There is no scientific evidence to support the claim that onions can purify the air. While onions do release certain compounds when cut, which can give a strong smell that may temporarily mask other odors in the air, there is no evidence to suggest that these compounds have any significant air-purifying properties.
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To effectively purify the air in your house, it is recommended to use proven methods such as ventilation, air purifiers, or cleaning with natural products. Boiling herbs, mentioned in the available information, can release essential oils that may have some antibacterial or antiviral properties, but their effectiveness in purifying the air is still not well-established and may not be as effective as other methods.
Therefore, it is advisable to rely on scientifically proven methods for air purification, rather than depending on onions or herbal remedies alone.