What no candles!? – Things to consider before burning candles in your home

Candles mark special occasions and create a special atmosphere. They also bring fire and chemicals into the home so their use needs to be carefully considered. At a time when candles are more popular than the days when Thomas Edison was burning the midnight oil inventing the light bulb it is common for tenancy agreements to have ‘no candles’ clauses. Why should this be so? Key reasons why burning candles in the home may not be a good idea:

1. Risk of fire
2. Damage to decoration
3. Air pollution

Looking at each of these in turn..

Fire
According to the Fire Service in the year 2000 alone, there were over 2,000 house fires due to candles. As a result, 10 people died and over 900 were injured. As the sales of candles grows, this trend is unfortunately set to continue. In our own area there have been a number of recent fires involving candles and tea lights – thankfully some were only minor but in one fire the house was completely destroyed after a candle set light to the curtains. Candle safety advice can be found here: http://www.fireservice.co.uk/safety/candles

Damage
Black soot is the product of the incomplete combustion of carbon-containing fuels. Until recently, the source of black soot in homes was unknown but recent research suggests that frequent candle burning is one of the sources. Complete combustion results in a blue flame, and would produce negligible amounts of soot and carbon monoxide. The amount of soot produced can vary greatly from candle to candle. One type of candle can produce as much as 100 times more soot than another type. The type of soot may also vary; though primarily composed of elemental carbon, candle soot may include phthalates, lead, and volatiles such as benzene and toluene.

Black Soot Deposition (BSD) is also referred to as ghosting, carbon tracking, carbon tracing, and dirty house syndrome. Complaints of BSD have risen significantly in recent years and have been the subject of libel cases in the USA.
Scented candles are a major cause of BSD. Most candle wax paraffins are saturated hydrocarbons that are solid at room temperature. Most fragrance oils are unsaturated hydrocarbons and are liquid at room temperature. The lower the carbon-to-hydrogen ratio, the less soot is produced by the flame. Therefore, waxes that have more fragrances in them produce more soot. In other words, candles labelled “super scented” and those that are soft to the touch are more likely to generate soot.

The situation in which a candle is burned can also impact its sooting potential. A small and stable flame has a lower emission rate than a larger flickering flame with visible black particle emissions. A forced air flow around the flame can also cause sporadic sooting behaviour. Thus, candles in glass containers produce more soot because the container causes unsteady air flow and disturbs the flame shape. Candles that are extinguished by oxygen deprivation, or blowing out the candle, produce more soot than those extinguished by cutting off the tip of the wick. Cutting the wick eliminates the emissions produced by a smouldering candle.

When soot builds up in air, it eventually deposits onto surfaces due to one of four factors. First, the particle may randomly collide with a surface. Second, soot particles can be circulated by passing through home air-conditioning filters. Third, soot can gain enough mass to become subject to gravity. Finally, the particles are attracted to electrically charged surfaces such as freezers, vertical plastic blinds, television sets, and computers. Homes suffering from BSD commonly have stained carpets particularly where the carpet meets the walls and under doors and shadows (ghosting) where walls meet ceilings.
In one of the worst examples we have seen, a tenant moved into a brand new property locally. The tenant loved burning aromatic candles – a well-known brand available in all supermarkets. After 6 months all surfaces in the property including walls, ceilings and cupboards were coated in a greasy grey layer of soot. As many of the surfaces were semi-porous, the entire property had to be deep cleaned and re-painted – the ghosting on the carpets remains!
Heat and hot wax from candles can also cause damage. In one property we observed a smouldering tea light which had melted the plastic holder beneath and had welded to and scorched the furniture beneath (which was not the tenants!).

Air Pollution
When candles are burned, they emit trace amounts of organic chemicals, including acetaldehyde, formaldehyde, acrolein and naphthalene. However, the primary constituent of health concern in candle emissions is lead. Metal was originally put in wicks to keep the wick standing straight when the surrounding wax begins to melt. The metal prevents the wick from falling over and extinguishing itself as soon as the wax fails to support it. Although lead wicks in candles were banned in the UK in 2003 there may still be lead wick candles on the market. Consider also the airborne candle soot which is subject to inhalation. The particles can potentially penetrate the deepest areas of the lungs, the lower respiratory tract and alveoli.

Further Reading: http://nepis.epa.gov/Adobe/PDF/P1009BZL.pdf
The odd birthday candle is going to carry little risk of fire, damage or air pollution but you may want to consider the long-term effects of burning candles in your home.

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