Soot and IAQ environments. (Technical Briefs).

Candle burning, often used to enhance ambience through scent and sight, is now considered a possible culprit of ghosting-or black staining--on the interiors of buildings. Candles release soot which may then outline furniture; stain walls, carpets and fabrics; and damage artwork.

Soot is the black carbon residue resulting from incomplete combustion. Its particles range in size from 0.3 to 3 microns and can remain aerosolized for hours before settling. Soot deposition can indicate a faulty HVAC system or poor building design and may pose a health hazard. It may also be mistaken for mold growth.

Good airflow and exchange rates help prevent ghosting. Conversely, black soot deposition could indicate a problem with air handling. Unbalanced air flows and incorrectly engineered or leaky HVAC systems may result in spillage of vented air inside the building (California Environmental Protection Agency [CEPA], 1994;) as well as introduce automobile exhaust or other fumes from the garage (Vigil, 1998) or building exterior. Spillage can in turn lead to ghosting, elevated moisture levels (CEPA) and mold growth. Identifying and correcting air-handling deficiencies is an important step in a quality remediation solution. The soot source and its location also must be considered.

In addition. to candles, vehicle exhaust, incense, cooking, pilot lights, tobacco products, and space heaters can produce soot. Depending on the concentration, source, and composition of the soot, exposure can have deleterious health effects. The black carbon of soot can combine with other toxic organic compounds emitted during combustion such as polycyclic aromatic hydrocarbons (PAHs) (Stephen, 2002), which have been found to be carcinogenic (Stephen; Vermont Public Interest Research Group, 2000-2002).

It is not known conclusively that soot from candle burning is hazardous to human health. A U.S. Environmental Protect Agency (U.S. EPA) publication has summarized the results of three candle-burning emission tests. In a worst-case scenario, acetaldehyde, formaldehyde, and acrolein were found to reach levels that may indicate concern in an indoor air quality context, depending on interpretation (U.S. EPA, 2001).

Soot, especially from candle burning, is becoming a more significant factor in IAQ consulting and remediation. It can damage property and may be a health concern, Proper remediation should distinguish soot deposition from mold growth and consider both the soot source and its driver.

References:

California Environmental Protection Agency Air Resource Board. (1994). Combustion pollutants in your home. Indoor Air Quality Guideline No. 2. www.arb.ca.gov/research/indoor/combustf.htm (2 Oct. 2002).

Vigil, F. (Jan/Feb 1998). Black stains in houses: Soot, dust, or ghosts? Home Energy Magazine. http://www.homeenergy.org/archive/hem.dis.anl.gov/eehem/98/980109.htm l (2 Oct. 2002).

Stephen, F.D., Stineman, C.H., Jonmaire, P.W., Kelly, D.W., & Harbison, R.D. (2002). Risk analysis of candle emissions. http://www.litigation.support.ene.com/candle_emissions.htm (2 Oct. 2002).

Vermont Public Interest Research Group. (2000-2002). Environmental health effects of diesel engines, http://www.vpirg.org/campaigns/environmentalHealth/dieselExhaust.html (2 Oct. 2002).

U.S. EPA (2001). Chapter 4: Potential indoor air quality impacts of burning candles and incense. Candles and incense as potential sources of indoor air pollution: Market analysis and literature review. EPA-6001R-01-001. http://www.epa.gov/ORG/NRMRL/Publications/600R-01-001%20Chapter%204.p df (2 Oct. 2002).