Frequently Asked Questions


What causes mold to grow?

Why shouldn’t you attempt to kill mold with bleach?

How do you know if you have a mold problem?

What is causing that musty or moldy smell?

Do you have Toxic Mold, Black Mold, etc.?

What symptoms are commonly associated with mold exposure?

Why does the mold affect me, but not the other members of my family?

Who is at the greatest risk?

How do you prevent future mold growth?



1. What causes mold to grow?


Mold only requires oxygen, a source of moisture, and a substrate (food source) in order to grow. Mold can grow on almost any organic substance, but thrives on cellulose materials such as wood and paper products. Different types of mold require varying amounts of moisture and time in order to grow. Some molds, such as some Aspergillus species, can grow well within a 48 hour period and require a relatively low amount of moisture, while Stachybotrys chartarum requires a longer period of time and substantial moisture.



2. Why shouldn’t you attempt to kill mold with bleach?


When bleach is applied to mold growth a large percentage of the spores will become non-viable (unable to grow). You essentially have killed a large percentage of the mold spores. Unfortunately, a non-viable spore can cause many of the same allergenic health effects as a viable (able to grow) mold spore. The main difference between a non-viable spore and a viable spore is that viable spores can cause mold infections. Fortunately, most people (other than the elderly, young children, immunocompromised, etc.) are not susceptible to mold infections. However, many people are susceptible to mold allergens. Thus, applying bleach to mold growth is not protecting you from the commonly experienced health effects of mold. Even more importantly, an attempt to ‘wash’ mold growth off of a surface releases a larger percentage of the spores into the air, causing a greater magnitude of exposure. It is also important to note that bleach will not kill 100% of the mold growth, which may grow back if the source of moisture is not corrected.


The recommended way to rectify a mold problem is to physical remove all porous materials that contain visible mold growth, correct the source of moisture, and to ‘clean’ all areas affected by primary and secondary contamination. Removal should take place in accordance with the IICRC S520 – Standard and Reference Guide for Professional Mold Remediation.


3. How do you know if you have a mold problem?


A building that contains areas of extensive mold growth should be assessed further. Small areas of mold growth could be minor problems, but could also be evidence of a more wide spread ‘hidden’ mold problem. For instance, a finished basement that has small areas of mold growth on the drywall could mean that the foundation is experiencing moisture intrusion. This moisture intrusion could cause extensive mold growth on the backside of the drywall, which would not be visible. The same situations are also commonly found around leaking windows and doors.


Furthermore, if areas of the building smell musty, even if there is no visible mold growth, the building could potentially have a hidden mold problem, especially if the building has a history of flooding.


4. What is causing that musty (moldy) smell?


Musty smells are usually caused by Microbial Volatile Organic Compounds (mVOC’s). mVOC’s are gas-phase metabolites produced by growing mold. This type of smell is usually associated with a mold problem (visible or hidden). ZWS would conduct an inspection and moisture assessment (thermal imaging) to identify problem areas.


5. Do you have Toxic Mold, Black Mold, etc.?


The terms Toxic Mold and Black Mold were invented by the media. Toxic Mold basically means a mold that produces mycotoxins. Mycotoxins are metabolic byproducts that mold produce when they are growing. Mold produces these mycotoxins as defense mechanisms toward other competing organisms. The most publicized mycotoxin producer is Stachybotrys chartarum, but there are many others. Not all mycotoxin producers are extremely harmful, nor is every non-mycotoxin producer completely safe.


The term Black Mold originated because some mycotoxin producers grow black in color. However, many common types of mold growth are also black in color. Therefore, color should not be a determining factor when assessing a mold problem.


Mycotoxin producers are potentially harmful, but the exact mechanisms of how they affect the human body are poorly understood. Some mycotoxins, such as Aflatoxin B 1, are considered a carcinogens (cancer causing agent), but little is known about exposure limits. The American Industrial Hygiene Association (AIHA) states, “… the confirmed presence of Stachybotrys chartarum, Aspergillus versicolor, A. flavus, A. fumigatus, and Fusarium moniliforme requires urgent risk management decisions to be made…”


6. What symptoms are commonly associated with mold exposure?


The most common health effects caused by mold exposure include mucous membrane discomfort (eye, nose, and throat irritation), rhinitis (runny nose), headache, fatigue, and upper respiratory tract problems. Often the symptoms will reduce, or completely subside, when the person leaves the affected building.


When dealing with young children, or elderly individuals, additional precautions should be taken. This is because a child’s immune system is still developing, and an elderly person’s immune system is declining. For children, prolonged exposure to elevated concentrations of mold spores may be a cause of asthma. In fact, asthma is the most common chronic illness among children in the United States. A child who develops asthma at an early age will most likely feel the effects for life.


More severe health effects associated with mold exposure includes hypersensitivity pneumonitis (HP).


HP is an immunologically-mediated reaction to specific biological antigens from plants, insects, bacteria, and fungi (mold). Acute HP develops 6 to 12 hours after a relatively high-intensity exposure, and is marked by symptoms including shortness of breath, cough or fever… The symptoms abate within a few hours to 1-2 days, and tend to recur with each exposure. Only those individuals who are immunologically sensitized to the particular antigenic agent of exposure become symptomatic; thus, among groups of workers with similar exposures, only a small percentage are actually at risk of developing HP.


IICRC S-520 (p. 43)


Lastly, repeated elevated exposure to an allergen, such as mold, will eventually cause many people to become sensitized to that allergen. After a person has an allergen sensitivity, it will no longer take an extremely elevated exposure to get the same adverse health effects.


7. Why does the mold affect me, but not the other members of my family?


Individuals have different sensitivities to mold allergens. If one family member is sensitized, slightly elevated levels of mold spores may trigger a reaction, while the other family members are virtually unaffected.


8. Who is at the greatest risk of mold?


Individuals at the greatest risk are people with compromised immune systems (HIV positive, organ transplant patients, etc.) children (undeveloped immune systems), and elderly (declining immune systems). Not only are these three groups susceptible to the allergenic effects of mold, but they are also more susceptible to mold infections. These infections include mycoses (invasive aspergillosis) hypersensitivity disorders (i.e. allergic broncopulmonary aspergillosis), and can be life-threatening in very severe cases.


9. How do you prevent future mold growth?


Prevention of mold growth is surprisingly simple. Controlling the moisture in your home will prevent mold from growing. Here are a few easy steps.


Keep the relative humidity in your home under 50%.

If you experience a major water loss, immediately contact ZWS and a qualified water restoration company.

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Appleton, WI 54913


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