What definition describes a gas released through the evaporation or incomplete combustion of fossil fuels and other organic chemicals?

• A. Secondary Pollutant
• B. Volatile Organic Compound (VOC)
• C. Primary Pollutant
• D. Particulate Matter

Answer: (B)

Gas released through evaporation or incomplete combustion of fossil fuels and other organic chemicals are volatile organic compounds. These are organic chemicals that readily vaporize into the air at room temperature due to their high vapor pressure. They originate from sources like solvents, fuels, paints, and other organic products, and when they evaporate or burn incompletely they emit gases into the atmosphere. This fits the concept of VOCs, which are emitted directly as vapors from these processes.

Secondary pollutants, in contrast, form in the atmosphere after reactions of emitted substances, not from the initial evaporation described here. Particulate matter refers to tiny solid or liquid particles, not gases. While some VOCs can be emitted as part of broader pollution, the specific mechanism in the definition—evaporation or incomplete combustion of organic chemicals—best matches volatile organic compounds.