Sick Building Syndrome (SBS) is a term used to describe a situation in which building occupants experience acute health effects or comfort issues that appear to be linked to the time spent in the building, with no specific illness or identified cause. SBS differs from Building Related Illness (BRI) because in BRI, the symptoms of diagnosable illness can be attributed to exposure to indoor air contaminants. SBS refers to nonspecific symptom complaints such as irritation of the throat, eyes, nose, and skin, headaches, and fatigue. These symptoms are felt by individuals while in their work space. The symptoms may worsen throughout the work day and disappear when they leave the work building.
The etiology of SBS is still not well understood, however there are several suspected causes linked to SBS. These causes may combine and supplement other comfort complaints such as temperature or relative humidity:
- Inadequate ventilation: In the 1970s the oil embargo pushed building designers to make buildings more airtight and reduce fresh air ventilation to improve energy efficiency. The amount of fresh air ventilation recommended then (5 cfm/occupant) is generally inadequate to maintain comfort. A ventilation rate of 15 cfm/occupant of fresh outdoor air is currently recommended to maintain comfort and health. HVAC systems may be unable to deliver adequate fresh air to a building, and this may result in SBS-like symptoms. Precisely measuring the amount of fresh air ventilation is not easy, and usually a surrogate measurement is made. The most common surrogate compound is carbon dioxide, since people exhale CO2 as part of normal respiration. Elevated CO2 levels may not be an absolute indicator of inadequate ventilation, but it is at least a good place to start. Determining whether there is a fresh air intake is also useful.
- Biological contaminants: Bacteria, viruses, molds, and pollen are included in this category. The contaminants may breed in stagnant water that has accumulated in drain pans and humidifiers, or in building materials such as insulation, gypsum board, and ceiling tiles subjected to elevated humidity. These contaminants can lead to cough, fever, chest tightness, and allergic reactions.
- Chemical contaminants: Most chemical air pollutants come from sources within the building. Carpeting, upholstery, adhesives, manufactured wooden products, copy machines, and cleaning agents may emit volatile organic compounds (VOCs). Environmental tobacco smoke is also a source of numerous VOCs and particulates. VOCs can cause both acute and chronic health effects including some cancers.
- Chemical contaminants from outdoor sources: Outdoor air that enters a building may contain contaminants that occupants may find irritating. These contaminants may include motor vehicle exhausts and building exhausts. This usually occurs when there are poorly located air intakes or other openings such as windows and doors. Garages that are adjacent to a building may also lead to combustion products entering the indoor environment.
When investigating potential causes of SBS, an investigator must determine if there is a building condition that may be related to a health complaint. The investigator must also identify the cause of the condition and recommend corrective actions. The investigation may include a walkthrough inspection of the building, compiling occupant complaints, inspection of the HVAC system, identifying potential contaminant pathways and sources, and measuring comfort parameters such as carbon monoxide, carbon dioxide, temperature and relative humidity.
Once potential contaminant sources are identified, there are several solutions available to help mitigate SBS symptoms:
- Remove or modify the contaminant: This is the most effective approach to resolving an indoor air quality problem when the source is known and it is feasible to control the source. Common mitigation measures include: Routinely replace loaded filters in the HVAC system; Use local exhaust ventilation at the contaminant source; Use solvents and cleaners during non-occupancy hours. These simple measures may have great effect in reducing SBS.
- Increase ventilation rates and air distribution: Increasing the amount of fresh air in the building may reduce SBS symptoms. Proper operation and maintenance of the HVAC system will likely go a long way in ensuring adequate fresh air exchanges. The HVAC system should be operated at its design standard and in accordance with ASHRAE Standard 62-1989 if possible.
- Air cleaners: These may be useful in supplementing other means of controlling indoor air quality issues. They are limited in scope and effectiveness, and are generally not sufficient on their own. For more information on air cleaners see our recent post: Do Air Purifiers Work?
- Education and communication: When everyone in the building fully communicates and understands the causes and consequences of indoor air quality issues, they can work together to prevent future issues that may coalesce as SBS. Building managers often ask us to conduct our inspection in off hours to keep a low profile. We have found that it is almost always more productive to conduct the inspection when folks are around. They can see that their concerns have been taken seriously, observe that something is getting done, and ask questions that frequently serve to reduce the level of hysteria that sometimes develops.
Sources:
EPA Indoor Air Facts No. 4 Sick Building Syndrome http://www.epa.gov/iaq/pdfs/sick_building_factsheet.pdf
National Safety Council: Sick Building Syndrome http://www.nsc.org/news_resources/Resources/Documents/Sick_Building_Syndrome.pdf