Which of the following is a common source of VOCs indoors?

Volatile Organic Compounds (VOCs) are organic chemicals that can easily evaporate at room temperature and are commonly found in various indoor environments. Among the given options, paints and cleaning products are significant sources of VOCs indoors.

When paints and cleaning products are used, they can release VOCs into the air as they dry or are applied. These compounds can contribute to various indoor air quality issues, such as eye, nose, or throat irritation, headaches, and even long-term health effects with prolonged exposure. Common VOCs found in these products include formaldehyde, toluene, and benzene, which are all linked to both short-term and long-term health risks.

In contrast, rainwater, candle wax, and outdoor air are not typical sources of VOCs found indoors. Rainwater is generally safe and does not emit VOCs itself. Candle wax can produce some VOCs when burned, but this is typically not a primary concern compared to the substantial emissions from paints and cleaning products. Outdoor air may contain VOCs but generally serves as a reference point rather than an indoor source since the question specifically asks for indoor sources. Thus, the option relating to paints and cleaning products is the most accurate and relevant choice.