Christmas trees and VOCs: The source of that fresh, clean holiday smell

Every holiday season, Americans buy nearly 30 million live Christmas trees. Many households cherish the scent of pine that drifts through their halls. The fragrance, which is often described as crisp and woodsy, can set a cheerful tone. Yet there is much more to this refreshing aroma.

That fresh smell comes from substances known as volatile organic compounds, or VOCs. These are airborne chemicals that can be released by a wide range of items inside a home.

Fresh paint, cleaning solutions, and newly purchased furniture all have distinct VOC profiles that contribute to the atmosphere we breathe.

Research and its driving force

“Our nose is a good chemical sensor,” said Dustin Poppendieck, an environmental engineer at the National Institute of Standards and Technology (NIST).

“We know that these trees are emitting something, and the question then becomes: How big of a source is it? We wanted to explore which chemicals are emitted and how much, and to put that into the context of other sources of chemicals in a house.”

In a recent study, he and his colleagues took a Douglas fir and enclosed it in a specialized chamber. The team wanted to gauge which compounds lingered and how they might shift in a controlled environment. They kept track of the emissions for 17 days to gather a clear picture.

VOCs in the home

VOCs appear in many household products and activities. They come from cleaners, new carpeting, varnishes, personal care items, and similar sources. Some have a pleasant smell that appeals to people, while others cause throat irritation and watery eyes for those who are sensitive.

Many manufacturers now produce items with fewer VOCs, including paint labeled as low-emission. People are also more aware of how indoor air quality impacts overall well-being, so they weigh their choices when buying scented or chemical-based goods. Even simple habits, like regularly airing out rooms, can help manage exposure.

Christmas tree in a chamber

In the experiment, the researchers placed a decorated tree inside a chamber designed to mimic typical indoor conditions. The lights switched on and off every 12 hours, outside air came in at a realistic pace, and the tree was watered each day.

A specialized instrument called proton-transfer reaction mass spectrometry tracked airborne compounds in real time. This method offers a detailed look at changing levels of chemicals in the air.

The researchers observed which specific compounds were released during the first few days and how quickly they dropped as time went on.

A closer look at the scent

Monoterpenes emerged as the primary source of the tree’s signature aroma. These molecules also show up in fragrant products such as certain air fresheners and scented candles. They spiked early in the study, before tapering off within the first 72 hours.

According to the measurements, the initial concentration of monoterpenes equaled levels found in a freshly built house or a newly opened plug-in air freshener. From there, the emissions dropped by nearly tenfold.

The scientists noted that 52 different types of monoterpenes appeared, illustrating how varied these natural compounds can be.

Christmas trees and ozone

The team also introduced ozone to see if it would interact with the tree’s emissions. Ozone near ground level can form through chemical reactions triggered by light. Outdoors, it has been linked to coughing and throat irritation when levels become elevated.

In the chamber, ozone caused monoterpenes to transform into new byproducts. One of these compounds was formaldehyde, measured at about one part per billion in this setup. That number is much smaller compared to the 20 to 30 parts per billion typically found in U.S. houses.

Indoor air perspectives

For some individuals, the rush of VOCs from a freshly displayed tree can lead to mild respiratory responses. The watery eyes or runny nose often show up during the initial phase when emissions peak. Opening a window can help if these symptoms arise.

Outside of that, the changes in indoor air chemistry did not reach levels likely to raise alarms. The data indicated that although there was a clear spike in certain compounds, normal ventilation methods were effective at dispersing them.

Simple steps to avoid issues

People who prefer a newly cut tree might consider leaving it outside or in a garage for about three days before setting it up indoors. The intensity of monoterpene emissions falls naturally during that waiting period, which can lessen any initial surge.

Keeping doors or windows ajar, especially when first moving the tree into a living area, also allows any lingering chemicals to escape. These small adjustments may help families enjoy a traditional tree without worrying about minor discomforts.

Context for the season

The investigators pursued this research to fill knowledge gaps about how natural decorations might affect indoor air. The study, published in the journal Indoor Environments, highlights the dynamic relationship between conifer emissions and everyday living spaces.

Beyond Douglas fir trees, many items in our homes give off VOCs that shape the air we breathe. Recognizing the major sources can guide practical ways to manage them, whether through better ventilation or careful selection of household products.

Awareness of indoor air quality

For those concerned about VOCs, the biggest wave of tree-related emissions occurs early on. Poppendieck advises airing out the living area if irritation becomes noticeable. He also notes that storing the tree for a bit in a cooler spot often eases the transition.

“But for most people, this shouldn’t be a major concern. I’m still going to have a Christmas tree in my house,” said Poppendieck.

For some, the fresh scent of a real tree remains a part of the season. Awareness of indoor air quality tips can keep the experience enjoyable.

The full study was published in the journal Indoor Environments.

—–

Like what you read? Subscribe to our newsletter for engaging articles, exclusive content, and the latest updates.

Check us out on EarthSnap, a free app brought to you by Eric Ralls and Earth.com.

—–