Which of the following is a common source of VOCs?

Volatile Organic Compounds (VOCs) are emissions that can originate from various materials and substances typically found in indoor environments. In this context, plywood stands out as a common source of VOCs due to the adhesives and finishes that are frequently used in its manufacture. These materials often contain VOCs, which can be released into the air over time, particularly when the plywood is new.

In contrast, concrete, brick, and steel are generally considered less significant sources of VOCs. While concrete might emit some compounds during curing, it does not produce VOCs in the same amounts as plywood. Similarly, brick is primarily made from clay and minerals, which do not release VOCs. Steel, being a metal, is also inert in this respect and does not emit VOCs. Therefore, plywood is identified as the most relevant choice among the options provided for a common source of VOCs in indoor environments.