By Bruce Bowen
Visible mold growing inside your home or business may pose serious health risks for some people, and it should be properly removed as soon as possible.
Mold spores, which are similar to the seeds of a plant, are microscopic in size and ever-present in the air and on surfaces, both inside and outside of buildings. There are several stipulations necessary for mold spores to take root and grow, and it must have a growth medium, excessive moisture, and time to grow. A bit of dust, or soil, or food residue on any surface (even concrete or tile) is enough to serve as a growth medium for mold or other microbes. Porous materials such as carpet or drywall can be an excellent growth medium. Humid conditions combined with warmer temperatures can accelerate the growth of some types of mold. When moisture remains in a suitable growth medium for more than a day or so, mold and other microbial growth is possible and likely, which is why it is important to keep an indoor environment clean and dry.
Once mold becomes visible to the naked eye, it is usually active and growing. “Black Mold” is a common expression utilized when visible growth is identified. When this occurs in an indoor environment, it may be cause for concern, and you should contact a mold remediation professional to perform a visual inspection to attempt to identify any potential excessive moisture issues. The restoration technician will begin by checking for wet conditions in the building. Moisture plays a critical role in fostering the growth of microbes, so the amount of moisture present in the air, the building contents, and the building materials must all be taken into consideration. The technician will attempt to determine the source of any excess moisture. Any leaks or other sources of excess moisture must be addressed.
The technician may employ any of several methods and devices to measure the moisture in each of the areas above. The tool used most commonly by professionals for measuring moisture in the air is a thermo-hygrometer (sometimes called a psychrometer), which is essentially an electronic psychrometric calculator. The primary readings used by the technician are temperature and relative humidity. The readings from the psychrometer may also be inserted into a psychrometric chart. From this, the technician can see the relationship between relative humidity, temperature, dew point, and the humidity ratio. Relative humidity is the percentage of moisture in the air compared against the quantity of moisture the air is capable of holding at a given temperature. Dew point is the temperature at which water will begin to condense from the air onto surfaces. The humidity ratio is the actual amount of water vapor in one pound of dry air, usually expressed as a ratio of grains of water vapor per pound of air (GPP).
There are several tools used to determine the moisture content of the materials in the building. A non-penetrating moisture meter will measure to a depth of approximately 3/4 of an inch. Most have separate settings for wood, drywall, or masonry. Wood moisture content is measured as a percentage, while other materials use a points scale. A pin-type penetrating moisture meter is employed to check for moisture deeper than 3/4 inch, or to check for wet materials behind a wall or under a floor. It has probes that must be driven into or even completely through one material to test for moisture in another, such as insulation or studs behind drywall, or subfloor materials beneath a vinyl rug. Another method for finding wet materials that may not be visible to the naked eye is with an infrared camera. Infrared cameras are extremely sensitive, with the ability to detect temperature differences to as little as .05 degree Fahrenheit. They can enable the technician to locate wetness in buildings that cannot be found using conventional moisture meters.
The moisture levels in most materials must be measured against a ‘dry standard’, which will vary with local environmental conditions. The dry standard for materials in a building along the Gulf of Mexico will usually allow for a higher average moisture content than for materials found in a building in the Desert Southwest for example. The technician will take readings from an area of the structure, or a neighboring structure, that has not been affected by the water damage event to set a ‘drying goal’ for each type of material, which will approximate the dry standard.
When a building incurs a water loss, the level of wetness is classified, and the level of contamination is categorized according to standards established in the S500, a manual by the Institute of Inspection Cleaning and Restoration Certification (IICRC). Water damages are divided into 4 Classes.
• Class 1 water damage is the least amount of wetness, confined mainly to the floor with only part of a room or area affected and little or no wet carpet or carpet pad.
• Class 2 is a significant amount of water, with very wet flooring materials in at least an entire room and moisture wicking up the walls no more than 24 inches.
• A Class 3 water loss is the greatest amount of water, with entire rooms saturated from ceiling to floor, where water may have leaked down from above.
• Class 4 is a Specialty Drying situation, with hard to dry materials such as concrete, plaster or masonry, and deep pockets of saturation, which may require very low humidity or heat to dry.
Water contamination is broken into three categories:
• Category 1 water is water from a clean or sanitary source, which may be from a broken supply line, or toilet tank or bowl. Category 1 water can degrade over time to Category 2 or 3 with exposure to higher temperatures or contaminants, such as animal feces or animal carcasses.
• Category 2 water is mildly contaminated, and may cause illness or discomfort if ingested. Sources of Category 2 water may include a washing machine or dishwasher overflow, toilet overflow with no feces or a small amount of urine. Category 2 water can degrade to Category 3.
• Category 3 is grossly contaminated water which would likely cause serious illness or death if ingested. Examples include sewage, intruding water from flooding rivers or streams, toilet back-ups that include feces, or water that has been sitting long enough to support microbial growth. Water associated with a significant mold loss is usually considered to be Category 3.
If mold is discovered or suspected, the restoration company will usually contact a third party Certified Industrial Hygienists to take samples and have them tested. Samples are normally taken from surfaces inside the building, and from the air both outside and inside of the building. The process of taking samples may require somewhat intrusive measures, such as moving furniture, lifting carpeting, opening air condition ducting, or even removing sections of drywall or flooring. The hygienist will take the samples to a laboratory to be examined under a microscope to identify the type and quantity of any microbes present. The results for the interior and exterior samples are compared against each other. The quantity of mold spore for a given volume of air should be somewhat less indoors than outside. The type and amount of microbes normally present in the local environment are also taken into consideration. It is not uncommon in cases of severe interior mold infestations that the quantity of mold spores discovered in the interior air samples is significantly higher than the outdoor sample. Another indicator of an interior mold problem is the presence of a significant quantity of spores from the indoor air sample that is of a different type than the majority of spores present in the outdoor air sample.
When the results of the laboratory analysis are positive for mold, a remediation protocol is developed. This protocol must be followed by the mold remediation professional. Before the remediation can begin, any standing water must be removed from the environment. Air scrubbers (Air Filtration Devices or AFD) may also be installed inside the building. Air scrubbers are high-efficiency particulate arresting (HEPA) air filters, which remove 99.97% of particles from the air, down to a size of .03 microns. This filtration level is fine enough to capture the majority of mold spores, which can help reduce the amount of it in the air, and the likelihood that the mold will spread.
Technicians must don the proper personal protective equipment (PPE) before beginning the remediation. Different levels of PPE may be required depending on the project. This usually includes an impermeable suit and gloves, a respirator and eye protection. The remediation technicians will construct engineering controls (a containment barrier) around the affected area to close-off unaffected areas from the remediation process. Slight negative air pressure should be maintained within the containment, with any air exiting the chamber also filtered through an air scrubber, to reduce the likelihood of cross-contamination of unaffected areas. Any wet and contaminated, porous materials, such as carpet or upholstered furniture, must usually be discarded. Materials to be discarded must be sealed in a container (such as a trash bag) while still within the containment area. Once removed from the building, it can be tossed out with typical construction waste.
Standing water must be extracted. Extraction is normally accomplished using a powerful portable unit or truck mounted vacuum unit that is capable of pulling a strong vacuum. Once standing water has been removed, any remaining residual moisture must be removed from materials to be saved through dehumidification. Refrigerant dehumidifiers are usually employed to reduce humidity levels. Conventional dehumidifiers are employed for small jobs operating near normal room temperature. Low grain refrigerant (LGR) dehumidifiers are used on small to medium size losses and higher moisture levels, as they are capable of discharging air at even lower humidity levels. However, to achieve maximum efficiency, refrigerant dehumidifiers must operate within a relatively narrow temperature range. Desiccant dehumidifiers are capable of achieving extremely low humidity levels in a wide range of temperatures, but they require a method to discharge moist air from the environment, which may not always be feasible, especially in the presence of mold. However, for large spaces desiccants may be the best and only option to maintain a regulated humidity level, especially in commercial and industrial environments.
When materials such as concrete or plaster become saturated with moisture, they can be difficult to dry, and will usually take much longer than materials such as wood, drywall or carpet. Heat may be added to the drying process in this case. However, heating the materials or the drying environment can also stimulate mold growth, and may not be the most practical tool to utilize in a mold job until humidity levels have been reduced below 50%. Air movement may also be applied to help in moisture removal, although this too is often curtailed in the presence of mold, to prevent spreading and cross-contamination.
It is not uncommon for the subfloor and structural members of a building to be contaminated with mold as well. Solid wood flooring or structural wood can be sanded or otherwise abraded to remove mold. HEPA vacuum equipment is employed to capture all of the dust and debris created by this process. The extent of material that must be removed will be specified in the protocol. Since sanding or grinding can compromise the integrity of some structural members, it may be necessary to consult with an engineer to decide how much material can be safely removed before having to be replaced.
The objective of a mold remediation is to return the indoor environment to normal, sanitary conditions. When the remediation protocol has been fully executed, the Industrial Hygienist will re-test the affected area to confirm whether the air and surfaces have been returned to pre-loss conditions. Sometimes further remediation and re-testing may be necessary. Once the remediation is complete, the containment barrier can be disassembled, and any reconstruction can begin.