Which type of vapor recovery system is commonly used in underground storage tanks (USTs)?

The correct answer is Stage II vapor recovery systems, which are specifically designed for use at fuel dispensing stations where fuel is transferred from storage tanks to fuel vehicles. These systems operate when fuel is being pumped into vehicles, capturing the vapors that are displaced during the fueling process and preventing them from being released into the atmosphere.

Stage II vapor recovery systems specifically address the emissions that occur at the point of sale, where the public interacts with the fuel dispensing equipment. This is crucial in urban areas with higher air quality concerns, as it helps to minimize volatile organic compounds (VOCs) from entering the atmosphere, contributing to smog and other environmental issues.

Understanding this, a Stage II system, which focuses on capturing vapors at the point of transfer, distinguishes it from the other types of vapor recovery systems. Stage I vapor recovery systems are primarily concerned with controlling vapors released during the loading of fuel into the storage tanks, whereas enhanced vapor recovery systems aim to improve the efficiency of vapor recovery systems in general and may be implemented in more modern or upgraded setups. Sealed vapor recovery systems, while effective in some contexts, do not reflect the specific application needed for vapor recovery during vehicle refueling at USTs.

Therefore, the differentiation of vapor recovery capabilities and their