can occur from furnaces, gas or wood fireplaces, water heaters, and poorly maintained gas stoves and ovens.  On one assignment, I discovered that the elevated level of CO was due to the owner warming up her car in the attached garage.  It would be better to pull out of the garage before letting your car warm up.  Because this carbon monoxide is colorless and odorless, we advise having a carbon monoxide detector operating in the home to alert you if there is a danger.  We also advise:

  • keeping gas appliances clean and well maintained
  • ensuring combustion venting is intact and exhausting to the outdoors
  • avoiding excessive negative pressure, which can prevent combustion gases from exhausting

A gas leak is pretty straightforward; it’s a leak of natural gas from a pipe serving a combustion appliance (furnace, water heater, etc.).  The primary constituent of natural gas is methane, which is an odorless, colorless gas that is difficult to detect through our five senses.  That is why a tracer gas is added (known as mercaptan) to help detect the location of the leak.  Although it’s possible that people can develop health symptoms (headaches, etc…) from a leak, the greatest danger is from a possible fire or explosion.  The best form of prevention is to sniff around the gas lines of your house and see if you smell anything out of the ordinary.  Some of our clients have thought that they were smelling mold or sewer gas when in reality they were smelling the mercaptan gas.  Mold has a more musty odor, whereas mercaptan has more of a sulfur or rotten egg smell.  If you suspect anything, give your local gas company a call and ask for someone to come out and inspect the property.  Typically the gas company does not charge to come out and inspect the possible leak.

Both of these issues have harmful, if not lethal, effects on one’s health.  It is to your advantage to take the proper precautions and ensure healthy air. 

Mold Certifications

The mold industry can seem like the wild west. In most states, including Illinois, there are no requirements for someone to call themselves a mold inspector. You may find someone who advertises themselves as being “certified” and features all kinds of official looking seals and stamps on their website, but how do you know if that certification is even worth the paper it is printed on.

There are countless mold certification programs available. At Indoor Science our project managers carry certifications from the American Council for Accredited Certification (ACAC). ACAC certifications are independently accredited by the Council of Engineering & Scientific Specialty Boards. This third-party verifies that certification programs are developed and operate according to their requirements. Many “certifications” are as simple as: you send a company a check, take a short webinar, and they send you a certification. ACAC certifications require that applicants submit verifiable education and project history, and applicants must pass an exam which is proctored by a third-party. These are all steps which the ACAC takes to assure that their certifications are set above many of the others that are available.

In some states which require a license, the ACAC is the ONLY recognized certification program. ACAC exams are used for Florida, New Hampshire and Maryland state regulatory programs.

So although Illinois doesn’t require ACAC certification, it is good practice to hire a company with ACAC-certified project managers.

In a future blog post, the owner Ian Cull, PE, CIH will describe the highest certification recognized in our field: the CIH (Certified Industrial Hygienist).  

House Dust: Think Dust Mites!

A few weeks ago, I blogged about some of the components of house dust.  This week, as promised, I will discuss the presence of house dust’s most famous contaminant: dust mites.  

Dust mites are microscopic arachnids, which means they are in the same family as spiders.  They do not bite like bed bugs, but they can trigger an allergic reaction.

In a 1 gram sample of house dust, it is not uncommon to find thousands of dust mites (Portnoy 2013). That’s a lot of dust mites!  These creatures are about 245 microns wide and 440 microns long, so about the size of a grain of sand.  They feed on dead human skin cells in the dust.  This is a plentiful food source since a human sheds about a million skin cells per day (Colloff 2009).  Environmentally, dust mites respond well to humidity, in fact, they thrive when the relative humidity is higher.

The allergen for dust mites actually comes from dust mite feces.  Since 27.5% of the population in the United States is allergic to dust mites, it may be helpful to know that while humidity levels might be below 60% in the middle of a room, they can be much higher under the covers (Arbes 2005).  To get some relief from the allergic effects of these critters, it is recommended to monitor humidity levels in the home and maintain them below 50% (Cunningham 1996).  Using encasements around pillows, mattresses, and box springs can reduce the number of allergens that can escape from these materials.  Also, washing bedding, curtains, and other fabrics regularly in hot water can help eliminate the microscopic arachnid.

If you are concerned about dust mites, IAQ consulting companies like ours offer a test that checks for dust mite allergen.  However, in many situations, cleaning and reducing humidity levels can provide some relief against the little pest.  

The next time you wake up in the morning and start rubbing your eyes think dust mite feces!


Arbes, S.J.; Gergen, P.I.; Elliot, L; Zeldin, D. Prevalences of Positive Skin Test Responses to 10 Common Allergens in the U.S. population: Results from the Third Nutrition Examination Survey. I Allergy Clin Imunol. 2005, 116, 377-383.

Colloff, M. Dust Mites, 1st Ed.; Springer Publishing: New York, 2009.  

Cunningham, M.I. Controlling Dust Mites Psychrometrically – A Review for Building Scientist and Engineers. Indoor Air. 1996, 6, 249-258.

Portnoy, J., Miller, J. D., Williams, P. B., Chew, G. L., Miller, J. D., Zaitoun, F., … Wallace, D. (2013). Environmental assessment and exposure control of dust mites: a practice parameter. Annals of Allergy, Asthma & Immunology : Official Publication of the American College of Allergy, Asthma, & Immunology, 111(6), 465–507.

I’m Dreaming of a White…. Asbestos?



As we have discussed in previous blog posts, asbestos is a versatile substance. Although it is typically only thought of being used in building materials, its usage eventually branched out to Hollywood. Due to the texture and pale color of chrysotile, a common form of asbestos, it was sometimes used as a snow substitute in films.

In the critically acclaimed film the Wizard of Oz, chrysotile asbestos was used during the poppy field scene when Dorothy and her companions are fleeing from the Wicked Witch of the East. There, they have a spell placed on them, causing the group to become incapacitated. They later awaken in the field covered in snow. Behind the scenes, the “snow” used was actually industrial grade chrysotile asbestos. Even the scarecrow’s costume and the wicked witch’s broom were made of asbestos to protect the actors during scenes involving flames.

In the film White Christmas, actor and singer Bing Crosby sings the title song of the film while snow falls on him. In reality, a stagehand was dumping chrysotile asbestos down to simulate snow. While the film “It’s a Wonderful Life” is widely claimed to have used asbestos in their “snow”, it was actually a substance called foamite commonly used in fire extinguishers. However, it is reported that asbestos may have been used on the set.  

Even outside of film studios, asbestos “snow” was commercially available for Christmas decorations. Previously cotton was used on ornaments and Christmas trees, however asbestos was marketed as “safer” due to cotton-based snows being a fire hazard. The decline of asbestos snow came around during the time of World War II when asbestos was needed by the Navy for ship building.

If you don’t believe me, as I was researching information for this blog post, I discovered that the asbestos snow is still available on E-Bay!

References (2017). Asbestos in Fake Snow -. [online] Available at: [Accessed 21 Dec. 2017]. (2017). OSH in the Movies: The full list | | Blogs | CDC. [online] Available at: [Accessed 21 Dec. 2017].

IMDb. (2017). The Wizard of Oz (1939). [online] Available at: [Accessed 21 Dec. 2017].

What’s in House Dust?

House dust can contain many different particles and contaminants.  The type of dust and the composition can vary depending on climate, region, the number of occupants, and the activities performed in the space.  Researchers estimate that one-third of dust originates from indoor sources such as fabric fibers, human skin cells, animal fur, decomposing insects, food debris, and lint.  Approximately, two-thirds come from soil and particles from the outdoors.  I also found out that household dust may also contain several dangerous chemical contaminants.

In one study, researchers found multiple types of plasticizers and flame retardants in 90-100% of the dust samples taken.  Plasticizers are used to soften plastics in vinyl flooring, food containers, and cosmetics.  Phthalates are common chemical compounds that makeup plasticizers.  Different types of phthalates were found in the dust samples.  This result is concerning because phthalates are known as endocrine disruptors.  The human endocrine system regulates hormone levels inside the body.  The endocrine disruptors negatively affect the body by causing developmental problems, cancer, and birth defects among other issues.  

Research is still being conducted on the chemicals that can be found inside of dust but I think the evidence so far shows how common house dust can be a real problem in terms of indoor air quality.  In a future blog post, I’ll cover the most notorious contaminant in dust… dust mites.


Layton, D. W., & Beamer, P. I. (2009). Migration of Contaminated Soil and Airborne Particulates to Indoor Dust. Environmental Science & Technology, 43(21), 8199–8205.

Consumer Product Chemicals in Indoor Dust: A Quantitative Meta-analysis of U.S. Studies  Susanna D. Mitro, Robin E. Dodson, Veena Singla, Gary Adamkiewicz, Angelo F. Elmi, Monica K. Tilly, and Ami R. Zota Environmental Science & Technology 2016 50 (19), 10661-10672 DOI: 10.1021/acs.est.6b02023

Foreclosures And Hidden Mold

A funny thing happened during a recent inspection.  The client had purchased a home roughly four years ago.  She was concerned when a visiting relative complained of having symptoms of her mold allergy while in the property.  The client called a mold company to come in and do air testing.  Picture her shock when she discovered highly elevated levels mold in her basement.  She called our company to get a second opinion and I was on the case.  

And what a complex case it was.  Our air samples confirmed that there were elevated levels of Chaetomium in the air, but there were no visible signs of mold growth.  I cut holes in the basement walls, but couldn’t find mold growth on any drywall.  This didn’t make any sense.  Typically, when you see these levels, there is a moisture source and there should be some kind of evidence of mold growth somewhere in the basement.  

Finally, in exasperation, I asked if they purchased the home as a foreclosure.  When the answer turned out to be “yes”, our investigation dug deeper.  After further investigation (and more wall cutting) we discovered what had happened.  The property appeared to have had a past flooding event from an upstairs bathroom.  This water continued down into the basement and mold growth developed on the drywall, wood framing, and ceiling.  

What happens so many times in a foreclosure is that contractors start to cut corners.  Sure, they removed the drywall that contained some of the mold, but they never bothered to remove the physical mold on the basement ceiling joists and wall studs.  They just covered it up with new drywall.  What could go wrong?  

Mold growth on wood studs

Mold growth on ceiling joists

What did go wrong was that the inside of the walls and ceiling had hidden mold growth.  Because the basement drywall was dry at the time of the inspection, it made it next to impossible to locate the growth.  The current owners walked in and saw a great house at a great price in a great location.  What they bought was a basement with hidden mold.  

In addition to the above example, there can be other sources for moisture to get into a distressed property.  During a foreclosure, the home can be unoccupied for several months.  When these properties are occupied during a humid summer, there is air conditioning that removes moisture out of the home.  But during many foreclosures, the electricity is shut off; this stops this dehumidification of the air and cuts power to the sump system.  The end result can be moisture in the home and then mold growth.

If you see a little mold in a distressed property, chances are there is a great deal more hidden somewhere else.  Try to detect any moldy odors by the walls.  Pull up the corner of carpeting and see if there are any dark stains on the carpet tack strips.  Be very cautious if you see any water lines on unpainted walls behind furnaces or water heaters.   

An interesting point regarding air sampling.  In this project there was no indication of a problem because there was no visible mold, no water stains, no mold odors.  The only thing that alerted us to problem that prompted us to dig deeper was air sampling.  Although in some circles air sampling via spore traps gets dismissed, there are many projects where it proves to be very useful.

And above all, hire a professional mold inspection company to inspect a distressed property.  When you are worried about hidden mold, be sure to include air sampling.  Our clients were happy to finally find the source of the mold, but it did come at a cost.  Foreclosures can be tricky, but it pays to take the proper precautions and save yourself the headaches later on.

Questions From The Field


mold under the microscope

During one of my recent inspections, a client presented me a list of questions after the assessment. I often encounter these questions in the field, so I picked out some of the best questions and I am providing the answers below.

Q1. Is everything in a room where mold spores are present assumed to have mold spores?

A1. Mold spores are everywhere and under normal conditions are generated in the outdoor air. They typically settle over time and are a common component of house dust. If there is an elevated spore count in a room, there will likely be additional spores settling on the contents in the affected room, joining the normal, background spores already on the surface.

Q2.How do I decide which items can be kept vs what can be cleaned vs what must be thrown away?

A2. If the items do not sustain mold growth, it can be cleaned and/or HEPA vacuumed to remove settled spores. If the item is sustaining mold growth and is a porous material, it should be discarded. If the item is sustaining mold growth and is non-porous, the item can be wiped clean.  If the item is wood and is sustaining mold growth, we generally recommend roughing the surface using a wire brush or sandpaper to remove the mold.

Q3. When do I clean my air ducts?

A3. Currently, the EPA does not recommend routine cleaning under most circumstances. The reason is that there is not enough concrete evidence showing that duct cleaning may improve air quality. However, duct cleaning should be performed if visible mold is seen in the ducts or other HVAC components.

Q4. Under what conditions do mold spores grow and multiply?

A4. Think of spores as being like seeds of a plant. Spores grow when there is adequate moisture and a nutrient source. Adequate moisture can come from flood water, exterior moisture intrusion, condensation and elevated humidity. Nutrient sources from mold are commonly dust, drywall’s paper facing, and wood.

Q5. What is the relative value of ERMI tests when compared with air tests?

A5. ERMI tests give insight into historical mold activity, whereas air samples tell current conditions. Because of this difference, ERMI tests and air samples running concurrently may yield vastly different results. Please note that the EPA currently recommends the ERMI tests for research purposes only.  We can still perform ERMI testing, but we do it in conjunction with a more traditional mold inspection.

Mold Testing In Winter

Winter brings a unique situation for environmental consultants. With the colder weather and snow cover on the ground that comes with winter in Chicago, there are usually very low outdoor mold levels. Occasionally we can even see outdoor air samples that have no spores present. If you recall from my last blog post on interpreting mold results, environmental professionals use outdoor air samples as a primary guide for determining if there is evidence of indoor mold growth. In areas where there are consistent sub-freezing outdoor temperatures or where snow cover persists for the entirety of winter, some inspectors will choose not to collect an outdoor sample. Here in Chicago, our winters can be dynamic. We can go from 40 degrees and no snow cover to sub-zero and 5” of snow on the ground in the blink of the eye. Even periods of a brief thaw can cause outdoor fungal levels to spike, and therefore affect the natural levels of mold in the indoor air. Because of this, we always collect an outdoor reference sample. So, how do they know if something is elevated when the outdoor control sample is very, very low?


Without the scope of an outdoor air sample, we have to be extra careful with interpreting the indoor results. We use indoor control samples in unaffected areas as one guide. This helps establish what “normal” levels would be expected in the building. Moderate levels of common outdoor types such as Aspergillus/Penicillium and Cladosporium indoors, which in the warmer months may be similar to the outdoor levels, in winter can be signs of possible indoor mold growth when an outdoor source can be ruled out. Also, any amount of water damage indicating mold found indoors, such as Chaetomium, Stachybotrys, or Fusarium to name a few, found in the indoor samples raise concern.


Interpreting air samples can be one of the largest challenges for an environmental professional. There are no concrete guidelines available and the results are unique to each job. Having someone who is well trained and experienced reviewing your results is one of the most important factors in identifying mold concerns indoors.

It Can Happen to Me – AGAIN!!!

Just as I thought that I would have my hands full with the issues in my attic, I was forced to contend with another issue – radon!

As I have mentioned in previous blog posts, we want the radon levels in our home to be under 4.0 pCi/L.  I have tested the levels in my unfinished basement and discovered that my levels were at 5.0 pCi/L.  I tested this a few more times to make certain that there was no mistake, but to no avail.  I need to have a mitigation system installed in my home.  

And so off I go in search of a mitigation company.  Some companies come to the property to provide a more accurate quote.  Others provide a quote over the phone after answering a series of questions.  And some don’t bother returning your phone calls.

What should one look for when looking for a mitigation expert?  First and foremost, you should confirm that the person doing the work is licensed as a radon mitigation professional.  Illinois requires a state license, but most other states do not have a licensure program.  In addition to actually returning your calls, we recommend hiring a company that is bonded and insured.  They should also have an excellent reputation for the quality of their work. This can be verified on several websites such as Angie’s List and Yelp.

Other things you may want to consider is if the company will send you a written estimate and if they offer any warranties.  Is the warranty written in clear, unambiguous language?  Will they warranty the effectiveness of the system unconditionally?  Are parts covered?  For how long?  The pricing may vary, but just because they are cheap doesn’t mean that they will ensure the quality of their work.  You may also want to see if the warranty will include new owners to the property.  

Case in point, I have heard of one company that reportedly told his client that he couldn’t guarantee that the levels of radon will be under 4.0 pCi/L after the system is installed.  I am here to tell you that if I am paying this company any kind of money, the very least I will expect is that it will be under the EPA and IEMA recommended level of 4.0 pCi/L!  And it will also be covered under some kind of warranty for parts and labor.   

As for now, I think I have selected the right company.  They are licensed, bonded and insured.  They have an excellent reputation and they warranty their work.  They actually came out to the property for a physical inspection – and they were the cheapest!  As I have discovered, when it comes to your family’s safety, it is important to do the necessary research.  

Fundamentals of Mold Remediation

My new book, “Fundamentals of Mold Remediation“, was published this week.  Over the past few years, I have been collecting my thoughts from designing and evaluating countless mold remediation projects.  I have seen some mold projects done right, and many more projects done wrong.

There are a number of guidelines and standards on mold remediation, so why did I find it necessary to publish a book on the topic?  The available guidelines don’t always agree with each other, and they often deviate from the common practices done in the field.  Also, the formality of standards and guidelines often make them difficult to read.  My target was a 100-page book that was easy to read and reference.  Although the book was written with mold professionals in mind, a homeowner, building engineer, or maintenance staff can readily understand and apply the concepts.


The book is now retailing for $65 on Amazon, but if you are a client of Indoor Science, you’ll be able to pick up a free copy at our office starting November 15, 2017.  More than selling books, my goal for this project was to help individuals who are serious about doing mold remediation right.  In some small way, I hope I can help the profession become more standardized and elevate the quality of work.

Patio Doors That Make You Weep

Several of our clients have experienced water intrusion around sliding glass doors.  There is a mixed bag of flashing problems that can cause water intrusion.  Flashing materials, weep holes, and weep ropes are used to drain water that gets behind the masonry.  

In this image, the black material beneath the vertical bricks is the flashing that drains the water out and away from the building.  The weep rope is supposed to help draw water out from behind the masonry to the outside.  This main issue with this picture is that the weep hole looks small and the rope looks pinched.  


Here we can see that a translucent sealant was placed right on top of the flashing.  This sealant prevents the water from moving to the outside and traps it behind the masonry.  The sealant was only present towards this end of the patio door and not the other.  Inside, a lot of moisture was found directly behind this section of the door and not on the other side where the sealant was absent.

At this property some flashing was present but it did not extend far away enough from the masonry.  The flashing should come out and overlap.  In this image, rust is visible between the door frame and the concrete.  This is a good indication that moisture is actively getting into this patio door.


Here, it appears that new mortar was placed to seal up the weep hole.  It may have been confused for just a simple opening. They probably sealed it up trying to prevent water from coming in, not realizing they were preventing water from coming out! Weep holes don’t always contain weep ropes.  A mesh screen can be placed over the weep hole to prevent insects and debris from entering the cavity. No matter what type, they should not be sealed shut.


In all of the properties shown above, there was moisture detected behind the patio doors.  To prevent mold growth you need to address the underlying moisture issue that is causing the dampness.  If there’s moisture surrounding a glass sliding door, it would be wise to check out the exterior of the patio door to determine if there are any anomalies that could cause water intrusion.