Christmas candles: what happens to the air in your home when you light more than one

Scented candles are a holiday must-have, but we often underestimate the invisible risks they can pose to our health and the environment. Some scented candles can in fact negatively affect the quality of home air and, in some cases, have repercussions on health, but the risk substantially varies based on the type of candle and its use.

Concerns about the safety of candles arise from the chemical reactions that occur when they are lit, as well as the artificial fragrances and colorants that help create the various scents we love.

In recent years, experts have been shining a spotlight on domestic pollution: we spend up to 90% of our time indoors and even small sources of emissions, such as candles, become more relevant, especially in the winter months when many more are lit.

What happens when we light a candle

Candles, especially those made with paraffin wax, release volatile organic compounds (VOCs) during combustion. These include chemicals such as toluene and benzene, which are known for their potential harmful effects, primarily respiratory irritation.

Toluene, a clear, colorless vaporized liquid with a distinctive odor that occurs naturally in crude oil, is a toxin with exposure limits established by some regulatory agencies. This is because it is a neurotoxin associated with dizziness, headaches or more severe effects in case of prolonged exposures.

Benzene, a known carcinogen, is another VOC released by paraffin candles. Long-term exposure to this chemical has been linked to blood disorders such as leukemia. If inhaled, benzene is a respiratory irritant.

Scented or colored candles tend to release more toxins, including phthalates, which are associated with endocrine and respiratory problems. And consider that an April 2015 study, which simulated indoor use, showed that some candles could emit toxins even when they are turned off.

In addition to VOCs, combustion also produces fine particulate matter (PM2.5 and PM1) and soot, responsible for the classic blackening around candle holders and on walls. Ultrafine particles are particularly insidious because they remain suspended in the air for a long time and can easily penetrate the lungs. An unstable flame — caused by air currents or too long wicks — significantly increases the production of soot.

Are scented candles dangerous?

According to pulmonologist Dr. Sobia Farooq, associate professor at the Lerner College of Medicine at the Cleveland Clinic, there are not yet enough studies that lead to the unequivocal conclusion that all candles containing paraffin are harmful to health.

But the expert warns that risks still exist and may depend on various factors:

More drastic is the opinion of Dr. Sarah Evans, associate professor of environmental medicine and climate science at the Icahn School of Medicine at Mount Sinai, who told CNN:

A good number of studies have evaluated candle emissions in controlled environments and homes and have shown that burning candles contributes to poor air quality and increases the risk of inhalation exposure to chemicals of concern.

Candle companies often dismiss alarmist fears, claiming that the emissions released by a good-quality candle are comparable to those generated by common household activities, such as cooking. Some brands use highly refined paraffin with a very low content of impurities and fragrances that comply with IFRA standards, which set precise limits on the substances that can be used in fragrances.

How to reduce risks

If you don’t want to give up candles, there are some precautions you can take:

To further reduce emissions, it is useful to keep the wick trimmed to around 3–5 millimeters before each use: a shorter flame burns cleaner. Avoid leaving the candle lit for more than 3–4 consecutive hours and put it out with a snuffer instead of blowing, so as to limit residual smoke. Location matters too: keep candles away from drafts and in areas where the flame won’t be disturbed.

For those looking for a decorative effect without significant emissions, unscented natural wax candles remain the safest option. Catalytic lamps can purify the air and release light fragrances, but they must be used correctly to avoid unnecessary exposure. In many cases, simple decorative LED lights can replace traditional candles when you just want a cozy atmosphere without combustion.

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