Maintaining the home’s HVAC system is vital to keep it running efficiently and holding down energy costs. But is cleaning out the ductwork part of that strategy? It may surprise some homeowners and a few home inspectors to learn that the answer is a firm “maybe, maybe not.” Having the ductwork professionally cleaned may be an appropriate course of action if the system has been contaminated by moisture or mold, but, absent these issues, it may create more issues than it solves. A general amount of airborne dust in a home is normal; homeowners shouldn’t try to fix a problem that doesn’t exist. But before making any recommendations to your clients, read more about it in our six-part article series: The Home Inspector’s Guide to Air Duct Cleaning.
“The conditions that contribute to the health risk were summarized as follows.
- Microorganisms are ubiquitous. Microbes propagate rapidly wherever water is available. The dust and dirt normally present in most indoor spaces provide sufficient nutrients to support extensive microbial growth. While mould can grow on all materials, selection of appropriate materials can prevent dirt accumulation, moisture penetration and mould growth.
- Microbial growth may result in greater numbers of spores, cell fragments, alergens, mycotoxins, endotoxins, β-glucans and volatile organic compounds in indoor air. The causative agents of adverse health effects have not been identified conclusively, but an excess level of any of these agents in the indoor environment is a potential health hazard.
- Microbial interactions and moisture-related physical and chemical emissions from building materials may also play a role in dampness-related health effects.
On the basis of this review, the following guidelines were formulated.
- Persistent dampness and microbial growth on interior surfaces and in building structures should be avoided or minimized, as they may lead to adverse health effects.
- Indicators of dampness and microbial growth include the presence of condenation on surfaces or in structures, visible mould, perceived mouldy odour and a history of water damage, leakage or penetration. Thorough inspection and, if necessary, appropriate measurements can be used to confirm indoor moisture and microbial growth.
- As the relations between dampness, microbial exposure and health effects cannot be quantified precisely, no quantitative health-based guideline values or thresholds can be recommended for acceptable levels of contamination with microorganisms. Instead, it is recommended that dampness and mould-related problems be prevented. When they occur, they should be remediated because they increase the risk of hazardous exposure to microbes and chemicals.
- Management of moisture requires proper control of temperatures and ventilation to avoid excess humidity, condensation on surfaces and excess moisture in materials. Ventilation should be distributed effectively throughout spaces, and stagnant air zones should be avoided.
- Building owners are responsible for providing a healthy workplace or living environment free of excess moisture and mould, by ensuring proper building construction and maintenance. The occupants are responsible for managing the use of water, heating, ventilation and appliances in a manner that does not lead to dampness and mould growth. Local recommendations for different climatic regions should be updated to control dampness-mediated microbial growth in buildings and to ensure desirable indoor air quality.
- Dampness and mould may be particularly prevalent in poorly maintained housing for low-income people. Remediation of the conditions that lead to adverse exposure should be given priority to prevent an additional contribution to poor health in populations who are already living with an increased burden of disease.
- The guidelines are intended for worldwide use, to protect public health under various environmental, social and economic conditions, and to support the achievement of optimal indoor air quality. They focus on building characteristics that prevent the occurrence of adverse health effects associated with dampness or mould. The guidelines pertain to various levels of economic development and different climates, cover all relevant population groups and propose feasible approaches for reducing health risks due to dampness and microbibial contamination. Both private and public buildings (e.g. offices and nursing homes) are covered, as dampness and mould are risks everywhere. Settings in which there are particular production processes and hospitals with high-risk patients or sources of exposure to pathogens are not, however, considered.
- While the guidelines provide objectives for indoor air quality management, they do not give instructions for achieving those objectives. The necessary action and indicators depend on local technical conditions, the level of development, human capacities and resources. The guidelines recommended by WHO acknowledge this heterogeneity. In formulating policy targets, governments should consider their local circumstances and select actions that will ensure achievement of their health objectives most effectively.”