Citronella candles are primarily known for deterring mosquitoes and other flying insects in outdoor settings. This leads many people to wonder if they can bring that bug-repelling convenience inside their homes. Using citronella candles indoors is complex, involving the inherent risks of burning any candle in an enclosed space and the specific properties of the concentrated essential oil they contain. Evaluating safety requires a close look at the combustion byproducts and the effects of concentrated citronella fumes on indoor air quality.
Understanding General Candle Combustion Risks
Burning any candle indoors introduces potential pollutants into the enclosed environment. Candle combustion produces fine particulate matter, often visible as soot, which can travel deep into the lungs and exacerbate respiratory conditions like asthma. Particulate matter increases when the wick is untrimmed or the candle flickers excessively.
Candles also release volatile organic compounds (VOCs), which are chemicals that easily vaporize at room temperature. Trace quantities of irritants like toluene and benzene can be emitted into the air, contributing to a decline in indoor air quality.
A further risk is the production of carbon monoxide (CO), an odorless gas, especially when a candle is burned in a room with poor ventilation. Using candles for extended periods or using multiple candles simultaneously allows these combustion gases to accumulate. Paraffin-based waxes are often associated with higher emissions of soot and certain VOCs compared to natural waxes like soy or beeswax.
Specific Concerns Regarding Citronella Oil Fumes
The addition of citronella oil introduces unique health concerns when the candle is burned indoors. Citronella is a concentrated essential oil, and when heated and combusted, the resulting fumes act as a potent indoor irritant. Inhaling these concentrated vapors can lead to symptoms such as coughing, throat irritation, and headaches, particularly in sensitive individuals.
People with pre-existing respiratory conditions, such as allergies or asthma, may experience a worsening of symptoms due to the strong, concentrated fumes. Excessive or prolonged inhalation of concentrated citronella oil can be unsafe, with some reports linking it to possible lung damage. The smoke produced by citronella candles can also be heavier than ordinary candles, exacerbating air quality issues.
Small children and household pets, especially birds and small mammals, are particularly vulnerable. Because of their smaller body mass and differing respiratory systems, the exposure risk to these concentrated combustion byproducts is significantly higher for them.
Why Citronella Candles Are Ineffective Indoors
Citronella candles function as a repellent by releasing a strong scent that masks the carbon dioxide and lactic acid humans emit, which are the primary attractants for mosquitoes. Outdoors, this scent creates a protective barrier because the smoke and fragrance are dispersed by air currents. The effectiveness relies on the continuous dispersion of this scent barrier.
In a closed indoor environment, the mechanism fails because the scent cannot be adequately dispersed to create a functional barrier. Instead, the fumes become highly concentrated, creating the health hazards previously mentioned. The candle does not eliminate insects already present; it merely saturates the air with smoke.
The lack of natural air movement indoors means the smoke and volatile compounds linger, increasing the risk of respiratory irritation. For the limited number of insects likely to be inside a home, the combustion risks far outweigh the minimal repellent utility.
Recommended Safe Indoor Alternatives
For managing indoor insects without compromising air quality, non-combustible methods offer safer and more effective solutions.
Mechanical Barriers
Mechanical barriers, such as ensuring all windows and doors have well-maintained screens, are the most straightforward approach to preventing insect entry. Physically removing an insect that has entered, often with a simple cup and paper, also avoids chemical exposure.
Electric Diffusers
If a scent-based repellent is desired, a safe alternative is to use citronella or other insect-repelling essential oils, such as lemon eucalyptus or peppermint, in an electric diffuser. Electric diffusers aerosolize the oil without burning it, avoiding the production of soot, CO, and combustion-related VOCs. These devices allow the aroma to be released at a lower, controlled concentration.
Traps and Air Movement
Electric insect traps, like UV light zappers or sticky traps, provide another non-combustion method for managing flying pests. These devices physically attract and capture or eliminate the insects without adding pollutants to the air. Using indoor fans can also help deter flying insects by creating air turbulence that makes it difficult for them to fly and land.