When sourcing USB mini fans, prioritize brushless DC motors as they offer higher energy efficiency, lower noise levels (ideally under 30dB), and a significantly longer lifespan compared to brushed motors. Check the battery capacity (measured in mAh) for rechargeable models; a standard 2000mAh battery should provide 4-8 hours of operation. Additionally, verify the airflow speed settings (usually 3-speed) and the charging interface, ensuring it uses USB-C for modern compatibility and faster charging.