Which instrument is commonly used to detect volatile organic compounds (VOCs) in air at a scene?

• A. Gas Chromatography
• B. Flame Ionization Detector
• C. Photoionization Detector
• D. Infrared Gas Sensor

Answer: (C)

Rapid field screening of volatile organic compounds relies on a detector that ionizes a wide range of organic vapors with UV light to produce a measurable signal. A photoionization detector does exactly this: it uses ultraviolet photons to ionize many VOCs present in the air, and the resulting electrical current is proportional to the VOC concentration. This makes it a fast, portable, real-time tool ideal for incident scenes where responders need immediate information about VOC presence and relative levels. It can detect solvents, fuels, and many common industrial organics across a broad spectrum, which is what you want for quick situational awareness.

Gas chromatography, while highly capable for separating and identifying individual compounds, is a laboratory or benchtop technique and not suitable for rapid on-scene screening. A flame ionization detector is a type of detector used with chromatography; it requires a GC system to operate and isn’t a standalone handheld instrument for field use. An infrared gas sensor can identify certain gases by their infrared absorption, but it’s typically more selective and may miss many VOCs or be affected by environmental factors, making it less suitable for broad, rapid VOC screening at a scene.