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| | 1/5/2009 11:03:20 PM |
More Moldy Oldies
Since our Garagram on mold a few months ago, we have had more questions about the topic. While there are thousands of molds with varying levels of destructiveness and danger, here are some general answers to some of the commonly asked questions about two of the worst offenders.
Stachybotrys chartarum (atra) is a slow growing mold that is greenish-black and slimy and is described as resembling tar or black paint. It is common on plant debris and in soil. It grows in high-cellulose, low nitrogen material, such as straw, hay, paper, fiberboard, lint, gypsum board (sheetrock), and wood. It will smear when touched. It grows in areas that are constantly wet. It will grow and reproduce from two to forty degrees C. It has been observed growing as soon as a week after a flood. Typical locations are leaky roofs, leaky plumbing, sewer backups, and frequently overflowing washing machines.
The mold will die when dried out, but it still will launch airborne spores when disturbed, even when dried. These spores are still allergenic and toxigenic. The mold spores are inhaled and then produce several toxins in the human body. Symptoms can mimic a cold or flu or exposure to other allergens. Adult symptoms include adverse effects on the central nervous system, irritated eyes, skin rash, respiratory tract irritations, immune suppression, bleeding, and possibly chronic fatigue. In children it can cause bleeding of the lungs, and is particularly deadly to infants.
Small scale contaminations (less than one square foot) can be abated by 1) eliminating the source of the water, 2) killing the mold with a solution of one cup of bleach in one gallon of water, 3) removal of the infected material, and 4) a thorough disinfecting of the surrounding areas. Care must be taken to not spread the mold when removing it, and eye, skin and breathing protection (HEPA respirator) should be utilized. Larger scale abatements should only be performed by qualified experts in full protective gear. These technicians will use similar equipment to that used in the asbestos abatement industry.
Poria incrassata is a fast growing brown–rot decaying fungus that devours wood. If ignored, this fungus can consume the underpinnings of an entire house in a single year. It is reported that it attacks pressure treated wood, cedar, juniper and redwood, as well as pine and oak. Infestations may occur within two years of major landscaping, leading to the speculation that infected soil was brought in for the landscaping. New houses are equally at risk, as well as remodel jobs, which may include lumber, which was infected while still in its forest state. Poria draws water through a large, tough root-like structure called a rhizomorph that allows it to siphon water even when the wood it infests is protected from moisture. These are irregular vine-like tubes, looking like a barkless root, that branch into the soil, or extend to some other constant source of moisture. These can be several meters in length and from six to twelve mm in diameter. They also can “crawl” as high as thirty feet. There are also “fan” structures of rhizomorphs that draw moisture directly from the air. Mature infestations sometimes form fruit bodies on the rotten wood. Poria resists many fungicides, especially those containing copper.
The rhizomorphs can move between very small openings, including cold joints between two concrete pours, as well as plumbing pipe penetrations of a typical slab-on-grade house. Because it requires water to grow, remediation is possible, if caught early enough. The first step is to remove the water source. After that, remove the rhizomorphs, and then the decayed wood, and then all the sound wood within 2 feet of the infestation. Poria is sensitive to drying and in laboratory tests, died in one day at 10 percent relative humidity, five days at 65 per cent relative humidity and ten days at 90 percent relative humidity. Poria is also sensitive to heat, which is why it seldom occurs in wood subjected to direct sunlight.
Case of the Month:
The case of the month deals with faint black streaks that formed on the interior walls of an office building. With a heightened awareness of the dangerous molds and mildews out there, (and sick building syndrome), we were called to inspect the building and report on the nature of the streaks and their cause and remediation.
Our expert noted that the building was constructed of steel framing with approximately six inches of fiberglass batting for insulation on the exterior walls. The attic had twelve inches of blown-in insulation. The windows were non-opening, leaving the door and perimeter air leaks as the only source of fresh air. Our expert carefully removed the paint and spackle over several sheet rock screws. There was no evidence of rusting on the heads and they removed with normal torque, indicating no rust along their length.
He cut a small section of sheetrock from the back wall and inspected the newly exposed cavity. There was no indication of excessive moisture, nor of any molds or mildews. He inspected the area around the heater/air conditioner. An employee of the office mentioned that seldom did they switch on the unit as most of the time it was not needed. He removed the filter and inspected it. It was quite coarse and there was no visible dust or lint on the filter surface. His final inspection was of the black streaks under a microscope. And what was the conclusion? Dust.
The exterior steel beams worked as conduits for the cold from the outside to come to the interior walls. The lack of air changes from the outside created a low make-up condition that caused respired moisture from the office employees to be retained in the office atmosphere. This moist warm air condensed on the cool sheet rock surfaces in the shape of the steel beams behind them. The fine dusts in the atmosphere were not filtered by the coarse air filter (which was seldom in use) and they collected on the cool moist surfaces of the walls. The solution: more air changes per hour and a better filter system.
Expert of the Month:
Our expert of the month holds a Master of Science in Environmental Sciences and a Bachelor of Science in Physics and Astronomy. He is a registered Safety Engineer, a Board Certified Industrial Hygienist, and a Board Certified Safety Professional. He investigates a variety of issues involving safety, occupational accidents, environmental assessment, hazardous materials, product liability, and general construction.
© Copyright 2009 The Miller Law Firm. All rights Reserved.
If you experience problems or have questions, contact us at Info@ConstructionDefects.com.
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