Regarding photoionization devices (PIO) at WMD or hazmat incidents, which statement is correct?

• A. They do not identify the material present.
• B. They identify the material present.
• C. They detect carbon monoxide.
• D. They are effective for hydrogen cyanide.

Answer: (A)

Photoionization devices work by using UV light to ionize molecules that have relatively low ionization energies. The current produced in the detector correlates to the concentration of ionizable volatile organic compounds in the air. But that signal does not tell you which chemical is present; it only indicates that VOCs are present and gives a rough level. That means these instruments identify the presence of VOCs in general, not the specific material.

Because of how they detect, they’re not reliable for substances like carbon monoxide or hydrogen cyanide, which aren’t effectively ionized by the common PID energies or aren’t VOCs. To determine the exact substance, you’d need a different method or confirmatory analysis (such as GC-MS or FTIR).