R. Morse, D. Zehnter, P. Haas, A. Grdina, Morse Zehnter Associates, Poestenkill, NY.
This paper reports on a study of over 100 buildings that were experiencing mold contamination due to elevated levels of relative humidity. Temperatures and relative humidity were logged for a 1 week period at 10 locations in each building. Occupants were interviewed to evaluate subjective determinations of temperature and humidity problems. The HVAC equipment was inspected and its conditions and operating parameters were documented. In each building the causes of the high relative humidity were determined. Corrective action needed to reduce humidity in the conditioned spaces was determined and costs of corrective actions determined.
A number of lessons have been learned from this study that will be described in this paper. The causes of high relative humidity in air-conditioned buildings have been defined and documented. Typically, high humidity was found to be caused by excessive ventilation air, oversized equipment, overwarm coils, and improper operation of HVAC equipment under part-load conditions. However, less obvious causes such as modulating chilled water valves, negative pressure, envelope problems, and improperly mixed outside air were also found to be problems. Practical field measuring and surveying methods have been developed to evaluate HVAC equipment for these problems. Careful analysis of temperature and relative humidity logs was found to be a powerful and practical diagnostic tool. The interpretation of these logs will be described. The physical symptoms of mold contamination caused by high humidity have been determined. In many instances these symptoms can be diagnostic of high humidity during a walk-around evaluation before measurements are taken. Building occupants were found to be very tolerant of high humidity levels. Frequently, complaints were registered only when there were other indoor air quality problems such as musty odors, or there was visible mold present.
M. McGuinness, R.K. Occupational and Environmental Health, Phillipsburg, NJ.
Situation: A hotel complex was inundated by 3 feet of sea water. The primary concern was widespread microbiological contamination. This project involved restorative drying of the first floor, removal of bulk water and porous materials, disinfecting and decontaminating remaining surfaces, removal of moldy building materials, and reconstruction. Reoccupancy criteria were developed that placed a premium on disinfecting impacted areas and drying the structure.
Problems: Category 3 water is defined by the Institute of Inspection, Cleaning, and Restoration Certification (IICRC) publication S-500 Standard and Reference Guide for Professional Water Damage Restoration as water which “arises from large quantities of sewage entering a structure.” This category also includes all forms of sea water, surface water, and rising water from rivers or streams. Category 3 water is assumed to contain parasites, viral and/or bacterial pathogens, and other potential microbiological health hazards.
Resolution: Inasmuch as this project involved decontaminating a facility impacted by Category 3 water, certain generally-accepted procedures were specified. These procedures were developed from cleaning and restoration industry standards and generally accepted public health procedures. Remedial procedures were designed to protect remedial workers and future occupants. Close-out procedures included visual inspection, sampling for microbials, and a moisture evaluation.
This case study is presented with the intention of introducing those industrial hygienists not familiar with IICRC protocols to their Standard S-500. This document is recognized as the standard of care for addressing water losses in the cleaning and restoration industry. It is also considered the “de facto” standard for addressing water infiltration in litigation and insurance circles. Finally, it is considered by the author to be a useful, state-of-the-art reference for remediation of water-damaged facilities.
W. Sothern, Micro Ecologies Inc., New York, NY.
Why has mold suddenly become a major health issue, and consequently a major media, legal, and insurance issue? The reason can be summarized in two words: Stachybotrys and sheetrock.
Sheetrock became the primary building material for interior walls and ceilings during the 1950s, and today its use continues undiminished. Awareness of the Stachybotrys-sheetrock connection grew dramatically following the SoHo Museum incident and the issuance of the highly respected NYC DOH Guidelines for the Assessment and Remediation of Stachybotrys atra in 1993. As our housing stock ages, water damage from plumbing problems and rainwater infiltration will only worsen. Therefore, we can expect Stachybotrys-driven mold issues to be with us for many decades to come.
Over the past 10 years, I have performed over 2,000 IEQ investigations of New York City area residential dwellings where problem levels of mold growth were identified. The prevalence of Stachybotrys growth on recurrently water-damaged sheetrock exceeds 90% based on data analysis of 100 of our recent IEQ investigations, and these results are consistent with our previous experience.
If we are to diffuse the current mold crisis, we must remove sheetrock from areas likely to experience water damage. The industrial hygienist can help accomplish this in many important ways, including: writing scopes of work for mold abatement projects that advise against using sheetrock on rebuilds, and recommend using cement board and other good material substitutions; advising architects, contractors, and homeowners against using sheetrock in basements, plumbing chases, walls containing plumbing fixtures, mechanical room walls, and at the base of fan-coil units; working with local and state governments to change building codes; and training building maintenance personnel to inspect for, prevent, and safely respond to mold problems.
C. Robbins, S. Swenson, M. Krause, W. Geer, GlobalTox Inc., Redmond, WA; P. Fallah, Environmental Microbiology Laboratory, San Diego, CA.
Industrial hygienists are often asked to assess sources of mold exposure in indoor environments. Visual inspection is usually the most important aspect in determining whether mold is present. Wet gypsum wallboard (GWB) is often a site of visible growth indoors. Often, questions arise such as how long does it take before visible mold appears after GWB is wet, how quickly does the surface become covered with mold growth, what effect does treatment with paint or mold inhibiting products have on the rate and extent of mold growth, and what types of mold occur in what time frame? This study begins to answer these questions. Standard ½” GWB was obtained from a typical building supply store. Each piece was cut into two, 2’ x 8’ sections. One piece of each pair was treated as follows: 1) untreated; 2) painted on one side with one coat of Kilz™ primer; 3) coated on one side with Fosters 20-40™; and, 4) treated on one side with Borocare™. The sister side was left untreated. The bottom of each piece remained resting in approximately 1” of distilled water; the water level was checked and replenished every 24 hours. (A dry control was handled like the four treatments, except for the water.) Materials were maintained in a normal office-type environment, with typical office temperature, humidity, and light cycles, for a period of 2 months. Each section was photographed and examined daily, and measurements were recorded of mold surface area coverage and of a sample of colony sizes. Ambient temperature and humidity were monitored. Weekly samples were collected from each wallboard treatment and submitted for analysis of mold types present. Data are presented as to when visible mold growth is first observed, the extent of visible mold growth, mold species identified, and the effect of treatments on these parameters.
J. Kominsky, Environmental Quality Management Inc., Cincinnati, OH; J. Luckino, Archatas Inc., Worthington, OH; T. Martin, PEMCo Inc., Worthington, OH.
A newly-constructed single-family structure was vacated due to mold-related health concerns reported by the occupants. An investigation by the homeowners’ consultant postulated that the elevated microbial burden in the house was due to mold in the building envelope. Infrared thermography was used to identify potential areas of high moisture in the building envelope and to identify areas that required further investigation by invasive inspection to establish a theory of what was causing the moisture, as well as the extent of the resultant microbial contamination. Infrared thermography is a nondestructive process by which electromagnetic radiation given off by objects is captured in a visual image by a radiometric infrared camera. A Thermovision® 550 camera was used in this study. To minimize the effects of the sun, the thermography was performed at night.
The building exterior was mostly brick veneer with synthetic stucco. Thermographic images identified 11 areas on the south, east, and north elevations where moisture was potentially collecting in the building envelope. At each location the brick veneer was removed to expose the method of brick installation and the composition of the envelope. The exterior sheathing was removed to expose the framework, batt insulation, vapor barrier, and backside of the gypsum wallboard. Observations were photographed, moisture was measured by a moisture measurement system, and bulk samples were collected for culture analysis.
Excessive moisture (>20% free water content) and microbial colonization were present in the wall components at 7 of the 11 test sites, with 1 site showing significant deterioration to the oriented-strand board sheathing. Four of the 11 test sites showed elevated moisture (15–19%). The moisture gained access through capillary action, and the water shedding ability of the mortar and brick had been compromised by excessive acid cleaning of the masonry.
P. Morey, Air Quality Sciences Inc., Gettysburg, PA; E. Horner, B. Ligman, Air Quality Sciences Inc., Atlanta, GA; K. Abe, Institute of Environmental Biology, Aikou-gun Kanagawa, Japan.
Fungal detectors or biosensors are tiny devices, approximately 13 mm by 50 mm and 1 mm thick, containing viable spores placed on a plastic plate covered with a water vapor permeable membrane so that water vapor can diffuse in or out but the spores cannot exit. The fungal detectors used in this study contained spores of Eurotium herbariorum, Alternaria alternata, and Aspergillus penicillioides. Detectors were used quantitatively by calculating a fungal index by comparison to the growth of Eurotium herbariorum during a 7-day period at 25°C and 93.6% relative humidity (RH). The study objective was to see if fungal detectors were useful to building inspectors in determining if moisture conditions were adequate to support mold growth. Fungal detectors were deployed in building microenvironments or on interior surfaces with current or past moisture problems. The xerophilic fungi E. herbariorum and A. penicillioides grew in detectors in damp microenvironments or on damp surfaces. The same xerophilic fungi failed to germinate or grow in buildings that had successfully undergone adequate restorative drying. The hydrophilic fungus A. alternata grew in wet (RH>95%) microenvironments. Periodic and consistent decline of RH to 60% or less in otherwise humid microenvironments appeared to inhibit spore germination in detectors. While fungal detectors will not replace the standard uses of dew point and moisture meters, the detectors provide inspectors with an additional tool for investigating mold growth problems in buildings.
Posted May 30, 2004