MOLD: COMMON QUESTIONS

                                                          What is Mold?

              Mold, together with mushrooms, bracket fungi, and puffballs are classified as fungi. These organisms consist of a mat of hair-like strands called hyphae that form both the main body and fruiting bodies that make spores. Spores are essentially baby fungi with a lunch box. Mushrooms, puffballs, and bracket fungi have large, easily seen fruiting bodies, while molds have tiny fruiting bodies that are visible as a surface discoloration only when there are many of them. Mold coverage ranges from light spotting to thick blooms that cover large areas.
            They can range in color from black to green to white, yellow and red and be present as discrete speckles or large fuzzy masses.
            Mold reproduces by sending microscopic spores sailing on the air or floating on water. Mold spores are typically in the range of 3 to 40 microns in size; for reference, a human hair is typically 100 to 150 microns in diameter. A small colony may release millions of spores.


               When it is above freezing, a sample of outdoor air almost anywhere in the United States is likely to contain hundreds or thousands of mold spores per cubic meter. Consequently, almost all environmental surfaces have spores attached – it is virtually impossible to avoid them.
                In order to sprout and grow into a colony, most spores need to be in a location that provides oxygen, liquid water and/or relative humidity greater than 70%, a source of carbon, and temperatures between 45° F (7.2° C) and 100° F (37.8° C). Once most molds have germinated, they do not need liquid water to continue growing. Unfortunately, these conditions are found in nearly every wallvented crawl space in the southeast for much of the year. Because crawl spaces have numerous air path connections to the house via plumbing penetrations, electrical penetrations, leaky ductwork, and more, we could say that the crawl space is “MADD” – a Mold Amplification and Delivery Device.
Because spores, carbon sources, warmth, and dark spaces are found in all houses, the only realistic strategy for controlling mold growth is to control moisture levels. Eliminating liquid water is the first step.

           Controlling relative humidity is the second step and fortunately, most people are more comfortable at relative humidity levels below the 70% threshold required by most molds.
            Hyphae exude enzymes that may decompose organic materials so the nutrient can be absorbed into the hyphal mat. That, in fact, is their ecological job – to decompose dead plants and animals. Molds are essential to the proper workings of the natural world. Most molds are not good at digesting cellulose. Wood decaying fungi (soft rot, white rot, or brown rot) are the organisms that actually decompose solid wood, and they generally require very wet wood with a moisture content of 30% or more. Soft rot requires the continual presence of liquid water.
             Brown rot usually occurs on wood in contact with damp soil or a continuous water source, but can also be caused by molds that transport moisture from some other location (this latter type is typically referred to as “dry rot”).

            Crawl spaces with long-term condensation, standing water, or exposed soil are vulnerable to any of these molds, especially at lowtemperatures caused by air conditioning below 72° F (23° C) or in colder climates with low soil temperatures. Sap stain or blue stain fungi may cause discoloration of cut lumber but are notreported to lead to rot or structural damage and probably do not present an air qualityconcern. Sap stain fungi can be mistaken for Stachybotrys species due to their darkcoloration, but scientists note that the growth of Stachybotrys species on wood is extremely poor and rarely occurs. Stachybotrys species (e.g. S. atra or S. chartarum) typically occur on fiberboard, gypsum board, paper, dust or lint.

             These molds are associated with constant high levels of moisture resulting from flooding, unrepaired plumbing leaks or standing water. They are not often found in crawl spaces.
Growth of other fungi on solid wood in drier conditions (19-30% wood moisture content or ambient relative humidity above 70%) is generally limited to the surface and does not cause structural damage.

            Composite materials like engineered wood products consisting of bits of wood and adhesives can be structurally degraded by molds because the mold can often digest the adhesives. Composite materials must be dried and cleaned very quickly to prevent damage.

                            Should I Test for Mold?

             Mold testing is not recommended usually unless there is a specific need to identify samples by species. As detailed below, it is generally expensive and time-consuming
to get reliable mold sampling and analysis. Visible mold, regardless of species, indicates a moisture problem that requires attention. In some cases, molds are located in hidden areas or are simply not visible to the naked eye.
Whether visible or not, the key to suppressing mold growth is to remove the mold’s moisture source. The generally accepted practice for bioaerosol sampling, as laid out by the American Conference of Governmental Industrial Hygienists (ACGIH), is to compare indoor samples with outdoor samples taken at the same time. If the spore concentrations are significantly higher indoors than outdoors or the species mix is significantly different indoors than outdoors, it is evidence that mold is growing inside the building. Unfortunately, interpreting the results of bioaerosol sampling is fraught with sources of uncertainty:
• In sample sets taken at a few locations over an interval of hours or days, false positives and false negatives are common. To reduce the chances that something important has been missed, numerous samples must be made over extended time periods.
• Bioaerosol sampling requires trained technicians with specialized equipment, and
even then, measurements vary significantly over short time frames.
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        Ideally, mold samples should be “speciated,” or counted and categorized by individual species of mold present in the sample. Speciation provides better evidence for distinguishing whether there is independent mold growth in a building (or part of the building) or whether the mold in the building simply reflects the mold present in the surroundings.

          “Viable” spore counts are easier to speciate than total spore counts, but viable spore samplers may be biased towards smaller species, and growth conditions can vary depending on the lab doing the analysis. Tape lifts and direct microscopic examination of surfaces are other techniques to identify the presence of mold and, to some extent, identify the mold. These techniques also require trained specialists and do not generally allow for speciations.
         Finally, even if sampling is detailed and comprehensive enough to provide confidence in the measured results, there is no consensus on numerical standards to which test results
can be compared to indicate a dangerous condition. Human reaction to mold varies greatly from individual to individual.

                      Should I Clean Up Existing Mold in My Crawl Space?

          Mold does not necessarily have to be cleaned up as part of a strategy to improve a crawl space. Molds go dormant as their environment dries out. However, dormant mold can still trigger allergies, asthma events, or other symptoms in susceptible individuals. Potential health impacts and the reporting of mold by private home inspectors prior to home purchases is causing more and more homeowners to consider removing or “remediating” mold from their crawl space.

           The homeowner’s choice of whether or not to clean up mold depends on their level of concern about the potential health impacts of leaving the mold in place or the impact on the value of their home. One specific benefit is that cleaning out existing mold will make it easier to detect a recurrence in the future. Of course, there is no point in cleaning up surface mold without improving the moisture conditions that allowed the mold to grow in the first place. The mold would simply grow back.

            Any activity to clean up surface mold should be part of an overall plan to close the crawl space permanently.
Mold-contaminated ductwork also presents the question of whether to leave the mold in place, clean the ductwork, or replace the ductwork. Flexible duct and fiberglass-lined ductwork is very difficult, if not impossible, to thoroughly clean. Other options include leaving the duct as is, replacing the ductwork or spraying fungicides or encapsulating materials to isolate the mold in the duct from the air stream. Sheet metal ductwork is generally more feasible to clean and reuse without encapsulation.
             Some experts recommend that you seal ductwork and seal holes between the house and the crawl space whether or not the mold is cleaned up. This air-sealing work reduces the chance that mold, mold byproducts or other contaminants in the crawl space can enter the living area of the home by air transport. It is also critical to help prevent new or cleaned ducts from becoming recontaminated. For additional protection, the homeowner can upgrade air filtration in the house with standalone HEPA units or HEPA air handler/duct system filters, and/or apply a fungicide over the existing mold to provide short-term antifungal activity and some level of continued suppression.
            There have been several reports of strong ammonia-like odors associated with the drying-out of existing crawl spaces in the southeast , which may be the result of the mold slowly dying or going dormant. The odors persisted for weeks or months without dissipating. Application of a fungicide in conjunction with reducing moisture levels has been reported to eliminate or prevent this problem.

If a property owner does decide to clean up existing mold, work can range from spot cleaning of affected areas to comprehensive cleaning of most, if not all surfaces. Large jobs are likely too labor-intensive and time consuming to do as a home project. In these cases, property owners can contract for professional cleanup services from water damage or mold remediation companies.
Building performance or other contractors may also offer this service.

      This guide is by no means a complete reference for doing safe and effective mold remediation, but simple advice is provided below.
        During any cleanup, it is recommended the following steps to help reduce the chance of cleaning materials, mold toxins, mold spores, mold fragments, or other contaminants moving from the crawl space to the living space:
• Turn off any heating and cooling system that utilizes ductwork in the crawl space.
• Reduce or stop the use of exhaust fans and clothes dryers in the living space.
• Pressurize the living area with HEPA-filtered air and/or depressurize the crawl space.
Additional notes on cleaning mold:
• Remove as much contaminated material as possible before beginning cleanup.
• Remove contaminated or damaged insulation. Porous insulation that has been wetted should be replaced, since it will likely never recover its designed R-value, even
when thoroughly dried.
• Not all fungicides are effective on all materials. Follow all manufacturers’
recommendations for application and safe handling. Swimming goggles can provide
eye protection when working overhead.

• Chlorine bleach is not a long-term fungicide. If you use chlorine bleach, never mix it with ammonia because toxic gas can be produced in fatal levels.
• Liquid cleaning or dry scraping may not remove all staining caused by surface molds.
• HEPA vacuums can be used to collect surface mold removed by scraping, and are recommended instead of sweeping to clean up debris on surfaces or the crawl space floor.
• Pressure washing, sanding or blasting with baking soda or dry ice are cleaning options that may remove staining. Residual materials should be removed afterwards.
• Application of sealants, primers, and paint topcoats may be required to completely
cover stains and resist bleed-through.
• Replace the ground vapor retarder after a cleanup operation.
• Air-sealing and subfloor repairs are easier while insulation is removed.
• Fungicides can be applied after cleaning to encapsulate mold spores that were not
removed and to provide some level of continued mold suppression.
• Monitor and control relative humidity below 70% after cleanup to reduce the risk of mold growth recurring.

                                           Does Mold Make People Sick?

              At the time of this writing, the scientific and medical research communities have not documented a causal relationship between mold growth in residences and human illness.
               There is an association between damp home environments and occupant medical conditions like allergic rhinitis and asthma, however it is unclear whether mold or some other substance or organism (for example, bacteria) that exists in the same conditions is responsible for the symptoms.
                 The bottom line is that it is clearly less healthy for humans to live in homes with moisture problems, and strategies that eliminate the potential for such problems are beneficial.

                 Health effects generally attributed to mold exposure are of four types: allergy, irritation, infection, and toxicity.

The most commonm health effects are allergic reactions and asthma events. The symptoms can include runny nose, eye irritation, sinusitis, and difficulty breathing.
A tiny fraction of allergy sufferers may develop more serious, chronic lung disease from chronic exposures. Most molds release alcohols and sulfur compounds, which can irritate mucous membranes and the trigeminal nerve ending in the back of the throat, which reacts to pungency and irritation. People are sometimes infected by molds, but generally, people become colonized by molds only if their immune system is not functioning well.
Some molds produce toxins called mycotoxins. Mycotoxins are not produced as part of the act of living, as are the compounds from respiration and nutrient decomposition.
         They are produced only occasionally by some mold species. It is thought that molds are most likely to produce toxins when in competition with other molds or bacteria for habitat. In this case, people are collateral damage in chemical warfare between microscopic creatures. The best-documented cases of mycotoxin poisoning are from veterinary medicine when livestock eat mold-contaminated material. There is not much human data to help us understand the risks from mycotoxin exposure, however, the toxins do exist and some of them are similar in toxicity to nerve gases.

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                            What Can You Do?

In the kitchen and bathroom, open windows or use exhaust fans when engaging in activities that produce moisture. Exhaust fans should be vented to the outdoors and not to an attic or crawl space.

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A word of caution:

         Building inspectors, contractors, consumers and the do-it-yourself group should always exercise caution when working with radon, formaldehyde, carbon monoxide , mold, insulation,  lead based paints or other potential health hazards. Through training and education informed choices are made. Don’t get in over you head! It is O.K.  to seek professional help if you are not certain.

 A Final Note:

Carbon Monoxide Detectors and Smoke Alarms save lives. We as building inspectors, contractors and consumers have known this for years. But we must remain diligent in or training and education efforts.