What is an air-purifying terrarium and how does it work?

An air-purifying terrarium is a self-sustaining ecosystem in a closed container that uses plants to remove toxins and pollutants from the air. Plants inside the terrarium absorb carbon dioxide and release oxygen, while also filtering out harmful substances, creating a healthier environment.

What plants are best for an air-purifying terrarium?

Good plant choices include ferns, mosses, ivy, bromeliads, snake plants, spider plants, and peace lilies, as they thrive in humid environments and are effective at removing pollutants like formaldehyde and benzene. Ensure the plants are small and slow-growing to fit well within the terrarium.

How do I build a DIY air-purifying terrarium?

Start with a clean, clear container, then add a drainage layer of gravel, followed by a layer of activated charcoal to filter impurities. Add a layer of soil, and then plant your selected air-purifying plants. Mist the terrarium and seal it, placing it in indirect sunlight.

How do I maintain my air-purifying terrarium?

Maintenance involves occasional misting with distilled water when the soil looks dry, and opening the lid for ventilation if there's excessive condensation. Prune any dead or overgrown plant material to keep the terrarium tidy and prevent mold. Ensure it receives indirect sunlight to avoid overheating.

How does a terrarium purify air, compared to a regular air purifier?

Terrariums purify air naturally using plants, which absorb pollutants and release oxygen, and they do not require electricity or chemicals. While less powerful than dedicated air purifiers, they offer an aesthetic and eco-friendly way to improve indoor air quality in a smaller area, combining decoration with air purification.

DIY Air Purifier

By Home Sidekick Team May 31, 2025 8 min read 1561 words

terrariumair purificationdiyindoor gardeningplantshome decor

Indoor air pollution is a growing concern. Studies show that indoor air can be more polluted than outdoor air (EPA, 1989). While commercially available air purifiers can be effective, they can also be expensive. A DIY air purifier offers an affordable and customizable alternative. This blog post explores how to create your own air purifier using readily available materials, focusing on the power of plants in a terrarium setting.

The Science Behind Air-Purifying Plants

Plants purify air through a process called phytoremediation. During photosynthesis, plants absorb carbon dioxide and release oxygen. However, their air-purifying abilities go beyond this basic exchange. Plants can also absorb harmful pollutants like formaldehyde, benzene, xylene, and trichloroethylene from the air (Wolverton, 1989). These chemicals are commonly found in household products, furniture, and building materials.

Formaldehyde: Found in pressed wood products, fabrics, and some glues.
Benzene: Released from paints, solvents, and gasoline.
Xylene: Used in rubber, leather, and printing industries; also found in paints and varnishes.
Trichloroethylene: Used in cleaning products and adhesives.

NASA conducted a Clean Air Study in the late 1980s, led by Dr. B.C. Wolverton, to identify plants suitable for improving air quality in space stations (Wolverton, 1989). The study highlighted several plants with excellent air-purifying capabilities. The roots and soil microorganisms play a crucial role in removing these pollutants, breaking them down into harmless substances that the plant can then use as food.

Selecting the Right Plants for Your DIY Air Purifier

Not all plants are created equal when it comes to air purification. Some are more effective at removing specific pollutants than others. Here are some of the best plants for a DIY air purifying terrarium:

Snake Plant (Sansevieria trifasciata): Excellent at removing formaldehyde, xylene, toluene, and nitrogen oxides. It also converts CO2 into oxygen at night, making it ideal for bedrooms.
Spider Plant (Chlorophytum comosum): Effective at removing formaldehyde and xylene. It's also easy to propagate, allowing you to create multiple air purifiers.
Peace Lily (Spathiphyllum wallisii): Filters formaldehyde, benzene, trichloroethylene, xylene, toluene, and ammonia. Note: Peace lilies are toxic to pets.
Boston Fern (Nephrolepis exaltata): A natural humidifier, the Boston Fern removes formaldehyde, xylene, and toluene. They require high humidity.
English Ivy (Hedera helix): Effective at removing benzene, formaldehyde, xylene, and toluene. Suitable for hanging terrariums.
ZZ Plant (Zamioculcas zamiifolia): Very low maintenance and removes xylene, toluene, and benzene.

Consider the growing conditions when choosing your plants. Snake plants and ZZ plants are drought-tolerant, while Boston ferns require consistently moist soil and high humidity. Match your plants to the environment you can provide for them to thrive.

Building Your DIY Air Purifying Terrarium

A terrarium creates a self-contained ecosystem that promotes plant growth and air purification. You can create either an open or closed terrarium. Open terrariums are suitable for plants that prefer drier conditions, while closed terrariums are ideal for humidity-loving plants.

Materials You'll Need:

Glass Container: A large glass jar, fishbowl, or terrarium container.
Gravel or Pebbles: For drainage.
Activated Charcoal: To filter toxins and odors (horticultural charcoal is preferred).
Potting Soil: A well-draining potting mix suitable for your chosen plants.
Air-Purifying Plants: Select 3-5 plants based on their air-purifying abilities and compatibility.
Sphagnum Moss (Optional): To separate the drainage layer from the soil.
Decorations (Optional): Small stones, driftwood, figurines, etc.
Spray Bottle: For watering.

Step-by-Step Instructions:

Prepare the Container: Clean the glass container thoroughly.
Add Drainage Layer: Spread a 1-2 inch layer of gravel or pebbles at the bottom of the container. This layer prevents water from pooling around the roots and causing root rot.
Add Activated Charcoal: Sprinkle a thin layer (about ½ inch) of activated charcoal over the gravel layer. This helps filter impurities and keep the terrarium fresh.
Add Sphagnum Moss (Optional): Place a thin layer of sphagnum moss on top of the charcoal to prevent the soil from mixing with the drainage layer.
Add Potting Soil: Add a layer of potting soil suitable for your chosen plants. The depth of the soil layer will depend on the root systems of your plants, typically 2-4 inches.
Plant Your Plants: Gently remove the plants from their pots, loosen the root balls, and plant them in the terrarium. Arrange them aesthetically, considering their mature size and growth habits.
Water Lightly: Use a spray bottle to lightly mist the soil. Avoid overwatering, as terrariums retain moisture.
Add Decorations (Optional): Arrange decorative elements like stones, driftwood, or figurines to create a visually appealing terrarium.
Find the Right Location: Place your terrarium in a location that receives bright, indirect sunlight. Avoid direct sunlight, which can overheat the terrarium.

Tips for Terrarium Success:

Choose the Right Soil: Use a well-draining potting mix to prevent waterlogging.
Avoid Overwatering: Terrariums retain moisture, so water sparingly. Allow the soil to dry slightly between waterings.
Provide Adequate Light: Most terrarium plants prefer bright, indirect sunlight.
Prune Regularly: Trim plants as needed to prevent them from overcrowding the terrarium.
Ventilate Occasionally: For closed terrariums, open the lid occasionally to allow fresh air to circulate and prevent excessive humidity.
Monitor for Pests: Inspect your plants regularly for signs of pests. Treat any infestations promptly with appropriate organic pest control methods.

Enhancing Air Purification: Additional Methods

While a plant-filled terrarium is a great start, you can further enhance its air-purifying capabilities with these additional methods:

Activated Carbon Filters:

Adding a small, battery-operated fan with an activated carbon filter can significantly boost the removal of airborne pollutants. Place the fan inside the terrarium (ensure it is safe for humid environments) or near the terrarium to draw air through the filter. Activated carbon is incredibly porous, providing a large surface area to trap pollutants (ATSDR, 1995).

HEPA Filters:

While a full-sized HEPA filter isn't practical inside a terrarium, placing a small HEPA filter air purifier near your terrarium can work synergistically. The plants will remove many common pollutants, and the HEPA filter will capture fine particles like dust, pollen, and pet dander (EPA, 2018).

Optimizing Plant Density:

The more plants you have, the greater the air-purifying potential. Consider creating multiple terrariums or incorporating more plants into your existing terrarium (while ensuring they have enough space to thrive). A higher plant density translates to more surface area for pollutant absorption.

Maintaining Your DIY Air Purifier

Regular maintenance is essential to keep your DIY air purifier functioning optimally.

Watering:

Water your terrarium only when the soil feels dry to the touch. Overwatering can lead to root rot and fungal growth. Use a spray bottle to evenly moisten the soil.

Fertilizing:

Terrarium plants generally require very little fertilizer. Fertilize sparingly, using a diluted liquid fertilizer specifically formulated for houseplants, about once every 2-3 months during the growing season (spring and summer).

Cleaning:

Wipe down the inside of the glass container periodically to remove condensation and algae buildup. This will improve light penetration and prevent fungal growth.

Replacing Activated Charcoal:

Replace the activated charcoal layer every 6-12 months to maintain its effectiveness. Over time, the charcoal becomes saturated with pollutants and loses its filtering capacity.

Repotting:

As your plants grow, they may outgrow the terrarium. Repot them into larger containers or propagate them to create new terrariums.

Troubleshooting Common Terrarium Problems

Even with careful maintenance, you may encounter some common terrarium problems.

Cloudy Glass:

Excessive condensation can cause the glass to become cloudy. This is usually a sign of overwatering or poor ventilation. Open the terrarium lid to allow excess moisture to evaporate and reduce watering frequency.

Mold Growth:

Mold growth is often caused by excessive humidity and poor air circulation. Remove any visible mold and improve ventilation by opening the terrarium lid more frequently. Ensure good drainage and avoid overwatering.

Yellowing Leaves:

Yellowing leaves can indicate several problems, including overwatering, underwatering, nutrient deficiency, or pest infestation. Adjust your watering schedule, fertilize sparingly, and inspect for pests.

Leggy Growth:

Leggy growth (long, spindly stems) is usually a sign of insufficient light. Move your terrarium to a brighter location or supplement with artificial light.

Conclusion: Breathe Easier with a DIY Air Purifier

Creating a DIY air purifying terrarium is a rewarding project that combines the beauty of nature with the practical benefits of cleaner indoor air. By selecting the right plants, building a well-draining terrarium, and providing proper care, you can create a self-sustaining ecosystem that removes harmful pollutants and improves your indoor environment. This project is not only cost-effective but also promotes a deeper connection with nature. Take the first step towards cleaner air today and build your own DIY air purifier! Consider experimenting with different plant combinations and decorative elements to create a unique and personalized air-purifying oasis.

Next Steps:

Research different air-purifying plants to find those that best suit your needs and environment.
Gather the necessary materials and tools.
Follow the step-by-step instructions to build your terrarium.
Monitor your terrarium regularly and make adjustments as needed.
Share your creation with friends and family and encourage them to build their own DIY air purifiers.

References

Agency for Toxic Substances and Disease Registry (ATSDR). (1995). Toxicological Profile for Carbon Tetrachloride. Atlanta, GA: U.S. Department of Health and Human Services, Public Health Service.
EPA. (1989). Report to Congress on Indoor Air Quality: Volume 1. EPA/400/1-89/001A. U.S. Environmental Protection Agency, Washington, DC.
EPA. (2018). Guide to Air Cleaners in the Home. U.S. Environmental Protection Agency, Washington, DC.
Wolverton, B. C., Johnson, A., & Bounds, K. (1989). Interior landscape plants for indoor air pollution abatement. NASA.