When selecting a portable vacuum cleaner, the most critical metric is Suction Power, typically measured in Pascals (Pa); for handheld units, look for at least 5,000Pa to 8,000Pa for effective debris removal. Additionally, evaluate the Battery Capacity (mAh) and Runtime, ensuring a minimum of 20-30 minutes of continuous operation on a single charge. For filtration, prioritize models equipped with HEPA Filters (H13 grade) to ensure 99.97% of fine dust particles are captured, which is a major selling point for health-conscious consumers.