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Molds are ubiquitous in nature, and mold spores are a common component of household and workplace dust. However, when spores are present in large quantities, they are a health hazard to humans, potentially causing allergic reactions and respiratory problems.

Some molds also produce mycotoxins that can pose serious health risks to humans and animals. The term "toxic mold" refers to molds that produce mycotoxins, such as Stachybotrys chartarum, not to all molds. Exposure to high levels of mycotoxins can lead to neurological problems and in some cases death. Prolonged exposure, e.g., daily workplace exposure, can be particularly harmful.

Symptoms of mold exposure

Symptoms of mold exposure can include:

  • Nasal and sinus congestion, runny nose
  • Eye irritation, such as itchy, red, watery eyes
  • Respiratory problems, such as wheezing and difficulty breathing, chest tightness
  • Cough
  • Throat irritation
  • Skin irritation, such as a rash
  • Headache
  • Sneezing/Sneezing fits

Health effects linking to asthma

Infants may develop respiratory symptoms as a result of exposure to a specific type of fungal mold, called Penicillium. Signs that an infant may have mold-related respiratory problems include (but are not limited to) a persistent cough and/or wheeze. Increased exposure increases the probability of developing respiratory symptoms during their first year of life. Studies have shown that a correlation exists between the probability of developing asthma and increased exposure Penicillium. The levels are deemed no mold to low level, from low to intermediate, from intermediate to high.[3]

Mold exposures have a variety of health effects depending on the person, some people are more sensitive to mold than others. Exposure to mold can cause a number of health issues such as; throat irritation, nasal stuffiness, eye irritation, cough and wheezing, as well as skin irritation in some cases. Exposure to mold may also cause heightened sensitivity depending on the time and nature of exposure. People at higher risk for mold allergies are people with chronic lung illnesses, which will result in more severe reactions when exposed to mold.

There has been sufficient evidence that damp indoor environments are correlated with upper respiratory tract symptoms such as; coughing, and wheezing in people with asthma.

Causes & growing conditions

Molds are found everywhere inside and outside, and can grow on almost any substance when moisture is present. Molds reproduce by spores, which can be carried by air currents. When these spores land on a moist surface that is suitable for life, they begin to grow. Mold is normally found indoors at levels that do not affect most healthy individuals.

Because common building materials are capable of sustaining mold growth, and mold spores are ubiquitous, mold growth in an indoor environment is typically related to water or moisture indoors. Mold growth may also be caused by incomplete drying of flooring materials such as concrete. Flooding, leaky roofs, building maintenance problems, or indoor plumbing problems can lead to mold growth inside. Interior moisture vapor commonly condenses on surfaces cooler than the moisture containing air which enables mold to flourish.   This moisture vapor passes through walls, ceilings and condenses typically in the winter months in climates where the heating cycle is extended. Floors over crawlspaces and basements (without vapor barriers or with dirt floors) are also problem areas. (The "doormat test" is very good at detecting moisture vapor emanating from under concrete slabs that are missing a sub-slab vapor barrier.[6] )

For significant mold growth to occur, there must be a source of water (which could be invisible humidity), a source of food and a substrate capable of sustaining growth. Common building materials, such as plywood, drywall, furring strips,  carpets, and carpet padding are food for molds. In carpet, invisible dust and cellulose are the food sources (see also dust mites). After a single incident of water damage occurs in a building, molds grow inside walls and then become dormant until a subsequent incident of high humidity; this illustrates how mold can appear to be a sudden problem, long after a previous flood or water incident that did not produce such a problem. The right conditions reactivate mold. Studies also show that mycotoxin levels are perceptibly higher in buildings that have once had a water incident (source: CMHC).

Hidden mold

After a major storm or flood one should look out for any signs of hidden mold growth. One can detect mold by the smell and any sign of water damage on the walls or ceiling. Mold can grow in many places that are not visible to the human eye in the indoor environment. Mold is often found behind wallpaper or paneling, the topside of ceiling tiles, back side of dry wall, or the underside of carpets or carpet padding. Piping inside the walls may also be a source of mold growth since pipes often leak and cause moisture and condensation. One must also check in roof materials above ceiling tiles since roofs often leak and water collects inside the walls and insulation. If one is suspicious about mold growth one should investigate with caution to prevent exposure to mold.

Spores need three things to grow into mold:

  • Nutrients: Cellulose is a common food for spores in an indoor environment. It is the part of the cell wall of green plants.
  • Moisture: Moisture is required to begin the decaying process caused by the mold.
  • Time: Mold growth begins between 24 hours and 10 days from the provision of the growing conditions. There is no known way to date mold.

Mold colonies can grow inside building structures. The main problem with the presence of mold in buildings is the inhalation of mycotoxins. Molds may produce an identifiable smell. Growth is fostered by moisture. After a flood or major leak, mycotoxin levels are higher in the building even after it has dried out (source: CMHC).

Food sources for molds in buildings include cellulose-based materials, such as wood, cardboard, and the paper facing on both sides of drywall, and all other kinds of organic matter, such as soap, fabrics, and dust containing skin cells. If a house has mold, the moisture may be from the basement or crawl space, a leaking roof, or a leak in plumbing pipes behind the walls. People residing in a house also contribute moisture through normal breathing and perspiration. Insufficient ventilation can further enable moisture build-up. Visible mold colonies may form where ventilation is poorest, and on perimeter walls, because they are coolest, thus closest to the dew point.

If there are mold problems in a house only during certain times of the year, then it is probably either too air-tight, or too drafty. Mold problems occur in airtight homes more frequently in the warmer months (when humidity reaches high levels inside the house, and moisture is trapped), and occur in drafty homes more frequently in the colder months (when warm air escapes from the living area into unconditioned space, and condenses). If a house is artificially humidified during the winter, this can create conditions favorable to mold. Moving air may prevent mold from growing since it has the same desiccating effect as lowering humidity. Molds grow best in warm temperatures, 77 to 86 °F (25 to 30 °C), though some growth may occur anywhere between 32 and 95 °F (0 and 35 °C).[8]

Removing one of the three requirements for mold reduces or eliminates the new growth of mold. These three requirements are:

  1. Moisture - the key factor. Remove the water, moisture AND humidity and future growth stops.
  2. Food source for the mold spores (dust, dander, etc.)
  3. Warmth (mold generally does not grow in cold environments).

HVAC systems can create all three requirements for significant mold growth. The A/C system creates a difference in temperature that allows/causes condensation to occur. The high rate of dusty air movement through an HVAC system may create ample sources of food for the mold. And finally, since the A/C system is not always running - the ability for warm conditions to exist on a regular basis allows for the final component for active mold growth.

Because the HVAC system circulates air contaminated with mold spores and sometimes toxins, it is vital to prevent any three of the environments required for mold growth. A) Highly effective return air filtration systems are available that eliminate up to 99.9% of dust accumulation (as compared to 5% elimination by typical HVAC air filters). These newer filtration systems usually require modification to existing HVAC systems to allow for the larger size of electrostatic 99.9% filters. However, thorough cleaning of the HVAC system is required before usage of high efficiency filtration systems will help. Once mold is established, the mold growth and dust accumulation must be removed. B) Insulation of supply air ducts helps to reduce or eliminate the condensation that ultimately creates the moisture required for mold growth. This insulation should be placed externally on the air ducts, because internal insulation provides a dust capture and breeding ground for mold.


The first step in an assessment is to determine if mold is present. This is done by visually examining the premises. If mold is growing and visible this helps determine the level of remediation that is necessary. If mold is actively growing and is visibly confirmed, sampling for specific species of mold is unnecessary.

These methods, considered non-intrusive, only detect visible and odor-causing molds. Sometimes more intrusive methods are needed to assess the level of mold contamination. This would include moving furniture, lifting and/or removing carpets, checking behind wallpaper or paneling, checking in ventilation duct work, opening and exposing wall cavities, etc.

Careful detailed visual inspection and recognition of moldy odors should be used to find problems needing correction. Efforts should focus on areas where there are signs of liquid moisture or water vapor (humidity) or where moisture problems are suspected. The investigation goals should be to locate indoor mold growth to determine how to correct the moisture problem and remove contamination safely and effectively.


In general, the EPA does not recommend sampling unless an occupant of the space is sympotomatic. When sampling is necessary it should be performed by a trained professional who has specific experience in designing mold-sampling protocols, sampling methods, and the interpretation of findings. Sampling should only be conducted to answer a pertinent question: examples "what is the spore concentration in the air", or "is a particular species of fungi present in the building." The following additional question should be asked before sampling: "what action can or should a person take upon obtaining data."

Three types of sampling include but are not limited to::

  • Air sampling: the most common form of sampling to assess the level of mold. Sampling of the inside and outdoor air is conducted and the results to the level of mold spores inside the premises and outside are compared. Often, air sampling will provide positive identification of the existence of non-visible mold.
  • Surface samples: sampling the amount of mold spores deposited on indoor surfaces (tape, and dust samples)
  • Bulk samples: the removal of materials from the contaminated area to identify and determine the concentration of mold in the sample.

When sampling is conducted, all three types are recommended by the AIHA, as each sample method alone has specific limitations. For example, air samples will not provide proof of a hidden source of mold. Nor would a tape sample provide the level of contamination in the air.

Though not usually recommended, air sampling following mold remediation is usually the best way to ascertain efficacy of remediation, especially when health concerns of individuals may be at risk, However, the sampling should be properly conducted by a qualified/certified third party following a defined industry standard. [[[Category:All articles with unsourced statements]]


The first step in solving an indoor mold problem is ALWAYS stopping the source of moisture.   Mold will begin to grow on porous surfaces within 24–48 hours. Next is to dry the area without spreading the mold dust and spores while beginning remove the mold growth.

A common remedy for small occurrences of mold would usually include wet cleaning with household cleansers. Care should be taken not to spread or inhale the mold dust and spores.

There are many ways to prevent mold growth; see heating, ventilating, improved insulation and air conditioning.  There are also cleaning companies that specialize in fabric restoration - a process by which mold and mold spores are removed from clothing to eliminate odor and prevent further mold growth and damage to the garments.

Improper methods for cleaning mold include exposure to high heat, dry air, sunlight (particularly UV light), ozone, and application of fungicides.   Both of these last two (ozone and fungicides) are dangerous and if not properly executed, fatal to humans and animals. These methods may render the mold non-viable, however, the mold and its by-products can still elicit negative health effects. As noted in following sections, the only proper way to clean mold is to use detergent solutions that physically remove mold. Many commercially available detergents marketed for mold clean-up also include an anti-fungal agent. However, note that these anti-fungal liquids must be EPA approved, properly labeled, and used in accordance with the stated directions.

Significant mold growth may require professional mold remediation to remove the affected building materials and eradicate the source of excess moisture. In extreme cases of mold growth in buildings, it may be more cost-effective to condemn the building rather than clean the mold to safe levels.  The goal of remediation is to remove or clean contaminated materials in a way that prevents the emission of fungi and dust contaminated with fungi from leaving a work area and entering an occupied or non-abatement area, while protecting the health of workers performing the abatement.

Cleanup and removal methods

The purpose of the clean-up process is to eliminate the mold and fungal growth and to remove contaminated materials. As a general rule, simply killing the mold with a biocide is not enough. The mold must be removed since the chemicals and proteins, which cause a reaction in humans, are still present even in dead mold.

Evaluating mold exposures

Before beginning mold remediation it is important to assess the area infected with mold to ensure safety, clean up the entire moldy area, and properly approach the mold. The EPA provides the following instructions:

  1. Assess the area infected with mold, checking for any hidden mold;
  2. Identify the source of water or moisture that caused the mold growth before you remove and clean up the moldy area to prevent future mold growth issues;
  3. If the area of mold is large you should hire a remediation manager to properly dispose of the mold
  4. Permanently fix the source of the water or moisture;
  5. Check all air ducts, ventilation systems and air handling units so that the mold problems do not persist in the indoor environment
  • Consult a qualified professional if you have any problems or if you are not confident that you can properly remove all mold or sources of mold growth

PRYDE BUILT HOME INSPECTION visually inspects for mold in the readily accessible areas.  However, an in depth physical mold inspection can be arranged if desired by the Client.