Essential oil diffuser affecting indoor air quality

How Essential Oils Worsen Indoor Air Quality

All essential oils emit volatile organic compounds (VOCs)1. VOCs are organic chemicals that have a high vapor pressure at room temperature, which allows them to evaporate or sublimate easily and enter the air as gases.

The specific VOCs and their concentrations vary widely among different essential oils2, depending on the plant source, the part of the plant used, and the method of extraction. These compounds can range from being completely natural (as is the case with essential oils) to synthetic VOCs found in various household products.

While the term “VOCs” often carries negative connotations associated with industrial pollutants and synthetic chemicals that can be harmful to health and air quality, not all VOCs are hazardous. In the case of essential oils, many of the VOCs are natural compounds such as terpenes (e.g., limonene, pinene), alcohols (e.g., linalool, menthol), and esters (e.g., linalyl acetate), which can have beneficial properties, including antimicrobial and therapeutic effects.

However, even natural VOCs from essential oils can contribute to indoor air pollution and may pose health risks3 when inhaled in large amounts or over extended periods, especially in poorly ventilated spaces. Some individuals may experience allergic reactions, respiratory issues, or other health effects from exposure to certain VOCs, regardless of whether they are naturally occurring or synthetic. Therefore, it’s important to use essential oils judiciously and ensure adequate ventilation when diffusing them indoors to minimize potential health risks.

Types of Essential Oil Diffusers

When evaluating the impact of different types of essential oils and diffusers on indoor air quality, several factors come into play, including the method of diffusion, the type and amount of volatile organic compounds (VOCs) released into the air, and any potential particulate matter or other byproducts produced during the diffusion process. Here’s a brief overview of each type and their potential impact on indoor air quality:

  1. Nebulizing Essential Oil Diffusers: These diffusers work by using pressurized air to disperse essential oils into fine droplets without the use of heat or water. They can release a more concentrated fragrance and a higher concentration of essential oils into the air. Because of this, they might contribute significantly to the VOCs in the indoor environment, which in excessive amounts can affect air quality.
  2. Ultrasonic Essential Oil Diffusers: Ultrasonic diffusers use water and ultrasonic vibrations to create a fine mist of water/oil that is released into the air. They can increase humidity in a room because they disperse a mixture of water vapor and oil. This could be beneficial in dry environments but might contribute to mold growth in more humid settings. The VOC concentration from these diffusers might be lower compared to nebulizing diffusers due to the dilution with water.
  3. Heat Essential Oil Diffusers: These diffusers use heat, either electric or from a candle, to evaporate and disperse essential oils into the air. The heat can alter the chemical composition of the essential oils, potentially reducing their therapeutic properties and possibly generating harmful compounds depending on the oils used and the heating method. However, the impact on indoor air quality may vary widely based on the type of heat used and the level of ventilation in the room.
  4. Evaporative Diffusers: These diffusers work by evaporating the essential oils into the air, typically using a fan to blow air through a filter or pad that has essential oils on it. The rate of evaporation and dispersal can be slower and less intense than other types of diffusers, potentially leading to a lower overall impact on indoor air quality in terms of VOC concentration.

Diffusers Impact on IAQ

In terms of worsening indoor air quality, nebulizing diffusers may pose the greatest risk because they can disperse a high concentration of VOCs into the air without dilution. High levels of VOCs can contribute to health problems, especially in poorly ventilated areas or among individuals with sensitivities or respiratory issues. However, the actual impact can vary based on how often and how long the diffuser is used, the specific essential oils diffused, and the size and ventilation of the indoor space.

It’s essential to use all types of essential oil diffusers with caution, ensuring adequate ventilation and following the manufacturer’s guidelines to minimize potential negative impacts on indoor air quality.

Air Quality Concerns with Essential Oils

The safety and impact of essential oils on indoor air quality depend on their chemical composition, the presence of volatile organic compounds (VOCs), and how they interact with the air and surfaces within an indoor environment.

Safer Essential Oils for Indoor Air Quality

  • Lavender: Known for its calming effects, lavender oil is generally considered safe and has been used in various settings without significant negative impacts on air quality. It has antimicrobial properties, which can be beneficial.
  • Tea Tree: This oil has strong antimicrobial properties, potentially improving indoor air quality by reducing airborne bacteria when used in moderation.
  • Eucalyptus: Often used for its respiratory benefits, eucalyptus can be safe when diffused in small quantities. It may help clear airways and has antimicrobial properties.
  • Peppermint: With its refreshing scent, peppermint is another oil that can be safe for indoor air when used in moderation. It also has antimicrobial properties.

These “safer” oils should be used sparingly, especially in environments with pets, children, pregnant women, or individuals with respiratory conditions, as they can be sensitive to even small amounts of essential oils. While some of these may be safe in moderation, any oil used in excess can be dangerous.

Essential Oils Potentially Worse for Indoor Air Quality

  • Citrus Oils (e.g., Lemon, Orange): While they have a refreshing scent and antimicrobial properties, citrus oils contain compounds like limonene4, which can react with ozone in the air to form formaldehyde, a known irritant and carcinogen.
  • Pine and Spruce Oils: These oils can also react with airborne chemicals, forming potentially harmful substances that can contribute to indoor air pollution.
  • Cinnamon, Clove, and other “spicy” oils: These oils contain eugenol and other compounds that can be irritating to the airways in some individuals and may contribute to indoor air quality issues if used in large amounts or in poorly ventilated areas.

General Recommendations

It’s best to avoid using essential oil diffusers completely if IAQ is your main priority. However, if you decide using essential oils is best for you, here are a few safety recommendations.

  • Use in Ventilation: Ensure good ventilation when diffusing essential oils to prevent buildup of any potentially harmful compounds.
  • Quantity Matters: Use smaller amounts of essential oils, as excessive use can lead to a higher concentration of VOCs in the air, which might be harmful over time.
  • Sensitive Groups: Be cautious around pets, children, pregnant women, and people with asthma or other respiratory conditions, as they may be more sensitive to the effects of diffused oils.
  • Quality of Essential Oils: Use high-quality, pure essential oils without synthetic additives, as these are safer and less likely to produce undesirable effects when diffused.

It’s crucial to remember that safety can vary based on individual sensitivities, the specific brand and quality of the essential oil, and how it’s used within the home. High-quality, pure essential oils with clear sourcing are generally safer, but moderation is key. And it’s important to monitor for any adverse reactions when using essential oils around sensitive individuals or in shared spaces.


  1. This general statement about VOCs emitted by essential oils can be supported by Nematollahi et al. (2018), who examined volatile chemical emissions from a range of commercial essential oils, identifying a wide variety of VOCs including potentially hazardous ones emitted from these oils. [Nematollahi et al. Volatile chemical emissions from essential oils[1]. 2018]
  2. Soualeh & Soulimani (2016) provide insights into the diversity and roles of volatile organic compounds in essential oils, emphasizing their natural occurrence and potential therapeutic properties, as well as the need to consider their safety [Soualeh & Soulimani. Plant essential oils and volatile organic compounds: roles and interests[2]. 2016]
  3. This study (2007) specifically investigates the effects of evaporating essential oils on indoor air quality, noting increases in CO, CO2, and total VOC levels, and highlights the antimicrobial activity of certain essential oils like tea tree oil while also pointing out the potential health risks due to high emissions of specific terpenes. [H. Su, Chung-Jen Chao, Ho‐Yuan Chang, Pei-Chih Wu. The effects of evaporating essential oils on indoor air quality[3]. 2007]
  4. González-Mas et al. (2019) provided a comprehensive review of volatile compounds in citrus essential oils, illustrating the vast diversity of VOCs in citrus species and their implications for food and perfume industries. The review also highlights the need for careful consideration of these compounds due to their potential effects on health and the environment [González-Mas et al. Volatile Compounds in Citrus Essential Oils: A Comprehensive Review[4]. 2019].


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  1. Nematollahi, N., Kolev, S. D., & Steinemann, A. (2018, August 8). Volatile chemical emissions from essential oils. Air Quality, Atmosphere & Health. Springer Science and Business Media LLC.
  2. (n.d.). Plant essential oils and volatile organic compounds: roles and interests | Semantic Scholar. Retrieved from
  3. (n.d.). ScienceDirect. Retrieved from
  4. González-Mas, M. C., Rambla, J. L., López-Gresa, M. P., Blázquez, M. A., & Granell, A. (2019, February 5). Volatile Compounds in Citrus Essential Oils: A Comprehensive Review. Frontiers in Plant Science. Frontiers Media SA.
Owner / FounderDerek Gaughan
Derek is the owner and lead content producer for Air Koality. His primary focus is on reviewing residential air quality monitors and air purifiers. An alumni of Pennsylvania State University, he holds a Bachelor’s Degree in Information Sciences and an MBA with a focus on Information Systems. He also completed The EPA Indoor Air Quality (IAQ) Master Class Professional Training, in addition to passing the Mainstream IAQ certification.

Expertises: air quality, IAQ
Lead Editor (IAQ), Clinical BacteriologistJessica Gunoskey
Jessie is the lead editor for Air Koality, overseeing all IAQ guides to ensure accuracy and quality. She holds a degree in Molecular & Infectious Disease Biology from Washington College in addition to working for multiple top-rated universities, such as UConn and UPenn. Not only does she write and edit, but she also is a STEM tutor and microbiologist!

Expertises: microbiology, infectious disease, biology, air quality

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