I have a question about sanding, specifically drywall. I know that the S520 standard does not recommend this practice, but I am preparing to assist on a job where another remediator has suggested it. Specifically he suggested "vacuum sanding the...
Q.) I have a question about sanding, specifically drywall. I know that the S520 standard does not recommend this practice, but I am preparing to assist on a job where another remediator has suggested it. Specifically he suggested "vacuum sanding the drywall" because there is no visible mold on the backside. Have you ever heard of this being done? Would vacuum sanding be good for small spots?
A.) You are correct that the S520 does not recommend sanding drywall. I can only assume that the drywall is a painted surface and not covered with wallpaper. The removal of the wallpaper and sanding of the drywall would probably be more time consuming and costly than removing the drywall. With that in mind, let's first of all exam how drywall gets wet. There are a number of ways that drywall can get wet enough to support mold growth. Some examples include:
- water that flows along the floor;
- water that comes from above;
- water that moves through a concrete slab that results in wet drywall;
- moisture or vapor that moves through the building envelope from the outside to the inside; or
- moisture or vapor that moves through the building envelope from the inside to the outside.
Water that flows across a floor or water that comes from above can result in walls that come into direct contact with the water. When water flows across a floor, it can also be drawn into the drywall by capillary action. In these cases both sides of the drywall will probably be wet. The interior of the wall cavity will most likely remain wet longer that the side of the drywall that faces the living area. This is probably not the scenario that caused the problem that you are describing. The reason is that it is more likely to have mold growth on the interior of the wall cavity.
The third example will most probably result in both sides of the drywall becoming wet. The same results exist here as with the previous example. In this case, there is a greater probability of mold problems since the walls are likely to be wet longer than in the first example. Again this is not the scenario that caused the problem that you are describing.
The fourth and fifth examples are more likely to have caused a condition where there can be mold growth on the side of the drywall that faces the living area only. When moisture moves through the building envelope from the outside to the inside, it is possible for mold to grow wherever the moisture vapor comes into contact with a surface that is cold enough to result in condensation. That surface could be inside the wall cavity or in some circumstances the water vapor will move through the interior drywall and condense on vinyl wallpaper. In other instances, the moisture can move through the drywall and possibly condense on other surfaces adjacent to the wall. For example, we were asked to investigate a mold problem in a school after the janitors had moved file cabinets away from an exterior wall for summer cleaning and maintenance. Once the cabinets had been moved, mold was discovered on the painted drywall. The school was located in California where the outdoor climate was hot and dry; the inside of the school was air-conditioned. In order to maintain the grounds, the lawn was regularly watered. The sprinklers were directed at the exterior of the wall where mold had been discovered. It was believed that moisture had moved from the hot exterior to the cooler interior resulting in mold growth on the drywall. It was determined that there was no mold growth on the interior of the wall cavity. The water, in the form of a vapor, had moved through the exterior cladding, through the wall cavity, then through the drywall and condensed on the back of the metal file cabinets. The file cabinets were close enough to the wall to result in the drywall becoming wet. There was mold growth on the side of the drywall that faced the living area only. Another way that this same pattern of growth could develop is if the indoor relative humidity condensed on the drywall and resulted in mold growth only on the side of the drywall that faced the living area.
When there is mold growth on the surface of painted drywall, S520 makes the following recommendation:
Small isolated areas of mold growth on a surface layer of condensation on enamel-painted walls or other non-porous surfaces, and mold growth has not resulted in concealed areas, usually can be removed by HEPA vacuuming and damp wiping as part of a regular maintenance program.
This is a restatement of what was recommended by the American Conference of Governmental Industrial Hygienists (ACGIH) in their publication Bioaerosols: Assessment and Control. ACGIH makes the following suggestion and comment:
15.2 Removing Existing Contamination
Growth that has occurred in a surface layer of condensation on painted walls or non porous surfaces (including wood) can usually be removed by (a) vacuuming using equipment with high efficiency filters or direct air exhaust to the outdoors, (b) washing with a dilute solution of biocide and detergent, or (c) cleaning, thorough drying, and repainting. Porous materials that have sustained extensive microbial growth must often be removed. Examples of porous materials are ceiling tiles, installed carpeting, upholstered furnishings, and wallboard. Extensive microbial growth refers not only to the extent of the area affected but also the degree to which microorganisms have degraded a material for use as a food source.
The latter document recommends either cleaning the surface or replacing the material. S520 follows the same line of thought. What purpose would be served by sanding drywall? If the growth is so extensive that it requires sanding, then I would suggest that is fits ACGIH’s description of a material that has been degraded sufficiently to warrant replacement. It seems to me that sanding of drywall would be more time consuming and costly than cleaning. Additionally, there might be more cost to prep the surface for repainting. Finally, I would think that HEPA vacuuming the surface, then cleaning would be less likely to cause an aerosolization of mold spores. That means that there would less risk of contaminating the surrounding area and less risk of litigation.
— Jim Holland
I’ve heard conflicting comments about misting to reduce dust in the air during mold remediation. My question is whether or not misting is appropriate?
The use of misting during mold remediation is controversial. On one hand misting can reduce suspended dust in the air and on the other hand there is evidence that misting may cause the dispersal of mold spores.
Dust is a general term that refers to minute solid particles that are finely divided or separated. They are generally less than 500 microns is size and can be comprised of a wide variety of substances. Ohio State University describes house dust as being generated from several sources including but not limited to:
- The breakdown and release of plant and animal materials used in the home. These contaminants include such items as feathers, cotton, wool, jute, hemp, and animal hairs. They come from clothing, carpets, rugs and furniture.
- The disintegrated stuffing material from mattresses, pillows, quilts, and upholstered furniture. Prolonged use seems to cause these resilient fibers to weaken and eventually break down into particles small enough to be inhaled.
- Human skin scales, animal dander, insect parts from cockroaches and dust mites, saliva, molds and mildew, bacteria, viruses, and pollen. As people go through their daily activities, particles that have settled onto the floor and other surfaces are stirred into the air.
- Other contaminants deliberately introduced into the indoor environment. These can include tobacco smoke from pipes, cigars and cigarettes, cosmetic powders, baby powder and some powdered laundry detergents, aerosols such as air fresheners, and cleaning products with strong odors. During mold remediation it can be expected that mold spores, fungal fragments and abraded building materials will be added to what ever mixture might already exist.
Some of the components of dust are hydrophilic (water loving) and other may be hydrophobic (water fearing or hating). The practice of using a mist of water to remove hydrophilic dust from the air has been used for centuries. Most recently misting has been used to assist in removing asbestos particles form the air during abatement. Asbestos is hydrophilic and when water, in the form of mist, comes into contact with minute asbestos particle, they tend to combine. The combined weight of the asbestos and the water causes the particles to fall out of the air space. A similar process can be used in lead abatement when dust is created from abrading surfaces that potentially contain fragments of lead. Misting has also been used to control dust that is generated by stirring up dirt and the particles of gypsum board dust that are created during demolition.
However, it has also been reported that hydrophobic particles in the atmosphere are not necessarily removed by the formation of water droplets. Fan, S. et al, stated in their article entitled “Impact of air pollution on deposition of mineral dust: Implications for ocean productivity” that “African dust over the tropical Atlantic is mostly hydrophobic and removed by ice, but not droplet, nucleation.” The authors of a report entitled Thunderstorm asthma - mold spores causing huge increases suggested that asthma may have been caused by an increased release of fungal spores due to an initial rainfall. The study indicated that there was a reduction of certain airborne particulates and an increase of mold spores. The fact that many spores are hydrophobic can account for the increase. Professor of Botany George Wong from the University of Hawaii makes the following reference to aerosolized dry spores:
These spores do not readily soak up water and when clusters of these spores are splattered by water, as may often occur in those fungi that produce their spores directly on their mycelium, rather than absorbing the water, the impact dislodges the spores and scatters them into the wind. Because these spores do not readily absorb water, they are said to be hydrophobic. Although this may not be very intuitive, the initial resistance of these spores to water makes a great deal of sense.
If controlled demolition is employed, as described in the IICRC S520 Standard and Reference Guide for Professional Mold Remediation, dust generation can be minimized. Using HEPA filtered negative air machines to capture any released particulates also minimizes the need to control dust by using a water mist as a control measure. On the other hand if misting is used it adds a moisture source that needs to be controlled. If the use of misting results in workers being less diligent about controlled demolition, then more dust will be generated and more misting will be employed. The more moisture used the greater the likelihood of increased labor and costs. There is also the potential for too much moisture being added to the environment requiring dehumidification or causing secondary damage to building materials. We have seen cases where uncontrolled moisture from misting has resulted in additional mold that wasn't present before the remediation began. I’m not suggesting that there are not occasions where misting might be appropriate. Certainly there might be situations where the contractor has no choice. For example a mold remediation performed on asbestos containing materials. The asbestos construction standard requires that misting be used to control the asbestos particles. Of course asbestos abatement requires special training and licensing and should never be performed by any firm that is not in compliance.
Even if containment and negative air are used, there is a risk to workers. In one situation, monitored by our company, an asbestos abatement company performing mold remediation on asbestos containing materials utilized misting with water during the demolition. Air sampling during the demolition demonstrated 27,000,000 cfu/msup>3 (colony forming unit per cubic meter) of culturable water damage related mold spores in the air within the work area. The crew members were wearing full face air-purifying respirators with HEPA cartridges, but even with that level of respiratory protection, the effective exposure that might be expected due to leakage around the face piece could be 540,000 cfu/m3. This represents a much higher concentration than we have ever measured during controlled demolition without the use of misting. Fortunately containment and negative air were being used which prevented the spread of contaminants to other parts of the building, but worker exposure was still an issue.
Remediators choosing to use misting should be prepared to monitor the contained environment. Thermo-hygrometers and moisture meters can be used to monitor humidity and moisture levels respectively. If moisture levels begin to increase, dehumidifiers might be needed to maintain acceptable conditions. Particle counters can be used to check for higher than normal levels of particulates in the air. In some circumstances the involvement of an indoor environmental professional may be appropriate to assess the work environment during remediation and misting operation. If extremely high levels of mold spores develop, the use of powered air-purify respirators (PAPRs) might be necessary.
— Jim Holland
What is a "normal fungal ecology"?
"Normal fungal ecology" is a term that was arrived at by consensus while developing the First Edition of the IICRC S520 Standard and Reference Guide for Professional Mold Remediation (S520). It was intended to describe an indoor environment that was not contaminated.
The S520 defines these 3 conditions:
Condition 1 (normal fungal ecology): an indoor environment that may have settled spores, fungal fragments or traces of actual growth whose identity, location, and quantity is reflective of a normal fungal ecology for a similar indoor environment.
Condition 2 (settled spores): an indoor environment which is primarily contaminated with settled spores that were dispersed directly or indirectly from a Condition 3 area, and which may have traces of actual growth.
Condition 3 (actual growth): an indoor environment contaminated with the presence of actual mold growth and associated spores. Actual growth includes growth that is active or dormant, visible or hidden.
contaminated (contamination): the presence of indoor mold growth and/or mold spores, whose identity, location and quantity are not reflective of a normal fungal ecology for similar indoor environments, and which may produce adverse health effects, cause damage to materials and/or adversely affect the operation or function of building systems.
You might note that Conditions 2 and 3 are "contaminated" and that Condition 1 lacks the same term in its description. All three terms should be understood in light of their being or not being contaminated.
Writing a standard has many unanticipated problems. When discussing an uncontaminated or clean environment, there was concern about what "clean" meant. "Clean" does not always mean the same thing to everyone. To some "clean" means that its appearance is acceptable and it does not have an odor, but does that mean that it is uncontaminated? The answer is: not necessarily. After cleaning, it might be assumed to be clean. The only way to determine whether it is uncontaminated is to test or sample the surface. There was some concern that the S520 would overstate what "clean" meant. In other words, it could be interpreted as meaning that the surface was free of molds or mold spores. Such a conclusion would lead to excessive remediation efforts and unnecessary additional costs. Since molds are ubiquitous, it was recognized that any environment was going to have some molds or mold spores present, which does not rise to a level of "contamination."
The S520 Consensus Body was attempting to carefully and accurately describe an uncontaminated indoor environment recognizing that such an environment has variability with respect to the types and quantity of molds present depending upon its unique circumstances. Therefore, a Condition1 area may have settled spores, fungal fragments or traces of actual growth that is not reflective of a contaminated environment.
There has been criticism over the term "normal fungal ecology" because it does not clearly state what a "normal fungal ecology" is in terms of what kinds or quantities of molds or mold spores would be present. The Consensus Body never intended to quantify or definitively define what a "normal fungal ecology" is or was. The Consensus Body recognized the need for an indoor environmental professional to assist in making that determination. Notice what is stated in the S520 Preface:
S520 is not intended to establish procedures or criteria for assessing mold contamination in an indoor environment. These issues are most appropriately addressed by professional organizations that represent Indoor Environmental Professionals (IEPs). Since these professional organizations have not agreed upon threshold exposure limits or levels of visible mold growth that constitute a concern for occupant and worker safety, the IICRC Mold Remediation Standard Committee decided not to establish action levels or procedures based upon the quantity or size of the area of visible mold growth.
This statement was also printed in the Standard in bold type to draw the reader's attention to the statement. The same problem exists with the term "normal background levels." What is that? Each environment is unique and therefore an appropriate sampling strategy by an IEP is needed to determine what the normal or acceptable fungal condition for that specific environment (a "normal fungal environment" or "normal background levels") happens to be. Also, there has been a criticism over the use of the term "ecology" since it could refer to the molds' surrounding environment instead of an occupants' surrounding environment. The interpretation depends entirely on a persons' perspective. In this context it refers to our surrounding environment where we live, work and exist.
The English language is sometimes very difficult to master. Words and phrases can mean different things depending upon their context. The environmental community uses terms that are likewise hard to understand, such as viable or non-viable sampler. A non-viable sampler does not collect only non-viable spores or particles nor is the term "non-viable" meant to be interpreted as meaning that this type of sampler is not practical or not workable, as the term is sometimes defined. In reality, the term non-viable sampler means that the sampler is not used to collect spores for the purpose of culturing them. It means nothing more and nothing less. The S520 Consensus Body met and discussed these terms many times over a couple of years. There were participants from various industries that helped to develop the language. At one particular meeting a number of participants were asked to form a separate Ad hoc committee that met independently. They were instructed to create language that best described a remediated or uncontaminated building, system and contents. As I recall, the committee included several PhDs (Chemical Engineering; Public Health; and Microbiology), a CAIH, a California EPA Registered Environmental Assessor, an environmental consultant and two remediators. The language changed many times in an attempt to be clear. However, the language needs to be considered in light of the entire document, not out of context. Because of the variability in each environment there cannot be a black and white statement that defines a "normal fungal ecology."
Recently, a member of the IEQuality Yahoo discussion group made the following comment:
"It's practically impossible to clearly define what is considered to be 'normal' on a specific building material in [a] certain type of building at its own age located in each climate regions."
The comment is absolutely correct. This is the very reason why the committee did not further define the term or the condition. The committee knew, or at least hoped that when it decided to use the term "normal fungal ecology," it would move the IEP community to address the issue.
In a recent article entitled The 2006 Winter Solstice and the Future of IAQ, Dr. Bob Brandys, President of Occupational and Environmental Health Consulting Services Inc., stated that:
"The creation of the concept of 'normal fungal ecology' was a brilliant first step in acknowledging that mold spore levels in the indoor environment are never zero. But what exactly is 'normal fungal ecology' in buildings? We could surely use a better scientific delineation of this concept."
Dr. Brandys' approach was to try to understand what the S520 Committee was attempting to say and then to seek a solution. I personally hope that the indoor environmental quality (IEQ) industry does help to establish a "better scientific delineation of this concept." That is where the definition of what a "normal fungal ecology" should come from.
The viewpoints presented in this article are my personal opinions and not an official position of the IICRC, the IICRC S520 Consensus Body, the S520 Edit Committee, or the IICRC Standard Committee.
— Jim Holland