Like many holiday traditions, lighting candles and fireplaces is best done in moderation

The warm spices of gingerbread, the woody aroma of pine and fir trees and the fruity taste of mulled wine are smells synonymous with the end of year celebrations. Many people enjoy lighting candles, incense, and fireplaces in their homes to evoke the moods associated with these festive scents.

Burning scented products can create a cozy ambiance and, in the case of fireplaces, provide light and warmth, but some experts want people to think about how it helps indoor air quality. All flames release chemicals that can cause allergy-type symptoms or contribute to long-term respiratory problems if inhaled in sufficient quantities.

However, people don’t have to stop sitting near the fireplace or get rid of products like scented candles and essential oil diffusers, said Dr. Meredith McCormack, director of the division of pulmonary and critical care medicine at John Hopkins University School of Medicine. Instead, she recommends taking precautions to control pollutants in their homes.

“Clean air is fragrance-free,” said McCormack, who has studied air quality and lung health for more than 20 years. “If having seasonal scents is part of your tradition or evokes feelings of nostalgia, think about it in moderation.”

People in the Northern Hemisphere tend to spend more time indoors during the holiday season, when temperatures are colder. Indoor air can be much more polluted than outdoor air because pollutants remain trapped indoors and concentrated without proper ventilation or filtration, according to the American Lung Association.

For example, active fireplaces and gas appliances release tiny airborne particles that can enter the lungs and chemicals like nitrogen dioxide, a major component of smog, according to the U.S. Environmental Protection Agency. Cleaning products, air fresheners and candles also emit air pollutants in varying concentrations.

The risk that fragrances and other air pollutants can pose to respiratory health depends on the source, duration and intensity of a person’s exposure, as well as individual health, McCormack said.

It’s also important to note that some pollutants don’t have an odor, and unscented products can still affect indoor air quality, experts say.

Polluted air affects everyone, but not in the same way. Children, older adults, minority populations and people of low socioeconomic status are more likely to be affected by poor air quality due to physiological vulnerabilities or higher exposure, according to the environmental agency.

Children are more susceptible to air pollution because of the size of their lungs, meaning they are more exposed to pollution relative to their body size, McCormack said. Pollutants inside the home also pose a greater risk to people with heart or lung disease, including asthma, she said.

Signs of respiratory irritation include coughing, shortness of breath, headache, runny nose and sneezing. Experts advise stopping the use of polluting products or immediately ventilating the rooms if symptoms appear.

“The more risk factors you have, the more harmful air pollution or poor indoor air quality can be,” McCormack said.

Ellen Wilkowe burns vanilla and cinnamon-scented candles when she does yoga, writes, or takes a shower at her home in New Jersey. Her teenage daughter, for her part, prefers candles scented according to the seasons, like gingerbread.

“Candles have a calming presence. They are also very symbolic and used in rituals and in many religions,” she said.

Wilkowe said she prefers candles made with soy-based waxes rather than petroleum-based paraffin. Experts note that all lit candles release air pollutants, regardless of their composition.

Buying products with fewer ingredients, opening windows if temperatures permit and using air purifiers with HEPA filters are ways to reduce exposure to pollutants from indoor fireplaces, appliances and candle displays, McCormack said. She also recommends turning on kitchen exhaust fans before starting a gas stove and using the rear burners so the vent can more easily suck up pollutants.

Setting polite limits on guests who smoke cigarettes or other tobacco products is also a good idea, she said.

“Small improvements in air quality can have measurable health benefits,” McCormack said. “In the same way, if we exercise and eat a little better, we can be healthier.”

Rachael Lewis-Abbott, a member of the Indoor Air Quality Association, an organization of professionals who identify and resolve air quality problems, said people usually don’t notice what they are breathing until problems such as gas leaks or mold develop.

“It’s out of sight, out of mind,” she said.