Understanding the Basics of Mold Testing

Mold is everywhere and plays a critical role in nature by breaking down organic matter. It also has the ability to break down and remove certain pollutants from the environment. Mold has been featured in the medical realm as an ingredient for many antibiotics and medicines, including penicillin, the first ever true antibiotic. 

Albeit these positives, mold can cause a host of severe health problems, mainly when it thrives indoors. Worse, mold only takes 24 to 48 hours to grow and spread. That’s why it is crucial to have your home tested for mold by a professional whenever you suspect an infestation. 

Mold testing is necessary for assessing the presence of mold in indoor environments and the extent of infestation. Whether you have concerns about the health implications of mold or want to sell your property, mold testing is an integral part of creating and ensuring a safe living environment. This post will cover more about mold testing, emphasizing the mold testing steps and interpretation of results. 

Understanding Mold

A natural part of the environment, mold is a living eukaryotic organism that has evolved to eat waste and dead materials. It can be found anywhere and can be harmful as it is beneficial, depending on the species. Mold often grows and spreads on damp or decaying organic matter but can be found anywhere there is moisture and oxygen. 

Excessive moisture is generally the cause of indoor mold growth. After growing, they spread by producing tiny reproductive cells called spores that float through the air until they land in other locations. That’s why no space is completely free from mold spores, not even surgical operating rooms. As a result, mold exposure is unavoidable. 

A picture of indoor mold.

While there are thousands of species of mold, the cause of concern is Stachybotrys chartarum, commonly known as “toxic mold” or “black mold.” Albeit rare, this species produces high levels of mycotoxins that can be hazardous. All in all, any species of mold can be a health hazard if allowed to grow out of control. 

Tip: Indoor mold, whether it is Stachybotrys chartarum or another species, indicates a problem with water and moisture. That’s why EPA recommends you clean and dry any damp or wet surfaces to prevent mold growth. 

Why Indoor Mold Is a Serious Concern

When organic matter dies, molds like Aspergillus, Mucormycetes, and Alternaria grow on them and physically eat them. Like other organisms, they produce waste after eating the dead organic matter, which can be harmful. With most homes being air (insulting homes to make them energy efficient creates air-tight space), these potentially harmful toxins are trapped indoors. The limited ventilation also means more moisture trapped, creating ideal conditions for mold to thrive. 

Even in a few days, mycotoxins can quickly build up, which can cause serious health problems. Some of the health risks associated with indoor mold growth include:

  • Asthma attacks
  • Sneezing
  • Skin rashes
  • Headaches
  • Dizziness
  • Red eyes
  • Runny noses

In extreme cases, mycotoxins can cause neurological problems and, worse, death. The health risks are especially harmful to children, elderly people, and persons with pre-existing respiratory issues. 

Mold Testing for Homes

Indoor mold is widespread and usually appears like stains that can be in a range of colors. Where there is no visible growth, a musky smell can be an indication that you have mold. 

If you suspect that you’re dealing with mold, it is good to have your home assessed for the presence of mold immediately. It is time to get your home tested for mold if you:

  • See visible mold growth
  • Smell musty odors
  • Have or suspect water damage
  • Have suffered flooding or leaks recently
  • Experience health problems

Notably, while you can test for the presence of mold using a DIY mold testing kit, home testing kits are often inaccurate and are known to produce a large number of false positives. That’s why it is always recommended to hire mold testing professionals. 

A professional testing mold.

Types of Mold Testing

There are several mold testing methods suited for different situations. Here are some of the common methods mold testing professionals use: 

1. Air Sampling

As the name suggests, this method involves the mold expert collecting air samples from your home or office. The samples are collected from different areas of your home or office, and a control sample is taken outside the building. Collected samples are then taken to a laboratory for analysis. 

When done properly, air sampling can help determine the types of mold present in your home and the concentration of mold spores in the air. This method is also useful in detecting airborne contaminants present in your home. 

2. Surface Sampling

Surface sampling involves taking samples from areas where mold is suspected to be growing and sending them to a lab for analysis. It can effectively determine the type of mold in your home but not the concentration levels. Because it can’t accurately determine concentrations of harmful mold spores and other airborne contaminants, surface sampling is best used as a basis to determine whether or not further action is needed. 

3. ERMI Mold Sampling

Environmental Relative Moldiness Index (ERMI) testing, also known as DNA mold testing, is a comprehensive approach to mold testing. It involves collecting multiple samples from different locations throughout the home and sending them for analysis. When done correctly, it gives more accurate results. 

4. Bulk Sampling

Often used where mold growth is visible, bulk sampling involves removing the material with mold or suspected to have mold and taking it for analysis. Like surface sampling, bulk sampling only determines the genus and species of mold present, not the concentration of harmful spores. 

Notably, lifting materials with mold should be done diligently to minimize the spread of potentially toxic spores. 

5. Lift Tape Sampling

As the name suggests, the tape is placed on areas with mold or suspected to have mold, then lifted and placed in a glass micro slide before they are sent to a lab for analysis. 

Notably, all other mold testing methods are often used as a basis to determine if there is a cause for concern. If mold is detected, air sampling is required to determine the concentrations of mold spores in the air. The analysis and interpretation give insights into the potential health implications of inhaling air in the room. 

A picture of a person holding a mold inspection report.

Do You Need Mold Inspection before Mold Testing?

Mold is everywhere, and while many molds are harmless, no one wants it in their homes. If you suspect mold, mold inspection is an important step toward getting your home spore-free. 

At its core, mold inspection is the process of assessing a home or any other facility to identify signs of the presence of mold. As such, it is majorly a visual inspection of a house. A good inspection starts with the inspector talking to the homeowner, tenant, agent, or property manager about their concerns and areas where they have seen mold or suspect mold is growing. The inspector will then comprehensively inspect the property, paying attention to any visible mold growth and musty odors. 

Some mold inspection technicians may use moisture meters and infrared cameras to detect moisture levels and mold presence, especially in hard-to-reach spots. 

If mold is detected, the inspector will try to locate the cause of excessive moisture and advise whether further testing is needed or if you should proceed with remediation. In most cases, testing is unnecessary if there is visible mold growth. 

What Can You Expect from a Mold Testing Professional?

A mold testing professional usually inspects your home for the presence of mold, collects samples, and sends them to a laboratory for analysis. A knowledgeable technician will also check for conditions that could lead to mold growth and advise accordingly. 

Once the samples collected from your home are tested, the inspector will provide a comprehensive report detailing the type(s) of mold present and their concentration. A good mold testing report should also include recommendations to address any issues. 

Reading and Interpreting Mold Testing Results

Truth be told, interpreting mold test results can be tricky unless you’re an expert in mold testing and remediation. It involves reading and understanding the different types of molds and spores concentrations as well as comparing indoor-outdoor spores concentrations. 

When it comes to interpreting mold testing results, homeowners need to understand that different types of mold are more hazardous. The risks different types of mold pose also depend on their concentration levels. To help you interpret mold test results with precision, here are basics details about some of the common types of mold: 

Penicillium and Aspergillus

These are the most prevalent types of mold and can be found anywhere. However, it is worth noting that indoor species are different from outdoor species. Regarding growth, Penicillium and Aspergillus grow and thrive with only humidity in the air as the source of moisture. They can even grow in clean environments, which makes them harder to eliminate, especially Aspergillus, which is more prevalent in the air. 

Indoors, these molds can grow and spread over surfaces such as clothing, leather, or building materials, particularly in moist areas. In large concentrations, they can lead to allergic reactions like skin rashes, coughing, and runny nose. People with pre-existing respiratory conditions may suffer lung or sinus infections from inhaling air with high concentrations of these molds. 


Found both indoors and outdoors, Cladosporium is an allergenic mold that often grows on wood, painted surfaces, and fiberglass. It is easy to notice because of its dark green or black velvety appearance. Acute exposure can cause asthma, runny nose, sneezing, coughing, skin rashes, and other allergic reactions. 

Stachybotrys (Black Mold)

Stachybotrys is a member of the large “black mold” category that thrives best on wet cellulose building materials. It is common on drywalls, insulation, and cardboard and can cause structural damage if allowed to grow beyond control. Regardless of the concentrations, this mold produces harmful mycotoxins, which can cause serious health problems. Exposure to Stachybotrys can cause respiratory infections, skin rashes, nausea, fatigue, and exacerbate other conditions. Acute exposures can even cause neurological problems and death in extreme cases. 


These molds are particularly produced by mushrooms and other fungi, so they are more common outdoors than indoors. Even better, they are not as allergenic, meaning they pose a minimal threat to human health. However, this doesn’t mean they are safe altogether. Basidiospores can cause structural damage and respiratory illnesses. 


Chaetomium is a fast-growing mold that thrives in wet areas and can be commonly found in water-damaged buildings. It produces mycotoxins, which can lead to respiratory issues when inhaled in larger quantities. It can as well damage buildings if left uncontrolled. 


Often found in the exact locations as the toxic Stachybotrys, Memnoniella is a mycotoxins-releasing mold that grows relatively faster. When allowed to thrive indoors, it can cause structural damage and allergic reactions.

If your mold testing results report a high indoor/outdoor ratio, mold is likely coming from a specific source inside your home. Regardless of the source, many types of molds will be cause for concern if they exceed the 500 sp/m3 mark. However, low concentrations of mold spores can be a health hazard, especially to people with pre-existing respiratory issues. That’s why it is important to eliminate mold growth in your home. 

In most cases, mold testing professionals recommend immediate remediation if you have mold. Remediation is an integral part of creating a safe and healthy living environment. Although it is nearly impossible to eliminate mold altogether, keeping your house clean and well-ventilated can help keep mold concentrations low. 

Need Mold Testing in Arizona?

Mold testing is an integral part of ensuring a healthy indoor environment. If you suspect mold is growing inside your house, a mold testing professional can help you rule out whether or not you have mold. G3 Environmental offers reliable mold sampling and testing services for homes and offices across Arizona.

No matter where you live in AZ we are here to help! Click your city to learn more: Phoenix Mold Testing, Scottsdale Mold Testing, Mesa Mold Testing, Chandler Mold Testing, Glendale Mold Testing, Gilbert Mold Testing, and Tempe Mold Testing.

In our commitment to safeguarding your family’s health and ensuring a safe working environment, we also offer Indoor Air Quality Testing and Asbestos Consulting. Our skilled team is a call away. 

Happy customers

Client testimonials

Julie S.


"They were very knowledgeable, answered all of my questions, excellent customer service and very professional."

Premier D.


"Jason and his crew are excellent! They handle all of our environmental testing and provide reports fast and sufficient. Always there if we need them!"

Chris R.


"Excellent service and price. Very thorough and they will not charge or suggest services you don't need."

Mike M.


"They were prompt and professional. From the time I contacted them until the time I had the full report was less than 36 hours."

Dorien L.


"Jason was just terrific. He went out of his way to accommodate my wish for an inspection as soon as possible. He went way about and beyond."

Braden C.


" Super reliable, friendly, and convenient! I definitely recommend Jason and his guys."

Ready for an inspection?

No matter your situation if you're dealing with asbestos, mold, lead paint or other harmful materials give us a call and we'll be on site fast to test.