根據我多年與汙點戰鬥的經驗和總結, 我可以 有90%的把握告訴你,
因為冬天天冷關著門窗睡覺,潮氣在牆上聚集,形成了 黑黴點.
My easy solution: buy a bottle of ' Mould Away ’from ALDI store, around 3 dollars, and spray around the affected area.
Then wipe away with a piece of cloth.
Have a try. Easy, efficient, and effective.