Frequently Asked Questions:
Furthermore, some types of mold grow much faster (e.g., Cladosporium) than other types (e.g., toxic mold or Stachybotrys). The faster growers may overtake the culture media and/ or prevent the growth of the more important slow growers. So, when you use a culture based method, you can miss important mold types.
With the culture based method, the spores must be alive to reproduce and be detected. With the MOLDetect® test kit you are able to detect both the viable (living) and non-viable (dead) spores, and both living and dead spores mold spores continue to be allergenic and toxigenic even if they are no longer alive (e.g., after being treated with a disinfectant). Therefore, the tape lift surface sample method or MOLDetect® kit enables all spores in the sample to be detected. Also, most culture based kits have an additional charge for lab analysis if you want to identify the mold types present. This can cost an additional $30-$50 plus postage above the cost spent on the original purchase. It usually takes up to an additional week for an analysis result.
It is important to understand that there are always some mold spores present indoors, since they naturally infiltrate inside from their origin outside. Thus, if a culture plate is opened up inside to take a sample, you will ALWAYS GET GROWTH OF MOLD. The growth on a plate will probably look fuzzy and perhaps even fill up the plate, which can be alarming to the person testing, even if there are only one or two normal outdoor type spores present (which is a normal situation). The growth of fuzzy or any other type of mold does not tell you there is an abnormal situation or problem. You would send the plate to the lab to learn what molds are present and if they represent an abnormal situation.
Experts from the ACGIH (American Conference of Governmental Industrial Hygienists) say that settle culture plates do not collect airborne particles in a way that allows you to properly evaluate conditions. “Particle settlement depends on the size (weight) of the particle size and also is influenced by air movement. Therefore, settle plates do not provide reliable measurements. This method is not even appropriate for determining the relative air concentrations of different microorganisms because of the collection bias.”
“Fungal growth in buildings is undesirable and may cause health problems for building occupants…..indoor fungal growth is inappropriate and should be removed.” [ACGIH Bioaerosols Assessment and Control 7.4.2].
Indoor Air Quality and Mold
Frequently Asked Questions:
The word mildew actually describes specific types of outdoor molds that are pathogenic to plants. There are two kinds of mildew, ‘powdery mildew’ and ‘downy mildew’ that infect plants. For more information, please see: mildew information
There has been a lot of litigation in recent years related to mold exposures inside buildings. If a building has a mold problem, there may be media coverage of the issue or related bad publicity.
Additionally, mold can cause property damage because it consumes (destroys) what it is growing on.
Indoor mold growth is inappropriate and should be addressed. The basic rule is, if you can see or smell mold, take steps to eliminate the excess moisture, and to cleanup and remove the mold.1
Irritation: Exposure to mold can irritate the eyes, nose, and upper breathing passages. Symptoms of irritation include burning eyes, nasal congestion, coughing, and post-nasal drip.
Allergy: Many people become allergic to mold and develop hay fever or asthma symptoms such as itchy, watery eyes, nasal congestion, sneezing, chest tightness, cough and wheezing.
Toxins: Some molds create chemicals, called toxins that can cause illness. While much remains unknown about mold toxins, it appears that some produce toxins that can have effects on the skin, the respiratory system, the immune system, and the nervous system.
Infection: Some molds can also cause infection, such as chronic sinus infections. Other types of mold-induced infection are much less common, and occur mainly among people with weakened immune systems. Examples of individuals with weakened immune systems include those with HIV infection, those receiving chemotherapy, and the elderly. Children and pregnant women may also be at increased risk.2
Indoor air quality affects the health and comfort of occupants. Good indoor air quality can have a positive effect on productivity, health morale, quality of life. Good indoor air quality can prevent lost workdays due to illness, help avoid costly litigation and maintain property values.
The same is true for a crawl space. If the ventilation system (furnace and/or ducts) is located there, it can pull contaminants into the system and they will be distributed in the interior of the house.
Thus it is always important to keep the area around the furnace and ducts mold free.
- Mold spores
- Any organic food source, living or dead (carbon based)
- Appropriate temperatures (normal human living temperatures); and
- Moisture (water)
** Mold spores are ubiquitous (present everywhere); ** Dust is a good carbon food source; ** Fungi require the same temperatures that humans require.
The only growth requirement that can be controlled to prevent mold growth is MOISTURE. Therefore, it is important to maintain the indoor relative humidity below 60% and address water leaks, spills, or flooding as soon as possible. Building materials that remain wet for more than 24-48 hours can grow mold.
A mold that is capable of producing mycotoxins does not also produce them. Whether or not a mold produces mycotoxins while growing on a building material depends on the substrate, conditions such as temperature, pH, humidity or other many other undetermined factors.
When mycotoxins are present, they are in the living spores, but also remain on the membranes of dead mold spores. Therefore, the hazard is not eliminated by killing the spores with Clorox or other anti-fungal agent. To actually eliminate the hazard, you must physically remove the spores. If the mold is growing on a porous material, the toxins may also be present in materials they are growing on.1
MOLDetect® tape lift samples taken from dust deposited on the outside (or inside) of a supply/ return air register or from the furnace filter can be helpful in determining if the ventilation system has been contaminated with abnormal levels or types of spores from indoor mold amplification (growth). A sample with a visible deposit of dust is required for proper analysis.
If you know or suspect that the ventilation system is contaminated, refrain from operating the heater or air conditioner if at all possible until the system has been cleaned. Cleaning should be done by a NADCA certified duct cleaning service and be comprehensive, including the furnace fan, ducts, registers, a/c coil and attached humidifier.
- 1. California Department of Health Services: “Mold in My Home: What Do I Do?”
- 2. July 2001 EPA Mold Remediation in Schools and Commercial Buildings,
- 3. The Facts about Mold: April 2001 NY Committee for Occupational Safety and Health