When the weather is less than cheery, it’s appealing to hunker down and set a cosy scene by lighting a candle. With shorter days and freezing temperatures, staying in becomes a default.
Making that choice feel desirable rather than a necessity has become a ritual for many of us.
But beyond the calm, gentle flickering and scented notes wafting through the air, there is increasing understanding about how burning a favourite candle contributes to invisible pollutants that circulate through your home’s
air.
Candle emissions are tiny particles and gases released as a candle burns. Studies have shown candle burning can contribute to indoor air pollution through the emission of combustion-related pollutants.
“These include nitrogen dioxide (NO₂), tiny particles known as ultrafine particles, and chemicals called polycyclic aromatic hydrocarbons (PAHs), some of which are linked to health risks,” explains Karin Rosenkilde Laursen.
A Postdoctoral fellow in Public Health at Aarhus University in Denmark, Rosenkilde Laursen has carried out research into health effects following short-term exposure to indoor ultrafine particles from both cooking and candles.
Particle emissions released from candles
Her research found that while both candles and cooking emit high levels of particles, the number of particles from candles was much higher. Even more significant was the difference in particle size: cooking produced
particles about 80 nanometers wide, whereas candles generated particles around seven to eight nanometers in size – much smaller and much easier for our lungs to inhale.
“Once there, they may settle in lung tissue or pass into the bloodstream, allowing them to reach vital organs such as the heart and brain. This can trigger biological responses like inflammation and oxidative stress, which
over time have been linked to chronic conditions including respiratory and cardiovascular disease, and possibly cancer.”
The particles are invisible to the human eye and more than a thousand times thinner than a human hair. They can remain airborne for long periods, and when candles are blown out, the concentration of these particles (including soot) increases even further.
Individuals with certain conditions should always pay close attention to any and all potential air pollution exposures and do what they can to minimise them such as ensuring adequate ventilation. According to
Rosenkilde Laursen, this includes children, the elderly, pregnant women and people with chronic lung conditions like asthma or chronic obstructive pulmonary disease (COPD).
“They are far more sensitive to particulate air pollution – hence, they should be more careful.”
It is sometimes claimed natural forms of wax such as soy or beeswax are safer and healthier than paraffin. However Rosenkilde Laursen says all candles still produce ultrafine particles and gases when burned. She believes
what’s sometimes overlooked is how the overall impact also depends heavily on how the candle burns, not just the wax.
For example, ensuring wicks are well trimmed, and candles are placed away from draughts that will cause flickering help control how well the candle burns. ‘Stressed burning’ such as a candle placed in an area with disturbed air will produce more soot. A long or poorly trimmed wick also produces a larger, unstable flame and more soot.
Snuff that flame out
Many brands sell wick trimmers that look like long-handle scissors to help keep wicks at the right height.
Burning your candle all the way across the first time will also avoid wax ‘tunnelling’ where wax builds up around the sides of the container, creating a narrow hole down the centre. This ensures a candle burns evenly and efficiently.
Using a metal snuffer to extinguish the flame rather than blowing out also helps reduce carbon particles spread into the air.
More commonly referenced safety concerns include keeping a candle well away from any flammable items, but also the impact excessive heat may have on glass vessels. There have been incidences of candles shattering without warning, sending hot wax and glass shards across the room. With this in mind, never leave a candle burning for an extended period.
Many high-end candles are manufactured with glass designed for candle use, but with the abundance of cheaper options now available, there is no guarantee this has been taken into consideration.
There are no specific mandatory safety standards for candles in Australia and New Zealand, other than a ban on candles with lead wicks containing more than 0.06% lead.
Given the recent attention to these challenges, candle lovers have been exploring alternatives to burning, to enjoy scented wax candles.
What is a candle warmer?
The popularity of candle warmers and candle lamps was initially largely contained to teens, many of whose parents were concerned about open flames in bedrooms, but the range and accessibility of these
products is quickly growing.
Designed to melt scented candles without using an open flame, instead of lighting a wick, the device gently heats the wax, either from below with a warming plate or from above with a lamp,
releasing fragrance into the air. This way the candle lasts longer because the wax evaporates more slowly compared to burning. It remains unclear if there are any associated ultrafine particles emitted, but the approach eliminates issues like smoke, soot and uneven melting.
A similar idea is the use of wax melts –small, scented pieces of wax without a wick that release fragrance when gently heated in an electric warmer. Popular Aotearoa-based candle brand Ecoya has just launched an Electric Wax Melter as well as wax melt refills created with its most popular fragrances, such as French Pear and Sweet Pea & Jasmine.
For those wanting a more subtle room fragrance, candle brands such as Glasshouse, Dusk and Jo Malone London also offer reed diffusers. The porous reed sticks made from rattan or bamboo soak up scented oil from a vessel and release it into the air through evaporation, lasting for several months.
Battery-operated LED candles also can help set the scene beautifully.
How to burn a candle safely
If you’re burning candles, follow these safety guidelines.
Trim the wick
Trim the wick and ensure it is upright before every use, keeping it around 6mm to prevent large flames, smoke, and soot.
Ventilate the room
Don’t use a candle in an enclosed space. If you can, open a window or ensure airflow, but avoid placing a candle near a draft. Keep it away from windows, fans, or air vents to prevent uneven burning and flare-ups. Once
the candle is extinguished, air out the room if possible for at least 10 minutes.
Limit burn time
Burn for no more than three hours at a time (always check manufacturer’s guidance) and let the wax melt evenly across the surface on the first burn.
Discard before the wax is gone
Discontinue burning when approximately 1cm of wax remains to help avoid glass overheating. Do not use if glass is cracked, chipped or broken.
Never leave unattended
Always extinguish before leaving the room, especially around children or pets.
Place safely
Use a stable, heat-resistant surface and keep your candle away from flammable materials to prevent fires
