Is October “Mold Season” in Chicago?

“This is the time of year for mold around Chicago.” This isn’t a quote from an allergist, but rather Dusty Baker, the manager of the Washington Nationals (and past Cubs manager).  He made this statement at a press conference after game 4 of the NLDS baseball playoffs, which was postponed due to rain. This was in response to ace pitcher Stephen Strasburg feeling under the weather and declining to start game 4. This blog will examine Dusty Baker’s observation and let you know… is October mold season in Chicago?

There are many factors that influence the outdoor mold levels at any given time. The time of year, precipitation, wind speed and direction can all be factors. Seasonally, winter has the lowest levels of outdoor mold. With snow cover, we can even see outdoor levels at or very close to zero. In my experience, the highest levels that I see in the lab are during a wet spring period, and late summer. At these times we can see total outdoor counts over 10,000 spores per cubic meter of air.


Usually, by October, I start to see outdoor mold levels start to fall off towards their winter lows. This fall Chicago has been unseasonably warm, and over the past week, we have had rain off-and-on. Rain can cause higher levels of many common outdoor mold types such as basidiospores. The American Academy of Allergy, Asthma & Immunology’s National Allergy Bureau Pollen and Mold Report reported a “High” designation for the Chicago area on October 10, 2017. All of these factors are telling me that while it isn’t the common time for high mold levels in Chicago, we are seeing unseasonably high levels currently.

At the end of the day the mold didn’t seem to bother Stephen Strasburg and the Nationals too much, as they shutout the Cubs 5-0.

It Can Happen To Me

I have been living in my home for a number of years now and really don’t have any reason to go up in my attic.  I would need to get a ladder out and set it up in the middle of my hallway and access the attic through a small door in the ceiling.  But one day I came to the conclusion after doing my job for a number of years that it was time that I perform a visual inspection to see what’s going on.  I dragged my feet for years.  Now was the time.

And what I found shocked me.

I discovered dark stains on the north side sheathing of my attic (See Photo #1).  These stains surrounded several roofing nails on this side.  This is especially concerning because my bathroom exhaust is located in this area and I noticed that the bathroom duct was not properly connected to the outdoors (See Photo #2).  It is highly likely that humid air from the bathroom is hitting this attic wall to create condensation.  With this condensation, we have the distinct possibility that the dark stains are mold growth.

Photo #1 – Stains on attic sheathing

Photo #2 – Improperly connected duct


I am sure that I will be writing about how we will respond to this in the future.  However, if this new discovery will teach me anything, it will be a new found sense of greater empathy for those who encounter this exact same problem.  So please take my advice as we start to go into this winter season.  Poke your head into your attic space and examine your attic walls to see if there are any stains or water damage.  Check to see if your bathroom exhaust is properly connected to the outdoors.  If your attic has a wood floor, examine if there are dark spots on the flooring that might indicate water dripping from the roofing nails.  And most importantly, don’t do what I did and put it off.  Regularly checking your attic (even if there were no problems in the past) will save you a load of headaches later.  Trust me, it can happen to me.

ERMI Testing Vs. Air Samples

Very often we receive calls from very concerned people that need help determining if they need an Environmental Relative Moldiness Index (ERMI) test or not.  The range of knowledge in the general public for this type of test varies.  In this post, I will highlight a few points to keep in mind when deciding on doing an ERMI test.First, let me provide some information per the Environmental Protection Agency’s (EPA) website on ERMI testing.  ERMI stands for Environmental Relative Moldiness Index.  The analysis from this test can be used by researchers to estimate the levels and types of mold inside a property.  The test is done by collecting a dust sample.  Since mold spores can settle onto dust, the DNA from the mold in the dust can be identified, thereby providing information on what types of mold are present.  However (and this is highlighted in bold lettering on the EPA website), “the ERMI should be used only for research.  The ERMI has not been validated for routine public use in homes, schools, or other buildings.”  The EPA also recommends that water damage is assessed during the inspection since moisture issues are what cause most mold problems.  

Our company performs several types of mold tests including ERMI and air samples.   Air samples differ from ERMI because no settled dust is used.  Instead, air is drawn through a cassette and any spores present are deposited onto a glass slide in the cassette and ultimately viewed through a microscope.  The laboratory analysis can tell us the concentration of mold that was found in the air along with the types of mold (generally, down to the genus level).  

So the main difference is that ERMI collects spores and DNA from dust, whereas air samples collect spores from the air.  What’s the big difference?  The spores settled in the dust provide more historical information and air samples provide more current information.  Is one better?  Not really, they are just different.  Analysis between the two types is another main difference with ERMI detecting DNA via polymerase chain reaction and most air samples being analyzed via the microscope.

ERMI tests use a statistical formula to provide a single ERMI number.  Interpreting that ERMI number can be a big challenge.

When potential clients ask us to perform an ERMI test, we first recommend that we do a visual inspection and moisture evaluation.  We recommend that they also do more traditional spore trap testing alongside ERMI.  This way we can provide them with both historical and current information regarding the mold levels in their home.   

This blog article is just scratching the surface about ERMI.  Please leave a comment if you have any questions.

EPA Website:

Featured Asbestos – Chrysotile



Did you know that there are different types of asbestos?  There are six different minerals that we collectively call “asbestos”.  

Chrysotile is the most commonly found mineral in asbestos-containing materials. According to OSHA, Chrysotile makes up 95% of the asbestos found in asbestos-containing materials in the United States.

Chrysotile fibers are typically more curly while other (amphibole) asbestos fibers are more needle-like. While the fibers can still cause serious health effects such as lung cancer and mesothelioma, it is generally considered less toxic than amphiboles. This is due to the fact that the needle-like amphiboles are able to go deeper into the lung tissue and more durable than Chrysotile.

For my fellow geology enthusiasts, here are some facts about its origin. Chrysotile is a white asbestiform mineral and the only asbestos mineral that is from the serpentine group, while the other five are from the amphibole group. Chrysotile typically appears white in color and has a curly fibrous crystal habit.  Chrysotile forms when metamorphic serpentinite is hydrothermally altered, which causes Chrysotile to form in veins of the source rock. The source of most of the Chrysotile used in American products originates from Canadian mines. Serpentine is the state rock of California. Because of its relation to Chrysotile, there have been numerous attempts to remove it from its status.

In my undergrad years, I remember during a mineralogy lecture my professor bringing out several minerals to the lab table. My fellow colleagues and I walked over to see this strange looking fibrous bundle. One of the students in the class enthusiastically picked up the mineral, before our professor rushed over quickly to inform us it was asbestos. Little did I know at the moment, I would encounter this mineral many more times in the future.

More on the Interpretation of Mold Air Samples

Are you staring at the results of a mold test and struggling to figure out what it all means?  Let me try to help you.


The most common method used for mold air testing is uses a spore trap cassette. Because there is always a background amount of airborne mold spores, a key step in collecting air samples is to have a “reference” sample collected from the outdoor air at the time of the indoor testing. Since there are no guidelines on acceptable mold levels in the air, an outdoor sample is the best tool for interpreting the results of the indoor samples. Without the outdoor sample, you are limited in what you can gather from the results of the indoor samples.


There are various D.I.Y. air tests you can pick up at your local hardware store requiring you to place out a petri dish for several hours. Most of those tests are not very helpful in giving you any sort of usable data to evaluate the air in your home and as a general suggestion should be avoided.


Interpreting mold levels can be tricky. If you would like feedback on your mold air sampling results, please comment below and I will do my best to give any feedback I can in my free time. The views expressed in the blog post and comments are my own, and not necessarily those of Indoor Science. If you need a more immediate response regarding your results you can book a 30-minute phone consultation for $98 by clicking here.

Common Errors to Watch For in Mold Remediation

The drill goes something like this.  A mold expert is called into to your home and you find out the bad news that you have mold in your home.  The remediation company is called in and after a few hours or a few days worth of work, they report that you are clear of the mold.  What a relief!  That is until your mold expert is called back in to reinspect the work.  It’s been my experience that the remediation company can leave three major items incomplete during the remediation.  

  1.  Killing, not removing, mold

I have had some clients inform me that “The only good mold is dead mold.”  I usually correct them and say “No, the only good mold is physically removed mold.”  Whether it’s on drywall, wood, or dust, the only way to be sure that mold is not going to pose a danger is to safely remove it.  Some companies might see mold growth on attic sheathing and spray anti-microbial fungicide to kill it.  We call these companies “Spray and Pray” because the fungicide can often times look like white primer paint and it is difficult to determine if the mold is properly removed.  Then they pray the mold doesn’t come back!  Remember, even dead mold can be allergenic and toxigenic.  Be sure to physically remove that mold!

  1. Not scrubbing the air

The second issue that can ruin a remediation job occurs when the air is not properly cleaned of mold spores.  When workers are tearing down walls or scraping the mold away, we find that a large number of spores have been released into the air.  The air after remediation can have a higher level of airborne spores than before the work began.  This is why containment is so important; the plastic walls prevent large numbers of spores from going throughout the rest of the building.  Another issue is not running the air scrubbers or negative air machines for a long enough period of time to properly clean the air.  Air scrubbers can suck the spores through a HEPA filter, but a better method is to have them act as a negative air machine (or NAM) to suck the spores, trap them in a filter, and properly exhaust anything left through ducting to the outdoors.  It’s not enough to remove the mold, the spores in the air need to also be removed to ensure a healthy environment.

  1. Not addressing the moisture source

The third issue, which seems to be a no-brainer, is to address and fix the moisture problem that initially allowed the mold to grow.  It seems obvious, but I have seen it more than once or twice.  The homeowner has paid thousands of dollars to have remediation performed, but will have the exact same problem in a year or two because the moisture source that created the mess, to begin with, was never addressed.  Fix the moisture source!

So for review, if you ever have remediation performed on your property, keep in mind these three objectives:  1.) Physically remove the mold.  2.) Properly clean the air of mold spores.  And finally 3.) Fix the moisture source that caused the problem to begin with.  Then you can be assured that the problem has been fixed once and for all.  

Microbiomes, Buildings, and Human Health

An informative report was published by the National Academies of Sciences, Engineering, and Medicine. The report highlights how a building can influence changes in the microbiology inside the building which can impact human health.  In this blog post, I summarize some of the key points from the consensus study report.  
It may be helpful to keep the definition of microbiome in mind when reading this post.  A microbiome is defined by Merriam-Webster as “a community of microorganisms (such as bacteria, fungi, and viruses) that inhabit a particular environment.” Popular press commonly describes the microbiome of the human body, but buildings also have a microbiome.

The report points out that damp, water-damaged buildings can provide the right environment for microorganisms to flourish.  These organisms can have adverse effects on the human respiratory system.  This problem is exasperated in poorly ventilated buildings.  Currently, many well-sealed homes do not introduce much outdoor air besides through the occasional open window.  Mechanical ventilation can help introduce outdoor air into a tight building.  The report argues that having controlled, mechanical ventilation to introduce outdoor air is preferred over infiltration through cracks, crevices, gaps in openings for pipes, or other unintentional pathways.

It makes sense that ventilation can impact indoor air quality which can then affect human health.  However, the report points out that even water temperature in plumbing systems can affect the viability of microbes which can then impact human health.  Clearly, there is more than one aspect of a building that can impact people but the report does highlight a few means to better monitor microbes in a building.  Sensors that measure temperature and humidity can help monitor the dampness of a building which can inhibit microorganism growth.  Sampling of different microbes in a building can also be done to get a better understanding of microbes that can adversely impact humans.  However,  few organisms can be cultured which can make it difficult to get accurate information about a building.    The sampling methods of the future are through genomics, proteomics and other advanced laboratory procedures that can provide more data about the microbes living inside buildings.

A link to the report can be found here:

Bio-Contaminants in Water-Damaged Buildings

[The following is a chapter I submitted for a workshop on water damage, with a target audience of property managers.  It is a good primer on the contaminants found during water damage.]


Microorganisms are all around us.  In fact, they are in and on our bodies as well!  The vast majority of these organisms are harmless to humans, with many even having beneficial effects.  The human cells in your body are outnumbered by the bacterial cells in your body 10 to 1.  And some speculate that your human cells are outnumbered 100 to 1 when compared to viruses.  These mostly good microorganisms help our bodies function and are often referred to as our “microbiome”.


Even buildings can have a microbiome.  Normal types of bacteria and fungi are found in the air, dust and surfaces throughout.  Many of these microorganisms are normal and expected to be found in homes, offices, schools and other buildings. However, when water damage occurs, the indoor microbiome can change and have a negative effect on health.  


This chapter will describe the three most important microorganisms: fungi (mold), bacteria and viruses.


Fungi (Mold)

Mold belongs to the taxonomic kingdom of fungi. Fungi are not plants because they are unable to make their own energy via photosynthesis.  That means fungi don’t need light to grow.   Besides mold, other fungi include mushrooms and yeast. Fungi is a scientific term, whereas “mold” is more of a layman’s term.  Mildew is a term with several disparate definitions but is essentially the same thing as mold.


There are over a million different species of fungi with an estimated 30,000 types of mold. Mold gives off tiny spores, which are similar to plant seeds.  Once these spores land on ideal environmental conditions, they can grow into a colony (similar to how a seed grows into a plant).  Mold spores are ubiquitous in outdoor and indoor air, but because they are microscopic, you cannot see them.  They are typically about 2-10 microns in diameter, which is about 10 times smaller than the width of a human hair.  Even a normal home, office or school will commonly have more than 1,000 spores per cubic meter.


What do mold spores need in order to grow?  There are two primary environmental conditions: nutrients and moisture.


Mold needs nutrients to grow.  Just like there are enzymes in our digestive tract to break down food, each mold species has unique enzymes too.  Because of their enzymes, some molds prefer to grow on leather, whereas others prefer to grow on paper, leaves, drywall, soil, dust, or other organic materials.  Mold can grow in every building because the indoor environment is filled with organic materials.  Mold can even grow on an inorganic surface such as concrete by using nutrients from the paint or the dust accumulation on the surface.


Mold also needs moisture to grow. When organic materials are dripping wet, mold can certainly grow.  But what about environments where there is no liquid water, just high humidity?  There is a wide variety of humidity preference between the different species.  Relative humidity (RH) is used to measure moisture in the air and “equilibrium relative humidity” (ERH) is used to describe moisture within a material or substrate.  When a substrate such as drywall is in a room with 80% RH, it will generally approach an ERH of 80%.  Surfaces above 60% ERH are at risk for mold growth, but the vast majority of species require an ERH above 80%.


When a spore lands on a surface with the right nutrients and moisture, it will germinate, grow into a colony, and give off more spores.  That can happen as quickly as 24-48 hours for some species when conditions are ideal.  Therefore, it is important to dry materials quickly.  If mold grows but then dries out, it will stay dormant until more moisture comes back.  If the surface is dry for long enough, the colony and its spores will eventually die.  However, dead mold is still potentially allergenic and toxigenic.


The primary health concerns about mold are allergy and respiratory symptoms, such as asthma and cough.  Although there are no reliable numbers, it is estimated that about 15% of the US population has an allergy to at least one mold type.  Beyond these effects, mold can cause infections in immunocompromised individuals. These rare infections may happen in a hospital or nursing home, but some fungal infections can affect even healthy individuals (e.g. Valley Fever).  The most controversial effects of mold are the mycotoxins that some species can produce. The toxins are not released as a gas but are present on the colony and travel on the spores. There is a wide range of opinion regarding the exact effects of mycotoxin inhalation. Lastly, there are musty odors produced during growth that also have an effect on human health, although the effects are not well understood.


Although there are many species of mold, there are a few common types of which it is important to be aware. The following are water damage indicators which are uncommon in normal buildings, but common where there is chronic dampness:

  • Stachybotrys (sometimes referred to as “black mold” or “toxic mold”)
  • Chaetomium (pronounced K-toe-me-um)
  • Ulocladium
  • Fusarium
  • Trichoderma
  • Acremonium



Furthermore, some species of the following types can indicate water damage:

  • Aspergillus
  • Penicillium
  • Cladosporium




Bacteria belong to an entirely different kingdom than mold.  Their cells are unique in that they lack a nucleus.  Unlike other organisms, bacteria can be found in extreme environments from the tops of mountains to the bottom of oceans.  Although it is estimated that there are over 10 million species of bacteria, the vast majority do not cause human illness.  


The following are examples of building-related diseases caused by bacteria:

  • Legionnaires’ Disease
  • MRSA
  • Tuberculosis
  • Digestive tract and respiratory disease from fecal bacteria


With water damage, the primary concern is fecal bacteria, which are those species found in sewage.  Pathogenic fecal bacteria include:


  • Escherichia coli
  • Enterococcus
  • Fecal Streptococcus
  • Clostridium difficile
  • Leptospira
  • Helicobacter pylori


Besides the risk of infections from these fecal bacteria in sewage, certain bacteria produce endotoxins.  These toxins are found in the cell wall of Gram-negative bacteria, which can be commonly found in sewage.  When breathed in, endotoxins can affect respiratory function.  It is important to note that even when Gram-negative bacteria are killed, their endotoxins may not be diminished.  Therefore, it is critical to clean flood-damaged areas, not just use disinfectant.  


When areas are impacted with sewage, it is important to verify that fecal bacteria has been properly removed prior to reoccupancy.  The highest standard is to check surfaces for DNA related to fecal bacteria.  Culture plate methods may provide a “false negative” because the remnant, dead bacteria doesn’t grow on a petri dish (although its DNA could be detected).  Performing clearance testing puts people at ease when re-occupying a room impacted by raw sewage.



Viruses are the most unique microorganisms to be found with water damage.  Viruses do not have the means to reproduce by themselves.  They invade cells and commandeer the machinery to reprogram the cell to produce more viruses.  They can be 100 times smaller than a single bacteria cell as they generally range in size from .02 – 0.4 microns in diameter.  


There are a few pathogenic viruses associated with water damage:

  • Hepatitis A
  • Enteroviruses
  • Norovirus
  • Rotavirus

Viruses are very difficult to measure, so their impact on sewage-damaged properties is not fully understood.

Assessment and Remediation

When there is water damage, it is common to hire an industrial hygienist to assess environmental concerns before and after the remediation process.  The industrial hygienist can perform several functions, including:

  • Confirm mold growth or presence of other organisms
  • Identify the types present
  • Investigate the underlying moisture source
  • Determine the extent of the problem
  • Develop a scope of work for the remediation contractor to follow
  • Perform clearance testing when remediation is complete to verify the work was successful

Some states require that an assessment is performed both before and after remediation by a party independent from the contractor.  Although Illinois does not have such a requirement, it is still a good idea.


When selecting an industrial hygienist to assess biological contamination, look for certifications such as the Certified Industrial Hygienist (CIH) which has the most rigorous education, experience, and testing requirements.  Other acceptable certifications are from the organization American Council for Accredited Certification (ACAC).  Experience and knowledge are also important factors when selecting an industrial hygienist, as not everyone has a specialty in biological contamination.  



It is important to act quickly when there is water damage.  Delays can turn a small water problem into a large mold project.  If a water loss leads to biological growth, it is advisable to hire an industrial hygienist to evaluate the problem prior to remediation taking place.  Mold and sewage problems must be taken seriously as sensitive individuals may experience symptoms from the exposure. Being proactive can quickly resolve an issue that might otherwise lead to a drawn out lawsuit.

Vermiculite and Asbestos

You may have come across something called “vermiculite” in potting soil or in attic insulation.  Why is it often associated with asbestos?

Vermiculite is a mineral that appears in a pebble-like form. It is often gray, silver, and gold in color and can shimmer in light. Because of its insulating properties and versatility, vermiculite was used in a wide variety of purposes such as insulation and potting materials. While vermiculite alone isn’t harmful, it can often contain asbestos.

The bulk of vermiculite found in US homes is directly from Libby, Montana. The EPA estimates that 70% of vermiculite sold between 1919 to 1990 originated from there. In the vermiculite mines, there was an asbestos deposit that formed alongside it. As the mineral was mined, large quantities of asbestos fibers were thrown into the air which caused many properties of Libby to become contaminated. While some of the asbestos content in Libby is regulated fibrous Tremolite, many of the asbestiform minerals found are known as Libby amphiboles, which are not regulated.

The term Libby amphiboles refers to two asbestiform minerals known as Richterite and Winchite. These minerals typical form from contact metamorphism of limestone. In their fibrous forms, they share similar physical properties to the regulated five amphibole asbestos minerals. There are no current federal regulations on Libby amphiboles although they may have similar health effects to other regulated types.

The EPA has spent hundreds of millions of dollars on the cleanup of Libby.  They recommend that if you find suspected vermiculite insulation in your home, you should assume it to be asbestos-containing. There are tests that can be performed, but they are more expensive than standard asbestos testing.  


Mold Clearance Testing

One of the key parts of an effective mold remediation project is one that is often overlooked. “Post remediation verification” (PRV), or “clearance” is the process that evaluates the performance of a mold remediation project. This step should always be done by an unaffiliated, third-party testing company to assure an unbiased assessment. This assessment is so important that some states require it by law.  It is also key that this assessment is scheduled at the proper stage in a remediation project. A verification assessment should be done after all of the mold has been removed, but before the containment has been removed, antimicrobial coatings have been applied, and build-back of the building materials.

The specific steps taken for a post remediation verification assessment are dependent on the specific mold remediation project, however a few basic steps should be followed: assessing the containment, visual inspection for remaining mold growth or mold damaged materials, verifying there are no musty odors present, and checking that the work area is clean.  Although there is no consensus on sampling for clearance, air samples are commonly collected to see if the levels in the air have been returned to background amounts.


We occasionally get calls from clients who have been told by their remediation company NOT to have a post remediation verification inspection done. They typically say it is a waste of money.  These unscrupulous companies don’t want anyone to review their work because in our experience even the best companies often miss things. You can imagine what might be missed by companies who like to cut corners! In our experience, we find something that was missed in about 50% of all post remediation verifications. This can range from small areas of missed growth or a slight elevation of airborne fungal levels to large issues like major moisture problems and mold damaged materials remaining in place.


The key goal of a mold remediation project is to return the affected areas to a “pre-loss state”. This can help avoid future issues from a problem you thought was already addressed.  One of the most compelling reasons to have PRV testing done is to provide a “clearance letter”.  This is a document you can share with the future purchaser of your home when disclosing the past mold problem.  Having an independent evaluation determine that the project was successful can put everyone’s’ mind at ease.  For all these reasons, we strongly recommend having a post remediation verification assessment done.

Radon Part III – When Radon Hits Home

In my recent blogs, I have written in some detail about radon and how it can affect your health.  But just recently, I had a call from my brother who was concerned about the possibility of radon in his home.  When talking with a next door neighbor who was selling his home, he discovered that the neighbor had elevated levels of radon.  Naturally, my brother was curious about his own home and called for my expertise.

The radon levels for a residential property should be under 4.0 pCi/L.  Picture both my brother’s and my surprise when we tested his home and discovered that it was between 26 and 27 pCi/L!!  Yikes!!

Needless to say, my brother called a professional to install a mitigation system.  A mitigation system usually involves drilling a hole through the basement floor and installing a perforated pipe which has a fan continuously sucking the radon gas from the ground before it has a chance to enter into the living space.  The gas travels through a pipe that exhausts it outdoors where the gas mixes with ambient air and no longer poses as a safety hazard.

It was interesting to note that my brother’s neighbors on each side of his house had radon levels measuring roughly 10 pCi/L, but his home had an elevated level of 27 pCi/L.  There are several possible explanations for this.  One is that there could have been a larger store of uranium directly underneath my brother’s home.  Another explanation could be that my brother had recently installed new windows and extensive insulation; this worked at making his home more airtight and therefore made it more difficult for radon gas to escape.

Regardless of the reason, my brother is feeling much better about his situation.  After having a mitigation system installed in his home, I had the chance to retest his property.  The radon level had dropped from 27 pCi/L to  0.9 pCi/L.  Significantly better and much safer.

Website Review for “IDPH Guidelines for Indoor Air Quality”

The intention of this blog post is to review a website from the Illinois Department of Public Health (IDPH).  The website can be found here:

The website provides some general guidelines for indoor air quality.  Some details about each parameter are discussed.  Parameters ranging from humidity and temperature to formaldehyde and particulates in the air.  It also provides a table that summarizes the guidelines for the following parameters from four different agencies, including IDPH:

  • Humidity
  • Temperature
  • Carbon dioxide
  • Carbon monoxide
  • Hydrogen sulfide
  • Ozone
  • Particulates
  • Formaldehyde
  • Nitrogen dioxide
  • Radon

The “IDPH Guidelines for Indoor Air Quality” website gives recommendations for improving indoor air quality.  Proper thermostat location along with HVAC maintenance are a few of those recommendations.  Source control is also mentioned.  It is generally better to remove the source of contamination, rather than trying to filter it out or dilute it with ventilation.  The problem is often hunting down the source.

Additionally, the site provides contact information for other agencies and groups that offer educational information related to indoor air quality.  National Institute for Occupational Safety and Health (NIOSH), Illinois Department of Labor, and Occupational Safety and Health Administration (OSHA) are mentioned.

Towards the end of the website, a bullet list of recommendations for indoor air investigations is provided.

This site does not provide a lot of detail but it does cover a large scope of information related to indoor air quality.  Indoor Science follows many of the items covered by the IDPH website when doing an investigation for indoor air quality contaminants.  If you have any concerns please feel free to reach out to us at (312) 920-9393.  

Asbestos in Settled Dust


In homes throughout the nation built before the 1980s, asbestos containing materials were commonly incorporated. Asbestos was used because of its high durability, fire resistance, and other favorable properties. Asbestos was used in drywall, plasters, floor tiles, HVAC insulation, plumbing insulation, adhesives, and many other products. Asbestos containing materials in the home become a health risk when they are damaged, disturbed, and made friable, which releases the asbestos fibers into the air. Typically asbestos fibers can remain airborne for up to 72 hours in area of low air movement, afterwards falling to the surface and generating dust.


The larger the release of fibers from asbestos containing materials, the more dust it generates once the fibers settle. As a mineral, asbestos can remain in the dust indefinitely and does not degrade. If an asbestos containing material was improperly abated in a home, this could lead to the settled asbestos dust being disturbed in the future.


Unlike asbestos air testing and inspections, there are no federal or state regulations on settled dust sampling. The bulk of our understanding on asbestos dust is based off of industry guidelines. The method we use at Indoor Science for dust sampling is called TEM Microvac. This process involves taking a filter cassette and attaching it to a high volume air pump, which sucks dust onto the filter.  We generally collect dust from a 100 cm2 area. The cassette is then analyzed at an accredited laboratory by an electron microscope which can scan the cassette and identify the amount of asbestos fibers found. This method is called TEM, which stands for Transmission Electron Microscopy).  


The laboratory reports the results as asbestos structures per square centimeter.  As previously stated, there is no governmental regulation for a permissible amount of asbestos fibers in the dust.  Nevertheless, there are industry guidelines that help us interpret if the fibers found in the dust are background levels, elevated, or highly elevated.


If you have concerns about settled asbestos dust in your home. Feel free to contact us.

Featured Mold – Cladosporium

Cladosporium is the most common culturable mold genera found in the world(1,2), found anywhere from the Amazon to the Arctic. Cladosporium grows in colonies that are dark in color, ranging from black/brown to green. In the outdoors, Cladosporium commonly grows on decaying plants and soil. Cladosporium levels in the outdoor air vary greatly by season, with very high numbers in the summer, and low numbers in the winter.  Indoors, this fungi is a type that we see in areas with chronic high humidity, such as a poorly ventilated bathroom, or a damp basement. If you have ever seen the dark stains along the grout lines in a shower, in my experience, that is most likely Cladosporium.

When sampling the air for mold, Cladosporium levels are often difficult to interpret indoors because it naturally occurs in the outdoor air at high levels. A major limitation of the most common air sampling technique is that it only identifies the genus, such as Cladosporium, but is unable to identify the species, such as Cladosporium sphaerospermum.  The overall levels of Cladosporium in the outdoor air and indoor air may be similar, however the Cladosporium indoors may be a different species. Since spore trap sampling can not identify Cladosporium to the species level, this could result in a “false-negative” interpretation.

Cladosporium is not thought of as being a pathogenic or a toxigenic fungi. However, like all molds, it can cause allergic reactions in sensitive individuals as well as being an asthma trigger.

  1. Hedayati, M.T., Mayahi, S., Aghili, R., Goharimoghadam, K. (2005). Airborne Fungi in Indoor and Outdoor of Asthmatic Patients’ Home, Living in the City of Sari, Iranian Journal of Allergy, Asthma, and Immunology, 4, 189-191.
  2. Shelton, B. G., Kirkland, K. H., Flanders, W. D., & Morris, G. K. (2002). Profiles of Airborne Fungi in Buildings and Outdoor Environments in the United States. Applied and Environmental Microbiology, 68, 1743–1753.

Radon: Part 2!

One of the happiest days of one’s life can be when you purchase your first house (or upgrade to an even better one)!!  But let’s face it, there are several things to worry about before the big moving day.  In addition to all the paperwork, we practice due diligence and hire a home inspector.  And if we are really on the ball, we get the home tested for radon.  The EPA recommends that the concentration (measured in pCi/L) should be below 4.0.  You get the test done, and lo, your readings are below 4.0 pCi/L.  Hooray!  Time to move in and never, ever worry about radon in your home again.

But what if that is not the case…  When a radon professional performs a test inside a home, the minimum test duration is 48 hours.  But that is just a snapshot in time.  Radon levels can and do fluctuate from day to day and from season to season.  Radon levels during the winter can be elevated because the buildings are closed up.  In addition, more people are exposed because they are spending more time indoors.

An increase in levels can also occur due to home renovations.  Let’s face it, everyone wants an air tight home.  We install new windows, add weather stripping and insulation in older houses.  These things help make our homes more comfortable and even save money.  But these items can also seal up our house and greatly limit the avenues for radon gas to escape.  These improvements can trap radon in our home.  Add to that temperature and pressure changes and your radon levels can easily exceed the 4.0 pCi/L.   

Its also important to note that as a home ages, you can also have an increased number of cracks in the floors.  This can happen as the house settles.  Negative pressure can suck up radon gas from the new cracks and elevate the radon levels in the building.   

So how do we respond to this and know for certain that the levels are safe?  The simple answer is “periodic testing”.  Many experts recommend testing during the winter when radon levels can be elevated.  After making any improvements to your home, which can include finishing a basement, it is generally a good idea to retest and check the radon levels.  Keep in mind that it is typically very easy to remediate radon in a house from a technical standpoint.

So go ahead and celebrate that new home – but beware!!  A single radon test does not a safe home make.  Be sure to test periodically during different seasons and when doing anything related to improving the energy efficiency of the home.   Not only will you have purchased a wonderful home, but you will have also purchased piece of mind.  

What Is Radon?

“So what exactly is radon?  Is that bad for you?”

I was asked these questions recently and it struck me how little the general public seems to know about this insidious gas.  In my experience, there is a greater understanding of radon today then there was roughly 20 years ago.  However, I believe that there still needs to be a greater understanding of radon and the threats that can be associated with it.

First off, what is radon?  Radon is a colorless, tasteless, and odorless gas which is naturally occurring in the soil and is part of the radioactive decay chain of uranium.  It is naturally occurring and found in the ground at varying concentrations worldwide.  It gets indoors through cracks and openings, found especially in rooms at or below the ground surface.  For single family residences, this includes basements and rooms above crawl spaces and slab foundations.  

Now the bad part.  What does this mean for your health?   Radon is a known human carcinogen; it is the leading cause of lung cancer in non-smokers, and the second leading cause of lung cancer overall.  This has been proven through epidemiological data and laboratory evidence.  According to the Environmental Protection Agency (EPA), “Radon is responsible for roughly 21,000 lung cancer deaths every year.  Roughly 2,900 of these deaths occur among people who have never smoked.”.  (  

The EPA and Illinois Emergency Management Agency (IEMA) Action Level for radon in a property is at or above 4.0 pCi/L (picocuries per liter of air) during a testing period lasting at least 48 hours.  How prevalent are elevated radon levels in the state of Illinois?  The University of Illinois reported that “Professional radon measurers have found over 41% of Illinois homes tested at or above the recommended action level of 4 picocuries per liter of air.” (

What is the best way to know if you have elevated radon levels in your home?  Testing is overwhelming the best way!  A radon professional will be able to provide the most accurate numbers for your home or commercial business.  If you have any concerns regarding radon, feel free to contact Indoor Science at 312-920-9393.  

Is That A Cat Skeleton?

For the past three months, I have spent several days a week crawling on my hands and knees (and occasionally on my stomach), wearing a Tyvek suit, a respirator, gloves and lugging equipment underneath unlit residential buildings. What was the purpose (besides building character)?  To help clients of ours assess mold and water issues in several of their properties’ crawlspaces. Somehow I was designated to be- “crawlspace guy.”

Fungal growth

Besides the physical challenges of navigating through the crawlspace, the inspections themselves became very straight forward.  The majority of any water damage issues and subsequent mold growth were associated with plumbing problems.  Broken pipes, missing pipe caps, and condensation on uninsulated pipes were all very common.  All of these plumbing issues introduced water into the crawlspace causing fungal growth with varying degrees of severity.  In a few properties I even saw large fungus growing on structural components of the building!  Some crawlspaces had minimal mold growth that could easily be wiped away, while other crawlspaces will require the complete replacement of material such as joists or subflooring not to mention major plumbing repairs.

More Fungal Growth

Dead cat?

Although I was hoping to find a pot of gold hidden in one of these crawlspaces, all I found was broken glass, rusty nails, garbage, skeletal remains of different critters, old Old Style beer cans, and rats in various states of existence.  At least I’ll sleep well knowing that we helped improve the air quality for many clients.


Joel Silva

The Basics of Legionella


File:Legionella Plate 01.png

Legionella bacteria can pose a serious health risk in the indoor environment. Legionella is a gram-stain negative bacteria that was discovered in 1976 after an outbreak in Philadelphia. The outbreak occurred at an hotel during a convention for the American Legion, where 34 died and hundreds were hospitalized.  Up to that point in time, the bacteria was not discovered or named.


Legionella can be found naturally in freshwater environments as well as in man made water systems such as cooling towers, water tanks, and decorative fountains.  It typically forms in warm, stagnant water and spreads when that water becomes aerosolized. It can form two different types of infections in humans:the more severe Legionnaires’ disease and the milder Pontiac fever.


Legionnaires’ disease is a type of pneumonia, which is typically more fatal than a common pneumonia. Exposure occurs when Legionella contaminated water is aerosolized and then inhaled by a person. Symptoms of Legionnaires’ disease include cough, high fever, shortness of breath and wide variety of symptoms similar to pneumonia. The infection is typically treated with antibiotics. The people who are most at risk for Legionnaires’ disease are smokers, elderly and the immunocompromised.


Another infection caused by the Legionella bacterium is Pontiac Fever. Pontiac Fever is a condition that resembles influenza, and is a Legionella infection that does not include a form of pneumonia. It was discovered retrospectively after the Legionnaire’s disease outbreak of 1976 when blood samples from a 1968 influenza outbreak in Pontiac, Michigan showed the presence of the Legionella bacterium. Pontiac Fever is treated with antibiotics like Legionnaires’ disease. Both Legionnaires’ Disease and Pontiac Fever are generally not spread from person to person.


If you are concerned that your water systems are contaminated with Legionella, consider hiring a consultant such as Indoor Science to do an assessment of your property.

Pesky Particles

The term particulate matter refers to the combination of liquid or solid particles that are present in the air. The size of particles varies with some types being visible to the unaided eye while others are only visible through microscopy. These particulates can originate from a wide variety of sources, such as combustion, the breaking apart of larger materials,  the wind blowing particles from settled dust, and a myriad of other sources. In recent decades various agencies and officials have linked elevated particles to having a negative impact on indoor air quality and health.


Particulate matter with a 2.5 micrometer aerodynamic diameter or smaller may pose special health risks and are monitored by the EPA. Particles of that size are respirable and are not removed by the lungs’ mucus and cilia. Exposures to elevated fine or ultra-fine particulates can lead to negative health effects such as heart attacks, reduced lung function, asthma, and various pulmonary issues. Elevated particulate matter in outdoor air can cause environmental issues such as reduced visibility, acid-rain, and damage to ecological systems.


Indoor Science recently had a project where construction dust from one condo unit caused an extremely high level of particles in the neighboring unit.  If you are concerned about particulate matter affecting indoor air quality at your property, please contact Indoor Science to assess the situation.


PAACB Certification

Laboratories who analyze samples for mold typically have accreditation from the AIHA (American Industrial Hygiene Association) Laboratory Accreditation Program, LLC. This accreditation is for the lab as a whole covering everything from the facilities, equipment, standard operating procedures (SOP), and even record keeping. What may be surprising to some is that this accreditation does not cover the qualifications and proficiency of the analysts. For that, there is only one certification available: Pan American Aerobiology Certification Board’s (PAACB) Spore Analyst Certification.

The Pan American Aerobiology Association (PAAA) realized the importance of individual competency when it came to fungal analysis, so they coordinated the creation of the Pan American Aerobiology Certification Board, commonly known as PAACB. This group oversees the certification of individual analysts for fungal spore identification. This is the only certification currently available that covers the proficiency of the individual analyst. The certification is made up of two exams which cover everything from basic mycology to fungal spore identification and enumeration.

PAACB is globally recognized certification to demonstrate the proficiency of the individual. PAACB certification is actually recognized by the State of Texas as qualification for receiving a Mold Analysis Laboratory License. There are certified analysts in many different commercial labs and agencies as well as individual persons who have achieved this certification. Indoor Science has a certified analyst on staff who handles many of our mold samples in our in-house lab. We also have the unique ability to take the microscope and analyst on the project site for on-site analysis of mold samples for the fastest possible turnaround time!