main circuit vent
/ˈmeɪn ˈsɜːkɪt ˈvɛnt/
n
English · main circuit vent中文 · 主通气立管Español · toma de aire principalFrançais · colonne de ventilation principale
意味：Vertical pipe vented directly outdoors that allows air to circulate throughout the draining circuit; it also vents sewer gas.